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The Dynamics of Disability: Measuring and Monitoring Disability for Social Security Programs (2002)

Chapter: Conceptual Issues in the Measurement of Work Disability

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Suggested Citation:"Conceptual Issues in the Measurement of Work Disability." Institute of Medicine and National Research Council. 2002. The Dynamics of Disability: Measuring and Monitoring Disability for Social Security Programs. Washington, DC: The National Academies Press. doi: 10.17226/10411.
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Suggested Citation:"Conceptual Issues in the Measurement of Work Disability." Institute of Medicine and National Research Council. 2002. The Dynamics of Disability: Measuring and Monitoring Disability for Social Security Programs. Washington, DC: The National Academies Press. doi: 10.17226/10411.
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Suggested Citation:"Conceptual Issues in the Measurement of Work Disability." Institute of Medicine and National Research Council. 2002. The Dynamics of Disability: Measuring and Monitoring Disability for Social Security Programs. Washington, DC: The National Academies Press. doi: 10.17226/10411.
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Suggested Citation:"Conceptual Issues in the Measurement of Work Disability." Institute of Medicine and National Research Council. 2002. The Dynamics of Disability: Measuring and Monitoring Disability for Social Security Programs. Washington, DC: The National Academies Press. doi: 10.17226/10411.
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Suggested Citation:"Conceptual Issues in the Measurement of Work Disability." Institute of Medicine and National Research Council. 2002. The Dynamics of Disability: Measuring and Monitoring Disability for Social Security Programs. Washington, DC: The National Academies Press. doi: 10.17226/10411.
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Suggested Citation:"Conceptual Issues in the Measurement of Work Disability." Institute of Medicine and National Research Council. 2002. The Dynamics of Disability: Measuring and Monitoring Disability for Social Security Programs. Washington, DC: The National Academies Press. doi: 10.17226/10411.
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Suggested Citation:"Conceptual Issues in the Measurement of Work Disability." Institute of Medicine and National Research Council. 2002. The Dynamics of Disability: Measuring and Monitoring Disability for Social Security Programs. Washington, DC: The National Academies Press. doi: 10.17226/10411.
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Suggested Citation:"Conceptual Issues in the Measurement of Work Disability." Institute of Medicine and National Research Council. 2002. The Dynamics of Disability: Measuring and Monitoring Disability for Social Security Programs. Washington, DC: The National Academies Press. doi: 10.17226/10411.
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Suggested Citation:"Conceptual Issues in the Measurement of Work Disability." Institute of Medicine and National Research Council. 2002. The Dynamics of Disability: Measuring and Monitoring Disability for Social Security Programs. Washington, DC: The National Academies Press. doi: 10.17226/10411.
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Suggested Citation:"Conceptual Issues in the Measurement of Work Disability." Institute of Medicine and National Research Council. 2002. The Dynamics of Disability: Measuring and Monitoring Disability for Social Security Programs. Washington, DC: The National Academies Press. doi: 10.17226/10411.
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Suggested Citation:"Conceptual Issues in the Measurement of Work Disability." Institute of Medicine and National Research Council. 2002. The Dynamics of Disability: Measuring and Monitoring Disability for Social Security Programs. Washington, DC: The National Academies Press. doi: 10.17226/10411.
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Suggested Citation:"Conceptual Issues in the Measurement of Work Disability." Institute of Medicine and National Research Council. 2002. The Dynamics of Disability: Measuring and Monitoring Disability for Social Security Programs. Washington, DC: The National Academies Press. doi: 10.17226/10411.
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Suggested Citation:"Conceptual Issues in the Measurement of Work Disability." Institute of Medicine and National Research Council. 2002. The Dynamics of Disability: Measuring and Monitoring Disability for Social Security Programs. Washington, DC: The National Academies Press. doi: 10.17226/10411.
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Suggested Citation:"Conceptual Issues in the Measurement of Work Disability." Institute of Medicine and National Research Council. 2002. The Dynamics of Disability: Measuring and Monitoring Disability for Social Security Programs. Washington, DC: The National Academies Press. doi: 10.17226/10411.
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Suggested Citation:"Conceptual Issues in the Measurement of Work Disability." Institute of Medicine and National Research Council. 2002. The Dynamics of Disability: Measuring and Monitoring Disability for Social Security Programs. Washington, DC: The National Academies Press. doi: 10.17226/10411.
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Suggested Citation:"Conceptual Issues in the Measurement of Work Disability." Institute of Medicine and National Research Council. 2002. The Dynamics of Disability: Measuring and Monitoring Disability for Social Security Programs. Washington, DC: The National Academies Press. doi: 10.17226/10411.
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Suggested Citation:"Conceptual Issues in the Measurement of Work Disability." Institute of Medicine and National Research Council. 2002. The Dynamics of Disability: Measuring and Monitoring Disability for Social Security Programs. Washington, DC: The National Academies Press. doi: 10.17226/10411.
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Suggested Citation:"Conceptual Issues in the Measurement of Work Disability." Institute of Medicine and National Research Council. 2002. The Dynamics of Disability: Measuring and Monitoring Disability for Social Security Programs. Washington, DC: The National Academies Press. doi: 10.17226/10411.
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Suggested Citation:"Conceptual Issues in the Measurement of Work Disability." Institute of Medicine and National Research Council. 2002. The Dynamics of Disability: Measuring and Monitoring Disability for Social Security Programs. Washington, DC: The National Academies Press. doi: 10.17226/10411.
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Suggested Citation:"Conceptual Issues in the Measurement of Work Disability." Institute of Medicine and National Research Council. 2002. The Dynamics of Disability: Measuring and Monitoring Disability for Social Security Programs. Washington, DC: The National Academies Press. doi: 10.17226/10411.
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Suggested Citation:"Conceptual Issues in the Measurement of Work Disability." Institute of Medicine and National Research Council. 2002. The Dynamics of Disability: Measuring and Monitoring Disability for Social Security Programs. Washington, DC: The National Academies Press. doi: 10.17226/10411.
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Suggested Citation:"Conceptual Issues in the Measurement of Work Disability." Institute of Medicine and National Research Council. 2002. The Dynamics of Disability: Measuring and Monitoring Disability for Social Security Programs. Washington, DC: The National Academies Press. doi: 10.17226/10411.
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Suggested Citation:"Conceptual Issues in the Measurement of Work Disability." Institute of Medicine and National Research Council. 2002. The Dynamics of Disability: Measuring and Monitoring Disability for Social Security Programs. Washington, DC: The National Academies Press. doi: 10.17226/10411.
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Suggested Citation:"Conceptual Issues in the Measurement of Work Disability." Institute of Medicine and National Research Council. 2002. The Dynamics of Disability: Measuring and Monitoring Disability for Social Security Programs. Washington, DC: The National Academies Press. doi: 10.17226/10411.
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Suggested Citation:"Conceptual Issues in the Measurement of Work Disability." Institute of Medicine and National Research Council. 2002. The Dynamics of Disability: Measuring and Monitoring Disability for Social Security Programs. Washington, DC: The National Academies Press. doi: 10.17226/10411.
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Suggested Citation:"Conceptual Issues in the Measurement of Work Disability." Institute of Medicine and National Research Council. 2002. The Dynamics of Disability: Measuring and Monitoring Disability for Social Security Programs. Washington, DC: The National Academies Press. doi: 10.17226/10411.
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Suggested Citation:"Conceptual Issues in the Measurement of Work Disability." Institute of Medicine and National Research Council. 2002. The Dynamics of Disability: Measuring and Monitoring Disability for Social Security Programs. Washington, DC: The National Academies Press. doi: 10.17226/10411.
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Suggested Citation:"Conceptual Issues in the Measurement of Work Disability." Institute of Medicine and National Research Council. 2002. The Dynamics of Disability: Measuring and Monitoring Disability for Social Security Programs. Washington, DC: The National Academies Press. doi: 10.17226/10411.
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Conceptual Issues in the Measurement 1 of Work Disability Alan M. Jette, Ph.D., and Elizabeth Badley, M.D.2 The field of disability research is in need of uniform concepts and a common language to guide scholarly discussion, to advance theoretical work on the disablement process, to facilitate future survey and epide- miological research, and to enhance understanding of disability on the part of professionals as well as the general public. A commonly under- stood language can also influence the development of public policy in the area of work disability, the focus of the Institute of Medicine’s workshop titled “Survey Measurement of Work Disability.” The current lack of a uniform language and commonly understood definition of the concepts of “disability” and “work disability” is a serious obstacle to all these endeavors. Conceptual confusion is a particular barrier to the improvement of the Social Security Administration’s (SSA) process for determining eligi- bility for both Social Security Disability Insurance (SSDI) and Supplemental Security Income (SSI) related to “work disability,” as was illustrated in the earlier Institute of Medicine workshop, “Measuring Functional Capacity and Work Requirements.” A shared language and conceptual understand- 1This paper was originally prepared for the committee workshop titled “Workshop on Survey Measurement of Work Disability: Challenges for Survey Design and Method” held on May 27–28, 1999, in Washington, D.C. (IOM, 2000). 2Alan Jette is a Professor and Dean of the Sargent College of Health and Rehabilitation Sciences at Boston University. Elizabeth Badley is Director of the Arthritis Community Research & Evaluation Unit at the University Health Network in Toronto, Ontario. 183

