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The Second Fifty Years: Promoting Health and Preventing Disability 2 Disability Classification Although disabilities have been the subject of health care research and services for many years, the field remains in conceptual disarray. Even today, health professionals share neither a common means of defining disabilities nor a common sense of the health care industry's role with regard to people with disabilities. This chapter addresses some of the difficulties and trade-offs involved in selecting a disability classification system to solve these problems and explains the committee's reasons for advocating the World Health Organization's International Classification of Impairments, Disabilities, and Handicaps.18 Why pursue a new means of classifying disability? Issues of disability classification have often revolved around the politically sensitive task of deciding whether particular individuals are eligible for social insurance programs, a process that in many circumstances provokes significant controversy. Many health professionals have, therefore, attempted to avoid these controversies by avoiding disability.7 With the prospect of providing care for an ever-larger aging population, however, the problems of disability classification deserve fresh attention. Older people are more likely to experience chronic illness that, over time, may contribute to disability, and the current lack of organization of disability concepts may leave American health care unprepared to deal with the growing future needs of this population. The committee's efforts, therefore, have been directed toward the identification of a disability classification system that offers a framework
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The Second Fifty Years: Promoting Health and Preventing Disability sensitive to the long-term needs of people with disabilities and that is likely to lead to a more unified understanding of these concepts among health professionals. Even without many of the political pressures that accompany efforts to certify individuals for government benefits, the task of disability classification remains deeply complicated. There are major incompatibilities between the thinking that currently dominates American health care and the service needs of people with disabilities. The following sections give an account of these difficulties, discuss the current state of affairs in disability classification and its effects on disability research, and explain the committee's decision to advocate the World Health Organization's system. DISABILITY AND THE DISEASE MODEL The dominant framework for understanding the majority of health problems in the United States is that of the acute care community, that is, the disease model. Yet more and more health professionals are beginning to question the wisdom of using this approach to meet the needs of people with disabilities and those at risk for disability2,8,19—in particular, the elderly, the fastest growing group at high risk for disabilities.16,17 An acute care framework provides a poor view of disability for a number of reasons. Acute care perspectives are primarily restricted to somatic conditions, yet contemporary concepts of disability include phenomena that go well beyond this sphere. Disability may limit an individual's capacity to live independently or care for him- or herself; it may interfere with maintaining or initiating relationships, pursuing career goals, or enjoying leisure activities. Disability may also erect barriers to personal autonomy (e.g., the inaccessibility of public accommodations) and political empowerment (e.g., through prejudice or discrimination) in American culture. The acute care perspective on health is also problematic for understanding and meeting the needs of people with disabilities and those who are at risk for disability. In the acute care framework, health is most often associated with cure, a linkage that is too limiting in the disability arena. (Some of the problems inherent in the health-equals-cure perspective are apparent when one considers that there is a cure for tuberculosis but no counterpart in treatments for missing or dysfunctional legs.) Health care that reduces its ultimate goal to that of the strictly curative is also likely to make the implicit assumption that health and the absence of disease are essentially synonymous. This assumption makes room for primary
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The Second Fifty Years: Promoting Health and Preventing Disability prevention, but it neglects the prevention of disabilities after a disease has been cured or measures to address the needs of individuals with chronic conditions. Moving from the level of organ or cell function to a consideration of the social effects of disability exposes further incompatibilities between disease-centered thinking and broad notions of disablement. The effects of disease are located in well-defined spaces—the organs and tissues of the human body. By contrast, the spaces disabilities affect are not well defined. Unlike human organs, an individual's life in society cannot be neatly divided into separate parts or components; when such divisions are attempted, the enormous variety of human existence guarantees small likelihood of consensus regarding either the divisions themselves or what constitutes ''normal functioning" within them. These incompatibilities are evident in the structure of acute care thinking. Each disease constitutes a paradigmatic set of signs and symptoms. Medical diagnosis is the categorical assignment of the patient's concrete and particular health problems to one or several universal disease types. Diagnosis therefore incorporates a shift in which a particular individual's sickness is assimilated into an established and consistent category that is (often) recognized universally within the health care system and associated with specific methods of treatment. Disease classification systems are designed to classify concepts that remain static and abstract.4 By contrast, the social manifestations of disabilities must be understood relative to the particular abilities an individual hopes to maintain or achieve. These abilities vary among individuals—they are often matters of individual preference, culture, and social expectations. Attempts to "diagnose" disability according to easily recognized physical abnormalities or by general standards of behavior and social performance may cause the personal aspects of disablement to be overlooked. For example, is it right—or, more important, will the necessary kind of care be delivered—if two wheelchair-bound individuals are classified as having the same disability if one is a mason and the other a writer? In this case, an apparently similar problem assumes quite different proportions and dimensions. Thus, social life not only resists well-defined divisions, but the uniqueness of an individual life makes it highly resistant to universal and abstract categories, which are an essential part of the logic of modern clinical methods. (It should be noted that the uncategorical nature of disabilities is not simply a problem for acute care thinking but for any and all methods that attempt to box a disabled person's difficulties into predetermined categories of ill health.)
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The Second Fifty Years: Promoting Health and Preventing Disability Despite these complications, there have been continuing attempts to define universal and abstract standards for describing and treating disabilities. Although these systems are often criticized for being inequitable, unjust, and inadequate, they serve a necessary purpose. The health care system in this country has been built on the understanding that illnesses can be categorized and are likely to follow a predictable course. These systems, therefore, provide the structure essential to integrate disabilities into the U.S. social insurance and health care systems. This means that the imperative is to find a system suited to the nation's needs but to remain sensitive to its inherent problems and open-minded about alternatives. The alternative to the acute care approach to disabilities explored in this report is the array of new methods and goals known as health promotion and disability prevention. This new approach makes room for broader notions of disability care and treatment, departing from the traditional disease model framework. Healthy behavior and the prevention of chronic and acute conditions through risk reduction are stressed, as in health promotion and disease prevention. However, in this approach, prevention is more comprehensive; that is, points of prevention for chronic illness and disability are defined throughout life, including periods after the onset of these difficulties. Rehabilitation and social supports tailored to the diverse needs of the over-50 population are also an important part of health promotion and disability prevention. Although the health promotion and disability prevention approach escapes many of the constraints of traditional acute care frameworks, the majority of its services are not delivered independently of existing health care systems. It therefore requires a common set of definitions, shared concepts to guide health policies and permit the dialogue necessary to advance disability treatment and prevention among health care providers. The following section discusses two of the recent efforts to classify disabilities and presents the committee's recommendations for the future development of this field. CLASSIFYING DISABILITIES As noted above, defining standards for disability in its broader manifestations is exceedingly difficult. There have been numerous attempts to devise disability classification systems in the United States, in part because of the rise of social insurance programs such as workmen's compensation, veterans' benefits, and social security programs.7,10 Another important source of disability classifications has been health interview surveys. From the time of their introduction
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The Second Fifty Years: Promoting Health and Preventing Disability to the United States, these surveys have grown increasingly sophisticated, and by the 1950s Katz and Lawton had developed short sets of survey questions