184 THE DYNAMICS OF DISABILITY ing did not emerge from that workshop. If various participants in the disability benefit determination revision process cannot agree on the mean- ing of the term “work disability,” they can hardly be expected to reach agreement on an approach to improving the work disability determina- tion process. The Social Security Act defines disability as the “inability to engage in any substantial gainful activity by reason of a medically determinable physical or mental impairment which can be expected to result in death or can be expected to last for a continuous period of not less than 12 months.” As this background paper will illustrate, this definition in the Social Security Act is at odds with most contemporary thought about the con- cept of disability and is in itself a barrier to the SSA’s work disability revision process. The paper aims to provide the reader with a conceptual foundation to facilitate discussion at the upcoming workshop titled “Survey Measure- ment of Work Disability.” Our intent is to highlight issues regarding lan- guage and concepts directly or indirectly related to the concept of “work disability.” To do so, we focus on several activities: 1. present a review of some of the contemporary definitions of dis- ability found in the literature; 2. discuss these definitions in the context of several major disable- ment frameworks; 3. discuss the concept of “work disability” in the context of these disablement models and relate it to other health-related phenom- ena; 4. critically review the conceptual basis of frequently used survey items that attempt to assess “work disability”; and 5. highlight some of the pressing research needs in the area of “work disability.” THE CONCEPT OF DISABILITY A common understanding of the term “disability” is an essential first step to a scholarly exchange about the concept of “work disability” and is the foundation for a fruitful discussion of improving survey research in the general area of disability and, more specifically, in the area of work disability. Understanding of the source of contemporary conceptual confusion requires a review of the major disability frameworks found in the litera- ture. The goal of bringing together the several different schools of thought on disability and the disablement process remains elusive. Achieving a

CONCEPTUAL ISSUES IN THE MEASUREMENT OF WORK DISABILITY 185 commonly accepted conceptual language is one of the primary challenges facing the field of disability research. Major Schools of Thought Several schools of thought have defined disability and related con- cepts. We will focus on the Disablement Model developed by Nagi (1965) and the International Classification of Impairments, Disabilities, and Handicaps (ICIDH-1) (WHO, 1980) and the current proposals for its revi- sion, which is referred to in this paper as ICIDH-2 (WHO, 1997). We will briefly review both of these conceptual frameworks. Both the Nagi Dis- ablement Model and the ICIDH frameworks have in common the view that overall disablement represents a series of related concepts that describe the consequences or impact of a health condition on a person’s body, on a person’s activities, and on the wider participation of that per- son in society. In the authors’ view, the major differences in these frame- works are in the terms used to describe disability and related concepts and the placement of the boundaries between concepts more than differ- ences in their fundamental contents. After reviewing the terms within each framework we will compare and contrast the two major models along with their major derivatives and explore how these relate more generally to the concept of “work disability.” Nagi’s Concept of Disability According to the conceptual framework of disability developed by sociologist Saad Nagi (1965), “disability is the expression of a physical or a mental limitation in a social context.” In striking contrast to the Social Secu- rity Act’s definition of work disability as an inability to work due to a physical or mental impairment, Nagi specifically views the concept of disability as representing the gap between a person’s capabilities and the demands created by the social and physical environments (Nagi, 1965, 1976, 1991). This is a fundamental distinction of critical importance to scholarly discussion and research related to disability phenomena. According to Nagi’s own words: [Disability is a] limitation in performing socially defined roles and tasks expected of an individual within a sociocultural and physical environ- ment. These roles and tasks are organized in spheres of life activities such as those of the family or other interpersonal relations; work, employment, and other economic pursuits; and education, recreation, and self-care. Not all impairments or functional limitations precipitate disability, and similar patterns of disability may result from different types of impairments and limitations in function. Furthermore, identical

186 THE DYNAMICS OF DISABILITY types of impairments and similar functional limitations may result in different patterns of disability. Several other factors contribute to shaping the dimensions and severity of disability. These include (a) the individ- ual’s definition of the situation and reactions, which at times compound the limitations; (b) the definition of the situation by others, and their reactions and expectations—especially those who are significant in the lives of the person with the disabling condition (e.g., family members, friends and associates, employers and co-workers, and organizations and professions that provide services and benefits); and (c) characteristics of the environment and the degree to which it is free from, or encum- bered with, physical and sociocultural barriers. (Nagi, 1991, p. 315) Nagi’s definition stipulates that a disability may or may not result from the interaction of an individual’s physical or mental limitations with the social and physical factors in the individual’s environment. Consis- tent with Nagi’s concept of disability, an individual’s physical and mental limitations would not invariably lead to work disability. Not all physical or mental conditions would precipitate a work disability, and similar patterns of work disability may result from different types of health con- ditions. Furthermore, identical physical and mental limitations may result in different patterns of work disability. Nagi’s Disablement Model has its origins in the early 1960s. As part of a study of decision making in the SSDI program, Nagi (1964) constructed a framework that differentiated disability (as defined and discussed above) from three other distinct yet interrelated concepts: active pathol- ogy, impairment, and functional limitation. This conceptual framework has come to be referred to as Nagi’s Disablement Model. For Nagi, active pathology involves the interruption of normal cellular processes and the simultaneous homeostatic efforts of the organism to regain a normal state. He notes that active pathology can result from infection, trauma, metabolic imbalance, degenerative disease processes, or other etiology. Examples of active pathology are the cellular distur- bances consistent with the onset of disease processes such as osteoarthritis, cardiomyopathy, and cerebrovascular accidents. For Nagi, impairment refers to a loss or abnormality at the tissue, organ, and body system level. Active pathology usually results in some type of impairment, but not all impairments are associated with active pathology (e.g., congenital loss or residual impairments resulting from trauma). Impairments can occur in the primary locale of the underlying pathology (e.g., muscle weakness around an osteoarthritic knee joint), but they may also occur in secondary locales (e.g., cardiopulmonary decondi- tioning secondary to inactivity). To describe the distinct consequences of pathology at the level of the

CONCEPTUAL ISSUES IN THE MEASUREMENT OF WORK DISABILITY 187 individual, Nagi uses the term functional limitations to represent restric- tions in the basic performance of the person. An example of basic func- tional limitations that might result from a cerebrovascular accident could include limitations in the performance of locomotor tasks, such as the person’s gait, and basic mobility, such as transfers, or in nonphysical tasks, such as communication or reasoning. Such functional limitations might or might not be related to specific impairments (secondary to the cerebrovascular accident) and thus are seen as distinct from organ or body system disturbances. At this point, a “work disability” example will illustrate the distinc- tions being drawn between the various concepts within Nagi’s Disable- ment Model. Two patients with Parkinson’s disease may enter the Social Security work disability benefits determination process with very similar clinical profiles. Both may have moderate impairments such as rigidity and bradykinesia. Their patterns of function may also be similar with a characteristically slow, shuffling gait, and slow deliberate movement pat- terns. Their work role patterns, however, may be radically different. One individual may have restricted his or her outside activities completely, need help dressing in the morning, spend most of the time indoors watch- ing television, be depressed, and be currently unemployed. The other may be fully engaged in his or her social life, receive assistance from a spouse in performing daily activities, be driven to work, and, through workplace modification, be able to maintain full-time employment. The two patients present very different work disability profiles yet have very similar underlying pathology, impairment, and functional limitation profiles. Elaboration of Nagi’s Disablement Model In their work on the disablement process, Verbrugge and Jette (1994) maintained the basic concepts of the Nagi Disablement Model and Nagi’s original definitions. Within the dimension of disability, however, they categorized subdimensions of social roles that can be considered under Nagi’s concept of disability. Some of the most commonly applied dimen- sions include the following: • Activities of daily living (ADL)—including behaviors such as basic mobility and personal care. • Instrumental activities of daily living (IADL)—including activities such as preparing meals, doing housework, managing finances, using the telephone, and shopping. • Paid and unpaid role activities—including performing one’s occupa- tion, parenting, grandparenting, and being a student.

188 THE DYNAMICS OF DISABILITY • Social activities—including attending church and other group activities and socializing with friends and relatives. • Leisure activities—including participating in sport and physical recreation, reading, or taking distant trips. Within their framework, “work disability” is clearly delineated as a specific subdimension under the concept of disability. In their 1994 work, Verbrugge and Jette attempted to extend Nagi’s Disablement Model to attain full sociomedical scope. They attempted to clearly differentiate the “main pathways” of the disablement process (i.e., Nagi’s original concepts) from factors hypothesized or known to influ- ence the ongoing process of disablement (Figure 1). Viewed from a social epidemiological perspective, Verbrugge and Jette (1994) argued that one might analyze differences in disablement concepts relative to three sets of variables: predisposing risk factors, intra- individual factors, and extraindividual factors. These categories of vari- ables, which are external to the main disablement pathway, can be defined as follows: • Risk factors are predisposing phenomena that are present before the onset of the disabling event and that can affect the presence or severity of the disablement process. Examples include socio- demographic background, lifestyle, and biological factors. • The next class of variables is intraindividual factors (those that operate within a person), such as lifestyle and behavioral changes, psycho- social attributes and coping skills, and activity accommodations made by the individual after the onset of a disabling condition. • Extraindividual factors (those that perform outside or external to the person) pertain to the physical as well as the social context in which the disablement process occurs. Environmental factors relate to the social as well as the physical environmental factors that bear on the disablement process. These can include medical and rehabilitation services, medications and other therapeutic regimens, external sup- ports available in the person’s social network, and the physical environment. A further elaboration of Nagi’s conceptual view of the term disability is contained in Disability in America (Pope and Tarlov, 1991) and a more recent Institute of Medicine (IOM) disablement model revision high- lighted in a report titled Enabling America: Assessing the Role of Rehabilita- tion Science and Engineering (Brandt and Pope, 1997). The 1991 report uses the original main disablement pathways put forth by Nagi with minor modifications of his original definitions. The

CONCEPTUAL ISSUES IN THE MEASUREMENT OF WORK DISABILITY 189 EXTRAINDIVIDUAL FACTORS: MEDICAL CARE AND REHABILITATION (surgery, physical therapy, speech therapy, counseling, health education, job retraining, etc.) MEDICATIONS AND OTHER THERAPEUTIC REGIMENS (drugs, recreational therapy/aquatic exercise, biofeedback/meditation, rest/energy conservation, etc.) EXTERNAL SUPPORTS (personal assistance, special equipment and devices, standby assistance/supervision, day care, respite care, meals-on-wheels, etc.) BUILT, PHYSICAL, AND SOCIAL ENVIRONMENTS (structural modifications at job/home, access to buildings and to public transportation, improvement of air quality, reduction of noise and glare, health insurance and access to medical care, laws and regulations, employment discrimination, etc.) THE MAIN PATHWAY FUNCTIONAL PATHOLOGY IMPAIRMENTS LIMITATIONS DISABILITY (diagnoses of (dysfunction and (restrictions in basic (difficulty doing activities of disease, injury, structural abnormalities physical and mental daily life: job, household congenital/ in specific body systems: actions: ambulate, management, personal care, developmental musculoskeletal, reach, stoop, climb hobbies, active recreation, condition) cardiovascular, stairs, produce clubs, socializing with neurological, etc.) intelligible speech, see friends and kin, child care, standard print, etc.) errands, sleep, trips, etc.) RISK FACTORS INTRAINDIVIDUAL FACTORS: (predisposing LIFESTYLE AND BEHAVIOR CHANGES characteristics: (overt changes to alter disease activity and demographic, social, impact) lifestyle, behavioral, psychological, PSYCHOSOCIAL ATTRIBUTES AND COPING environmental, (positive affect, emotional vigor, prayer, locus biological) of control, cognitive adaptation to one's situation, confidant, peer support groups, etc.) ACTIVITY ACCOMMODATIONS (changes in kinds of activities, procedures for doing them, frequency or length of time doing them) FIGURE 1 The disablement process (Verbrugge and Jette, 1994). Reprinted with permission from Elsevier Science.

190 THE DYNAMICS OF DISABILITY 1997 report adds two important concepts to the Disablement Model: the concepts of secondary conditions and quality of life. Both of these concepts are discussed later in this chapter. In 1997, in an effort to emphasize Nagi’s view that disability is not inherent in the individual (as defined by the Social Security Act), but, rather, is a product of the interaction of the individual with the environ- ment, IOM issued Enabling America, in which it referred to disablement as “the enabling-disabling process.” This effort was an explicit attempt to acknowledge, within the disablement framework itself, that disabling con- ditions not only develop and progress but can be reversed through the application of rehabilitation and other forms of explicit intervention. Figure 2 is an illustration of Brandt and Pope’s 1997 enabling-disabling process. The Brandt and Pope report (1997) describes the enabling-disabling process as follows: Access to the environment, depicted as a square, represents both physi- cal space and social structures (family, community, society). The per- son’s degree of physical access to and social integration into the general- ized environment is shown as the degree of overlap of the symbolic person and the environmental square. A person who does not manifest disability (Figure 2a) is fully integrated into society and has full access to both: (1) social opportunities (e.g., employment, education, parent- hood, leadership roles) and (2) physical space (e.g., housing, workplaces, transportation). A person with disabling conditions has increased needs (shown as the increased size of the individual) and is dislocated from their prior integration into the environment (Figure 2b). The enabling (or rehabilitative) process attempts to rectify this displacement, either by restoring function in the individual (Figure 2c) or by expanding access to the environment (Figure 2d) (e.g., building ramps). (Brandt and Pope, 1997, p. 3) International Classification of Impairments, Disabilities, and Handicaps Independently from the development of the Nagi model, a similar process was also underway in Europe, which led in the early 1970s to the first draft of what later became the World Health Organization (WHO) ICIDH (WHO, 1980). This model also differentiates a series of related concepts: health conditions, impairments, disabilities, and handicaps (WHO, 1980; Badley, 1993). We will refer to these as the ICIDH-1 con- cepts. ICIDH-1 is not only a conceptual model; it has also associated with it a hierarchical classification of impairment, disability, and handicap (WHO, 1980). We will not review this classification as such, except to note

Environmental Modification Ramps; universal The Environment design (physical and social) “Enlarge” the environment d to make it more accessible Disabling Process Enabling Person's needs Process enlarge relative to The “person” in the existing environment “environment” a b Functional Restoration Neural repair; Range of motion; Artificial hip replacement c Restore a person's functionality FIGURE 2 Conceptual overview of the enabling-disabling process. The environment, depicted as a square, represents both physical space and social structures (family, community, society). A person who does not manifest a disability (a) is fully integrated into society and “fits within the square.” A person with potentially disabling conditions has increased needs (ex- pressed by the size of the individual) and is dislocated from his or her prior integration into the environment (b), that is, “doesn’t fit in the square.” The enabling (or rehabilitative) process attempts to rectify this displacement, either by restoring function in the individual (c) or by expanding access to the environment (d) (e.g., building ramps) (Brandt and Pope, 1997). 191

192 THE DYNAMICS OF DISABILITY that, in principle, this system provides a scheme for coding and manipu- lating data on the consequences of health conditions. This classification and the related model of disablement are being revised and have been named ICIDH-2. At the time of this writing (April 1999), a first, beta draft has been circulated for comment (WHO, 1997), and the beta-2 draft is in the final stages of production. The beta-2 draft revised classification will then undergo 2 years of field testing before the final version is prepared for ratification by the WHO. The changes in the definitions and concep- tual model that are being recommended in the process of revision to get ICIDH-2 are discussed below. The U.S. National Center for Health Statis- tics and the Centers for Disease Control and Prevention have served as the lead U.S. agencies in the international ICIDH revision process. The first component of the ICIDH-1 model is impairment, which is defined as follows: In the context of health experience, an impairment is any loss or abnormality of psychological, physiological, or anatomical structure or function. (WHO, 1980, p. 27) This definition is similar to Nagi’s definition of impairment, but it also includes some of Nagi’s notions of pathology. Just as Nagi’s impair- ment is focused on organs or organ systems, impairment as defined here is very much concerned with the function and structure of the body and its components. The ICIDH-2 definition is similar: Impairment is a loss or abnormality of body structure or of a physiological or psychological function. (WHO, 1997, p. 15) Huge confusion arises because the ICIDH-1 also uses the word dis- ability, but with a slightly different meaning from the Nagi definition of the term. The ICIDH-1 defines disability as follows: In the context of health experience, a disability is any restriction or lack (resulting from an impairment) of ability to perform an activity in the man- ner or within the range considered normal for a human being. (WHO, 1980, p. 28) The focus of this definition is very much on the activities carried out by the person. Further understanding of what is included in this defini- tion can be gained by inspection of the associated classification (WHO, 1980, 1997). The activities included range from simple functional activi- ties, such as gripping and holding and maintaining and changing body positions, to more complex activities, such as those related to self-care

CONCEPTUAL ISSUES IN THE MEASUREMENT OF WORK DISABILITY 193 and other ADLs, IADLs, and some of the activity components of other role activities. The latter include, for example, activities that might be carried out in a work environment. Examples from the ICIDH-1 classifica- tion include activities such as organizing a daily routine (ICIDH 1980, Code D18.2), use of foot control mechanisms (ICIDH 1980, Code D67), and tolerance of work stress (ICIDH 1980, Code D76). The ICIDH-1 term disability then bridges the Nagi concepts of functional limitation and dis- ability. In revision of the ICIDH, the term disability has been replaced by the positive term activity, which is defined as follows: Activity is the nature and extent of functioning at the level of the person. Activities may be limited in nature, duration and quality. (WHO, 1997, p. 14) To prevent further confusion, the rest of this paper will use the term disability solely in the Nagi sense and use the term activity limitation for the ICIDH concept. In terms of definitions, the construct analogous to the Nagi definition of disability is embodied in the term handicap. This is defined as follows: In the context of health experience, a handicap is a disadvantage for a given individual, resulting from an impairment or a disability, that limits or pre- vents the fulfillment of a role that is normal (depending on age, sex, and social and cultural factors) for that individual. (WHO, 1980, p. 29) As is apparent from the definition, handicap, like Nagi’s disability, also embodies the notion of role. However, by referring to disadvantage it goes further than the actual performance of roles to attach a value judg- ment, that of disadvantage, to restrictions in role performance. The focus of handicap is the person in the society in which he or she lives and reflects cultural norms and expectations for performance. The term handicap did not generally find favor, particularly among people who themselves had disabilities, as it carried within it a history of stigmatization (unrelated to its technical definition). In the ICIDH revi- sion process, this questioning of the term handicap spilled over to the whole of the classification and led to the issue of why the emphasis was entirely on the negative. In other words there was a reaction against the whole classification being focused on deficiencies resulting from health conditions. In response to this there has been a switch to neutral terminol- ogy, as was illustrated above by the use of the term activity instead of the term disability. In the proposal for revision of the ICIDH, the concept of handicap, as defined above, has been replaced with the term participation, with negative aspects being referred to as restriction in participation:

194 THE DYNAMICS OF DISABILITY Participation is the nature and extent of a person’s involvement in life situations in relation to impairments, activities, health conditions and con- textual factors. Participation may be restricted in nature, duration and quality. (WHO, 1997, p. 14) Like Nagi’s definition of disability, the ICIDH definitions of handicap and participation are essentially relational concepts. This is made very explicit in the ICIDH-2, which states that: Participation is characterized as the outcome or result of a complex rela- tionship between, on the one hand, a person’s health condition, and in particular, the impairments or disabilities he or she may have, and on the other, features of the context that represent the circumstances in which the person lives and conducts his or her life . . . different environ- ments may have a different impact on the same person with impairment or disability. Participation is therefore based on an ecological/environ- mental interaction model. (WHO, 1997, p. 17) The conceptual model that accompanies the ICIDH-2 shows that the context potentially has an effect on the expression of all levels of the model: impairment, activity limitation, and restriction in participation. The context refers both to external environmental factors and to more personal characteristics of an individual. The latter range from relatively uncontroversial characteristics, such as age and gender, to aspects of the person relating to educational background, race, experiences, personality and character style, aptitudes, other health conditions, fitness, lifestyle, habits, coping styles, social background, profession, and past and current experience (WHO, 1997). ICIDH-2 includes a draft classification of envi- ronmental factors that covers components of the natural environment (weather or terrain), the human-made environment (tools, furnishings, the built environment), social attitudes, customs, rules, practices and in- stitutions, and other individuals (WHO, 1997). All of the above contextual factors may be relevant, in connection with the impairments or activity limitations of a person, for determining whether that person experiences disability in working or not. Finally, the ICIDH-2 concept of participation goes beyond the perfor- mance of roles and deals with the wider issues of the effect of barriers and facilitators to overall participation in society. In the context of work dis- ability these barriers and facilitators include discrimination, stigma, legis- lation around workplace design and participation (including the Ameri- cans with Disabilities Act), attitudes of coworkers, and extra-work issues such as mobility in the community. This means that an assessment of restriction of participation does not necessarily need to be on a personal basis and might, in some situations, be predicted by direct assessment of

CONCEPTUAL ISSUES IN THE MEASUREMENT OF WORK DISABILITY 195 barriers. For example, workplaces that are not accessible to wheelchair users would systematically restrict participation, irrespective of the nature and demands of the actual work tasks. CONCEPT OF SOCIAL ROLES To understand fully how Nagi’s definition of disability and the ICIDH definition of handicap can be applied to the area of work disability, one must understand the concept of social role and tasks from a sociological perspective. Social roles, such as being a parent, a construction worker, or a university professor, are basically organized according to how indi- viduals participate in a social system. According to Parsons (1958), “role is the organized system of partici- pation of an individual in a social system” (p. 316). Tasks are specific activities through which the individual carries out his or her social roles. Social roles are made up of many different tasks, which may be modifi- able and interchangeable. For Nagi, the concept of disability is firmly rooted in the context of health. Thus, for Nagi (1991), health-related limita- tions in the performance of specific social roles are what constitute spe- cific areas of disability, work being one important area of disability. Roles such as work can be disrupted by a variety of factors other than those that are health related. A change in the economic climate or technological changes, for example, may lead to unemployment totally unrelated to health conditions. These would not represent work disability in the way that Nagi defines this term. As Parsons clarifies: Roles, looked at that way, constitute the primary focus of the articula- tion and hence interpretation between personalities and social systems. Tasks on the other hand, are both more differentiated and more highly specified than roles, one role capable of being analyzed into a plurality of different tasks. . . . A task, then, may be regarded as that subsystem of role which is defined by a definite set of physical operations which per- form some function or functions in relation to a role. (Parsons, 1958, p. 316) Are there limits to this concept of disability from the perspective of role performance? Nagi argues that components of roles—expectations or specific tasks that are learned, organized, and purposeful patterns of be- havior—are part of the disability concept. They are more than isolated functions or muscle responses (Sarbin and Allen, 1968; Nagi, 1991). Some tasks are role specific, whereas others are common to the enactment of several roles. For Nagi, to the extent that these tasks are learned, orga- nized, and purposeful patterns of behavior, they are part of the disability concept. It is for this reason that Nagi views the concept of disability as ranging from very basic ADLs to the exquisitely complex social roles such

196 THE DYNAMICS OF DISABILITY as one’s occupation. Since activities of daily living (e.g., dressing, bathing, and eating) are part of a set of expectations inherent in a variety of other social roles, Nagi sees deviations or limitations in the performance of even such basic social roles as components of the concept of disability (Nagi, 1991). For Nagi, disability as a heuristic concept is inclusive of all socially defined roles and tasks. In the ICIDH-2, overall role performance mainly falls into the domain of participation. The boundary between activity limitation and participa- tion is drawn differently from the way in which it is drawn in the Nagi model, in that a person who is unable to perform activities that are the components of roles is considered to have activity limitations (Figure 3). These are the roles that Nagi refers to as “basic social roles.” In the context of work disability, the distinction is between restriction of participation related to work as an overall concept and the carrying out of the activities involved in the work itself. This is discussed in more detail in the section that explores conceptual issues related to work disability. Fundamental to differentiating the concept of disability from those of pathology, impairment, and functional limitation is the consideration of the difference between concepts of attributes or properties on the one hand and relational concepts on the other (Cohen, 1957). As Nagi describes it: Concepts of attributes and properties refer to the individual characteris- tics of an object or person, such as height, weight, or intelligence. Indica- tors of these concepts can all be found within the characteristics of the individual. Pathology, impairment, and functional limitations are con- cepts of attributes or properties. . . . Disability is a relational concept; its indicators include individuals’ capacities and limitations, in relation to role and task expectations, and the environmental conditions within which they are to be performed. (Nagi, 1991, p. 317) Let us take the example of limitation in the performance of one’s work role—or work disability. Work disability typically begins with the onset of one or more health conditions that may limit the individual’s performance of specific tasks through which an individual would typi- cally perform his or her job. The onset of a specific health condition—say, a stroke or a back injury—may or may not lead to actual limitation in performing the work role, a work disability. The development of work disability will depend, in part, on the extent to which the health condition limits the individual’s ability to perform specific tasks that are part of one’s occupation, and alternatively, degree of work disability may depend on external factors, for example, workplace attitudes—say, flexible work- ing hours—that may restrict employment opportunities for persons with specific health-related limitations. Or work disability might be affected by

Pathology (Nagi) Impairment Functional Disability (Nagi) Type of (Nagi) Limitation (Nagi) Impact Impairment Activity Limitation Participation Restriction (ICIDH-2) (ICIDH-2) (ICIDH-2) Interruption or Loss or Limitation in Inability or interference of abnormality of performance at the limitation in normal bodily mental, level of the whole performing processes or emotional, organism or socially defined structures physiological, roles and tasks or anatomical expected of structure or individuals within function* a social and Definition physical environment Loss or Restriction in the nature abnormality of Limitation in the and extent of the person's body structure or performance, involvement in life of a physiological accomplishment, or situations in relation to or psychological completion of an impairments, activities, function activity health conditions, and contextual factors Cells and tissues Organs and Organism—action Society—task organ systems or activity performance performance within the Level of (consistent with social and the purpose or cultural context Applicability function of the organ and organ Body (body parts) Person (as a whole) Society (relationships within society) FIGURE 3 Comparison of the Nagi and ICIDH-2 concepts and definitions. *Includes all losses and abnormalities, not just those attributable to active pathology; also includes pain. 197

198 THE DYNAMICS OF DISABILITY accessible modes of transportation to the workplace, environmental bar- riers in the workplace, or the willingness of the employer to modify the individual workstation to accommodate a health condition. Viewed from the perspective of role performance, degree of work disability could be reduced by improving the individual’s capacity to accomplish functional activities—a very traditional view of rehabilitation—or by manipulating the physical or social environment in which work occurs. A discussion similar to that given above could be formulated by using the language of the ICIDH. The fundamental conceptual issue of concern is that a health-related restriction in work participation may not be solely or even primarily related to the health condition itself or its severity. In other words, although the presence of a health condition is a prerequisite, “work disability” may be caused by factors external to the health condition’s impact on the struc- ture and functioning of a person’s body or the person’s accomplishment of a range of activities. DIRECTIONALITY AND THE DYNAMIC NATURE OF DISABILITY The earliest disablement models represented by the ICIDH-1 formula- tion (WHO, 1980) and Nagi’s disablement model (Nagi, 1965) presented the disablement process as more or less a simple linear progression of response to illness or consequence of disease. One consequence of this traditional view is that disabling conditions have been viewed as static entities (Marge, 1988). This traditional, early view of disablement failed to recognize that disablement is more often a dynamic process that can fluctuate in breadth and severity across the life course. It is anything but static or unidirectional. More recent disablement formulations or elaborations of earlier mod- els have explicitly acknowledged that the disablement process is far more complex (Pope and Tarlov, 1991; Verbrugge and Jette, 1994; Brandt and Pope, 1997; WHO, 1997; Fougeyrollas, 1998). These more recent authors all note that a given disablement process may lead to further downward- spiraling consequences. These feedback consequences, which may involve pathology, impairments, and further limitations in function or disability, have been explicitly incorporated into the graphic illustrations of more recent disablement formulations. The Pope and Tarlov (1991) report uses the term secondary conditions to describe any type of secondary conse- quence of a primary disabling condition. Commonly reported secondary conditions include pressure sores, contractures, depression, and urinary tract infections (Marge, 1988); but it should be understood that they can be either a pathology, an impairment, a functional limitation, or an addi- tional disability.

CONCEPTUAL ISSUES IN THE MEASUREMENT OF WORK DISABILITY 199 Longitudinal analytic techniques now exist to incorporate secondary conditions into research models and are beginning to be used in disable- ment epidemiological investigations (Lawrence and Jette, 1996). HOW DISABLEMENT CONCEPTS DIFFER FROM QUALITY OF LIFE AND SIMILAR CONCEPTS To compare disablement concepts with the phenomenon of quality of life, one must first consider how quality of life has been defined in the literature. Birren and Dieckermann have provided a useful starting point: The concept of quality of life is complex, and it embraces many charac- teristics of the social and physical environments as well as the health and internal states of individuals. There are two approaches to the mea- surement of quality of life: One is based upon the subjective or internal self perceptions of the quality of life; the other approach is objective and based upon external judgments of the quality of life. (Birren and Dieckermann, 1991, p. 350) If we apply Birren and Dieckermann’s perspective to work roles and work disability, objective dimensions of quality of life might include whether a person has had to change jobs because of a health problem, whereas the subjective dimension might include the individual’s satisfac- tion with his or her job. Consistent with this objective and subjective view of quality of life, Lawton (1983) has suggested that measures of quality of life should include a multidimensional evaluation of both intrapersonal and social-normative criteria including: 1. psychological well-being, 2. perceived quality of life, 3. behavioral competence in multiple areas (i.e., health, functional health, cognition, time use, and social behavior), and 4. the objective environment itself. Indicators of quality of life are extremely broad and have included standard of living, economic status, life satisfaction, quality of housing and the neighborhood in which one lives, self-esteem, and job satisfac- tion. Such a broad concept subsumes many dimensions of personal well- being not directly related to health. In response to concerns about the breadth of overall quality of life, some health researchers have adopted a narrower concept called “health- related quality of life.” Health-related quality of life has been defined in line with WHO’s definition of health as a state of complete physical, mental, and social well-being, not merely the absence of disease or infir-

200 THE DYNAMICS OF DISABILITY mity (WHO, 1947). Major dimensions in the health-related quality-of-life measures include signs and symptoms of disease, performance of basic physical activities of daily life, performance of social roles, emotional state, intellectual functioning, general satisfaction, and perceived well- being. Some models of disablement such as the IOM formulation (Pope and Tarlov, 1991; Brandt and Pope, 1997) and Patrick’s (1997) conceptual work clearly define quality of life as distinct from the disabling process. As Pope and Tarlov (1991) describe it: Quality of life affects and is affected by the outcomes of each stage of the disabling process. Within the disabling process, each stage interacts with an individual’s quality of life; it is not an endpoint of the model but rather an integral part. (p. 8) This view of quality of life strikes the authors as inconsistent with the definitions of quality of life described previously and may create prob- lems in designing appropriate survey measures. The concepts of quality of life and health-related quality of life, in particular, appear to overlap and include within their boundaries many (yet certainly not all) of the disablement concepts reviewed in this paper. Like the disablement con- cept, quality of life includes dimensions at the personal activity and social role levels. Like the disablement concepts, quality of life does direct some attention to the concepts of disease, through an assessment of signs and symptoms. Most quality-of-life measures focus little attention on organ and body system functioning and focus more on the consequences of impairments at the personal activity or social role level. At the level of social roles, quality-of-life dimensions are broader than the disablement concepts that incorporate overall life satisfaction, energy, vitality, and emotional well-being (Levine and Croog, 1984). Thus, the authors have difficulty viewing the concept of quality of life as entirely distinct from several dimensions in the disablement concepts. For some elements of quality of life, disablement is clearly a precursor, but other elements fall outside the disablement formulation. There ap- pears to be considerable overlap between elements of the two formula- tions, and a conceptualization that acknowledges this overlap may be a more useful formulation (Figure 4). CONCEPTUAL ISSUES RELATED TO THE MEASUREMENT OF WORK DISABILITY The underlying structure of models of disablement, as currently con- ceived, maps a pathway between the health condition and the ensuing

CONCEPTUAL ISSUES IN THE MEASUREMENT OF WORK DISABILITY 201 Quality of Life (e.g., emotional well-being, behavioral competence, sleep and rest, energy and vitality, general life satisfaction) Functional Disability/ Pathology Impairment limitation handicap Organ/Body System Level Personal/Social Level FIGURE 4 Relationship of disablement process to quality of life. “work disability” or other restrictions to social participation. Close in- spection of the definitions given above suggests that a number of steps can be identified in the pathway between the health condition and the social consequences described as work disability. At a micro level there are the pathological changes in the body and impairment in the structure and functioning of organs and body systems. There may be an impact on the activity of the person, ranging from simple movements, to basic ac- tivities of daily living, to instrumental activities of daily living, and so on. These can then contribute to the performance of more complex social roles, and ultimately, the person’s participation in all aspects of society can be adversely affected. Work is one such social role. Both the Nagi and the ICIDH models cover the spectrum of the conse- quences of health conditions. As indicated earlier, as well as terminology, a major difference is where these models place the boundaries between the different concepts (see Figure 3). In the Nagi model the performance of all activities, except for basic actions or functions of the body, is sub- sumed into the overall category of disability (Nagi, 1976). In the ICIDH model the concept of activity includes these basic actions as well as ADLs, IADLs, and some other role activities (with the emphasis very much on activity) (WHO, 1980, 1997; Badley, 1993). Participation is reserved to highlight the way in which the performance of activities may be con- strained by more than the immediate context of the activity. The juxtapo- sition of the two models in this way illuminates some nuances in the ways

202 THE DYNAMICS OF DISABILITY in which the impact of health conditions can been conceptualized as hav- ing an impact on the overall functioning of the individual. As indicated earlier, work disability is a function of whether the person can perform specific work-related tasks and of external factors. From the point of view of the measurement of work disability, it may be useful to distinguish between the degree of difficulty that a person may have in carrying out an activity and these other factors (such as barriers in the environment, atti- tudes of employers or coworkers, and other restrictions) that might pre- vent the performance of those activities in daily life. In this way, the levels of impact described within the conceptual models are of importance as they allow us to locate where many of the current types of assessment of work disability might fit in. In the authors’ view, in general, no explicit conceptual framework appears to be used in the ascertainment of work disability. A number of implicit conceptual approaches appear to have been used to assess and identify people with possible work disabilities. Each approach can be compared to the different levels of a model of disablement as discussed in the previous sections. We will review these in turn. However, before we do this we need to deal with some more general issues. Discrete or Continuous Phenomena Disability is commonly presented as an all-or-nothing phenomenon; either a person has a disability or a person does not. In reality, disability (in particular, roles or activities) is usually encountered in terms of degree of difficulty, limitation, or dependence, ranging from slight to severe. The question then becomes: where on the disability spectrum is that threshold that determines if a person is disabled? This needs to take into account any assistive devices or accommodations that the person may have. In the current context, work participation is often determined as being an end- point, in that either people have a work disability or they do not. In reality, the situation is likely to be more complex. For example, many people with functional and activity limitations may continue to work, but their labor force participation may be compromised in some way by the condition. To the extent that it is, these people might be said to have some degree of work disability. In measuring work disability, a clear definition of the threshold used needs to be made. Alternatively, a continuous mea- surement needs to be undertaken. Duration or Chronicity There is a pervasive assumption that work disability is long-term state. Stereotypes about disability are dominated by the archetype of a

CONCEPTUAL ISSUES IN THE MEASUREMENT OF WORK DISABILITY 203 person who uses a wheelchair. Embedded in this is the notion of some disabling event, a period of adjustment and rehabilitation, and then the resumption of as full a life as possible with the assistance of any necessary assistive devices or accommodations. With many impairments, the reality of disability is somewhat different. The majority of individuals in the working-age population with long-term activity restrictions report that this restriction is due to musculoskeletal, circulatory, or respiratory dis- orders (LaPlante and Carlson, 1996). These conditions may also be associ- ated with varying degrees of “illness,” so that it is not just an issue of physical performance. There are also considerations of pain, fatigue, and other symptoms. Many of these conditions are episodic in nature and may have trajectories of either deterioration or recovery (the latter being less common). This means that, apart from any environmental barriers or facilitators, the day-to-day or month-to-month experience of disability may be variable. This may need to be taken into account in any measure- ment scheme. Examples of Conceptual Approaches to Measuring Work Disability All disablement concepts appear to have been addressed, at least to some extent, as part of efforts to assess work disability. Health Condition or Pathology Under some circumstances knowledge of the health condition or pathology contributes to an assessment of work disability. Medical list- ings of diagnosis and medical severity have been used by some agencies to identify individuals who would be unlikely to benefit from vocational rehabilitation (Reno, 1999). Such listings have also been applied in the context of Social Security disability determinations. Concern has been expressed because the use of such listings might, on the one hand, deny benefits to individuals who need them and might, on the other, award benefits to those who could still work. Such concerns are a reflection of the many steps in the disablement model between the health condition and work disability. Impairment Assessments of work disability, or at least of entitlement to compen- sation for work injury, are often made at the level of impairment. The classic assessment is perhaps what has been pejoratively referred to as the “meat chart” assessment of the consequences of traumatic injury. An example of this would be the American Medical Association Guides to the

204 THE DYNAMICS OF DISABILITY Evaluation of Permanent Impairment (American Medical Association, 1993), which is a standardized system for translating the extent of an injury of a body part into a percentage of disability of the whole person. This type of system has been used for the assessment of compensation payments, including for workers’ compensation. A number of assessments focus on the functioning of the body, for example, assessments of strength, muscular endurance, body coordina- tion and flexibility, and cognitive and sensory functions (Fleishman, 1972, 1999). The problem with this impairment-focused approach is that even though these assessments may be made in the context of relating func- tional requirements with the requirements of certain jobs, one needs em- pirical evidence to support the contention that the degree of impairment is going to have a direct relationship to work disability. Without such evidence, the validity of such an approach is highly suspect. Functional Limitation Much of the discussion of assessment of work effectively has been at the level of functional disability. An example would be the assessment of abilities proposed for the Occupational Information Network (O*NET) system (see, for example, Wunderlich, 1999, p. 24). Here abilities such as oral comprehension, memorization, finger dexterity, and depth percep- tion (Wunderlich, 1999, p. 35) will be assessed and compared with the average requirements of particular jobs. Although the intent was that this should be done for all jobs, it has been suggested that this approach could, in principle, provide the basis of an assessment of work disability (Wunderlich, 1999, p. 86). Measures of work-related functional capacity (Lechner et al., 1997) have also been devised to test or ask about activities such as lifting, standing, walking, sitting, and carrying. Although closer in concept to work disability than assessments of pathology and impair- ment, assessments of capacity to perform work functions are one level removed from the concept of work disability. They look at the specific abilities of the individual for work in standardized ways not directly related to actual work settings. More importantly, they take no account of any environmental barriers or facilitators that might moderate the way in which a person’s functional limitations are expressed as disabilities. Activity Limitation (at Work) A direct way of answering at least part of the question about work disability is to carry out a workplace assessment. This gives information about whether the person can actually carry out the requirements for the major components of the job. This is the kind of assessment that is fre-

CONCEPTUAL ISSUES IN THE MEASUREMENT OF WORK DISABILITY 205 quently carried out in the context of vocational rehabilitation. However, factors other than the actual performance of the work tasks likely contrib- ute to work disability as indicated earlier. This is further discussed below. Work Disability Having separated out the activity limitation in work tasks, one can look at work disability from the perspective of carrying out a work role. Direct assessment of work disability involves several elements related to the role of work. These include: • activities within the workplace; • a range of other aspects including necessary mobility in getting to work; • interaction with colleagues, superiors, and subordinates; and • the amount and type of work that can be carried out. Work disability is most frequently assessed by direct inquiry of the individual. The measurement problems with this kind of approach are reviewed in Chapter 3. In population surveys the two main types of approaches to measurement of work disability are either (1) direct ques- tioning about any limitations in work attributable to a health condition or (2) the independent ascertainment of disability and work status, with some inference of a connection between disability and work status. We will review each of these in turn. DIRECT ASSESSMENT OF WORK DISABILITY The most direct approach to ascertainment of work disability is to inquire about working status together with questions as to whether non- participation is health related. There are various permutations on these types of questions. Some typical formulations are shown in Figure 5. As Figure 5 illustrates, typical survey questions about work disability are asked with a general reference to work, and it is left to the respondent to determine the specific relevant elements to be considered within the work role. If the respondent is currently working or has recently worked, this is presumably taken to mean the most recent working experience. If the person is not working, then this is more problematic. The answer to the question will depend on what type of employment, if any, the indi- vidual has in mind when answering the question. If the purpose of the question is to determine incapacity for work, then the nature of the job and any accommodations that have been or might be made is crucial. Few

206 THE DYNAMICS OF DISABILITY 1990 Decennial Census: Work Disability Does this person have a physical, mental or other health condition that lasted for 6 months or more which (a) limits the kind or amount of work this person can do at a job? (b) prevents this person from working at a job? U.S. Census for Year 2000 General question about activity limitations (difficulty in carrying out specific activities) because of a physical, mental, or emotional condition lasting 6 months or more. March Current Population Surveys, 1981–1988 The CPS has a set of criteria. If one or more of the final four conditions was met, the person was considered to have a severe work disability: 1. Does anyone in the household have a health problem or disability which prevents them from working or which limits the kind or amount of work they can do? Is there anyone in this household: 2. Who ever retired or left a job for health reasons? 3. Did not work in the survey week because of a long-term physical or mental illness or disability which prevents the performance of any kind of work? 4. Did not work at all in the previous year because ill or disabled? 5. Under 65 years of age and covered by Medicare? 6. Under 65 years of age and a recipient of Supplemental Security Income (SSI)? Survey of Income and Program Participation (Third Wave Supplement), 1984 Does ______’s health or condition limit the kind or amount of work _____ can do? National Health Interview Surveys Phase 1 a. Does ____’s health now keep him from working? b. Is he limited in the kind of work he could do because of his health? c. Is he limited in the amount of work he could do because of his health? d. Is he limited in the kind or amount of other activities because of his health? Phase 2 a. Does ____ now have a job? b. In terms of health is ____ now able to work? c. Is he limited in the kind of work he could do because of his health? d. Is he limited in the amount of work he could do because of his health? e. Is he limited in the kind or amount of other activities because of his health? FIGURE 5 Examples of survey questions.

CONCEPTUAL ISSUES IN THE MEASUREMENT OF WORK DISABILITY 207 survey research approaches break down work role into its major compo- nent parts to determine the perceived degree of disability within each. Typical survey research questions also leave it to the respondent to attribute not working to an underlying health condition. It may be that the individual answers that he or she cannot work, yet the person may not be given the opportunity to specify the circumstances under which this might be possible. A survey of working-age people with disability in the United States showed that over two-thirds wanted to work (Stoddard et al., 1988, p. 24). In the 1991 Canadian Health and Activity Limitation Survey, 64 percent of respondents with disabilities reported that they were not in the labor force, and over two-thirds of these said that they were completely prevented from working (Statistics Canada, 1993). How- ever, all respondents were given the opportunity to answer questions about needed accommodations in the workplace. Despite reporting that they were prevented from working, 69 percent of these individuals reported needing a variety of workplace accommodations (such as job redesign or modified hours) and 76 percent reported needing adaptations (such has handrails, elevators, or modified workstations). Whether or not the provision of such accommodations or adaptations would facilitate workplace reintegration is unknown. However, the findings illustrate how changing the framing of a question sheds a different light on what it means to be unable to work. Individuals who were not in the labor force were also asked about barriers to employment. The most frequently men- tioned barriers were losing some or all of their current income, feelings that their training was not adequate, no available jobs, and loss of addi- tional supports (such as health benefits). Other less frequently mentioned reasons were family responsibilities, having being the victim of discrimi- nation, and not having accessible transportation (Statistics Canada, 1993). In other words, most of the reasons were related not to the nature of the work, but to some of the other circumstances surrounding the issue of work disability. Furthermore, some individuals will have a choice as to how they describe their working status. For example, a person with a disability who also has small children could variously describe him- or herself as a home- maker or not being in the labor force because of the disability. Or people leaving the workforce in their 50s may describe themselves as having taken an early retirement. Without extra information it may be difficult to tell whether this is indeed the situation or whether the alternative description was seen as a less stigmatizing alternative to describing them- selves as having a work disability. In a survey research situation, if a person is working, the typical approach is to assume that no work disability is present. Nevertheless, the person may be limited in the amount or kind of work done or both.

208 THE DYNAMICS OF DISABILITY The person may be spending less time working, working at a less skilled job, or earning less money. This information can be obtained from survey questions (see Figure 5), but often with relatively little qualifications as to what this means. What is less often addressed is that for many people with disabilities working may mean forgoing opportunities to participate in other areas of life. Just going to work may, for example, exhaust all reserves of energy or require time-consuming preparations. There is a fine line between what might be considered a satisfactory accommoda- tion and an unsatisfactory compromise or necessity, and different people will value this trade-off differently. CONCLUSION The problem with all the approaches to work disability, as indicated by our discussion of conceptual frameworks, is that there is unlikely to be a one-to-one relationship between the presence of health conditions, im- pairments, functional limitations, or activity restrictions and disability in employment. There is a pervasive assumption that work disability relates to the person’s degree of functional limitation and activity restriction. This is reflected in the concern about assessment, where the focus is very much on the individual’s performance. Lip service is paid to the environ- ment, particularly in the context of work disability and vocational reha- bilitation. As we have tried to show, a full understanding of work disabil- ity needs to take into account the individual’s circumstances and the social and physical environments of the workplace. The research challenge is to apply the insights provided by the mod- els of disablement to come to a common understanding of work disability and to understand the relationships and the dynamics of the pathway between health conditions and work disability. Researchers need to find ways to incorporate an understanding of the external factors that influ- ence the development of work disability into its measurements. REFERENCES American Medical Association. 1993. Guides to the Evaluation of Permanent Impairment. 4th ed. Chicago: American Medical Association. Badley EM. 1993. An introduction to the concepts and classifications of the International Classification of Impairments, Disabilities, and Handicaps. Disability and Rehabilitation 15:161–178. Badley EM. 1995. The genesis of handicap: definitions, models of disablement, and role of external factors. Disability and Rehabilitation 17:53–62. Birren J, Dieckermann L. 1991. Concepts and content of quality of life in the later years: an overview. In: Birren J, et al., eds. Quality of Life in the Frail Elderly. New York, NY, Academic Press, Inc. Pp. 344–360.

CONCEPTUAL ISSUES IN THE MEASUREMENT OF WORK DISABILITY 209 Brandt E, Pope A, eds. 1997. Enabling America: Assessing the Role of Rehabilitation Science and Engineering. Washington, DC: National Academy Press. Cohen MA. 1957. Preface to Logic. New York: Meridian Books. Fleishman EA. 1972. Structure and measurement of psychomotor abilities. In: Singer RN, ed. The Psychomotor Domain: Movement Behavior. Philadelphia: Lea and Febiger. Fleishman EA. 1999. Linking components of functional capacity domains with work re- quirements. In: Wunderlich GS, ed. Measuring Functional Capacity and Work Require- ments: Summary of a Workshop. Washington DC: National Academy Press. Fougeyrollas P, ed. 1998. ICIDH and Environmental Factors International Network.Volume 9, Numbers 2–3. Quebec, Canada: Canadian Society for the ICIDH. Jette A, Assmann S, Rooks D, Harris B, Crawford S. 1998. Interrelationships among disable- ment concepts. J of Gerontol: Med Sci 53A(5):M395–M404. LaPlante MP, Carlson D. 1996. Disability in the United States: Prevalence and Causes, 1992. Disability Statistics. Report 7. Washington, DC: U.S. Department of Education, National Institutes on Disability and Rehabilitation Research. Lawrence R, Jette A. 1996. Disentangling the disablement process. Journal of Gerontol Soc. Sciences 51B(4):S173–S182. Lawton MP. 1983. Environment and other determinants of well being in older people. Ger- ontologist 23:349–357. Lechner, D, Roth D, Straaton K. 1997. Functional capacity evaluation in work disability. Work 1:31–47. Levine S, Croog S. 1984. What constitutes quality of life? A conceptualization of the dimen- sions of life quality in healthy populations and patients with cardiovascular disease. In: Wenger N, et al., eds. Assessment of Quality of Life in Clinical Trials of Cardiovascular Therapies. New York, NY: LeJacq Publ. Co. Pp. 46–66. Marge M. 1988. Health promotion for people with disabilities: Moving beyond rehabilita- tion. AM J Health Promotion 2(4):29–44. Mathiowetz N. 2000. Methodological issues in the measurement of work disability. In: Mathiowetz N, Wunderlich, GS, eds. Survey Measurement of Work Disability: Summary of a Workshop. Washington, DC: National Academy Press. Pp. 28–52. Nagi S. 1964. A study in the evaluation of disability and rehabilitation potential: Concepts, methods, and procedures. American Journal of Public Health 54:1568–1579. Nagi S. 1965. Some conceptual issues in disability and rehabilitation. In: Sociology and Reha- bilitation. Sussman MB, ed. Washington, DC: American Sociological Association. Nagi S. 1976. An epidemiology of disability among adults in the United States. In: Health & Society. Milbank Memorial Fund Quarterly 54:439–467. Nagi S. 1991. Disability concepts revisited: Implications for prevention. In: Pope A, Tarlov A, eds. Disability in America: Toward a National Agenda for Prevention. Washington, DC: National Academy Press. Parsons T. 1958. Definitions of health and illness in the light of American values and social structure. In: Jaco EG, ed. Patients, Physicians, and Illness. Glencoe, Ill: Free Press. Patrick DL. 1997. Rethinking prevention for people with disabilities: A conceptual model for promoting health. American Journal of Health Promotion 11(4):257–260. Pope A, Tarlov A, eds. 1991. Disability in America: Toward a National Agenda for Prevention. Washington, DC: National Academy Press. Reno V. 1999. Adapting measurement of functional capacity to work to SSA’s disability decision process. In Wunderlich GS, ed. Measuring Functional Capacity and Work Re- quirements. Summary of a Workshop. Washington, DC: National Academy Press. Pp. 74– 78 Sarbin T, Allen V. 1968. Role theory. In: Linsey G, Aronson E, eds. The Handbook of Social Psychology, Vol. 1, 2nd edition. Reading MA: Addison-Wesley Publ. Co.

210 THE DYNAMICS OF DISABILITY Statistics Canada. 1993. Adults with disabilities: Their employment and education charac- teristics. 1991 Health and Activity Limitation Survey. Ottawa: Statistics Canada Cata- logue 82–554. Stoddard S, Jans L, Ripple J, Kraus L. 1998. Chartbook on Work and Disability in the United States, 1998. An InfoUse Report. Washington, DC: U.S. National Institute on Disability and Rehabilitation Research. Verbrugge L, Jette A. 1994. The disablement process. Soc Sci & Med. 38(1):1–14. World Health Organization (WHO). 1947. Constitution of the World Health Organization. New York, NY: WHO. WHO. 1980. The International Classification of Impairments, Disabilities, and Handicaps—A Manual Relating to the Consequences of Disease. Geneva: WHO. WHO. 1997. ICIDH-2: International Classification of Impairments, Activities, and Participation. A Manual of Dimensions of Disablement and Functioning. Beta-1 Draft for Field Trials. Geneva: WHO. Wunderlich GS, ed. 1999. Measuring Functional Capacity and Work Requirements. Washington, DC: National Academy Press.

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The Society Security disability program faces urgent challenges: more people receiving benefits than ever before, the prospect of even more claimants as baby boomers age, changing attitudes culminating in the Americans With Disabilities Act. Disability is now understood as a dynamic process, and Social Security must comprehend that process to plan adequately for the times ahead. The Dynamics of Disability provides expert analysis and recommendations in key areas:

  • Understanding the current social, economic, and physical environmental factors in determining eligibility for disability benefits.
  • Developing and implementing a monitoring system to measure and track trends in work disability.
  • Improving the process for making decisions on disability claims.
  • Building Social Security's capacity for conducting needed research.

This book provides a wealth of detail on the workings of the Social Security disability program, recent and emerging disability trends, issues and previous experience in researching disability, and more. It will be of primary interest to federal policy makers, the Congress, and researchers—and it will be useful to state disability officials, medical and rehabilitation professionals, and the disability community.

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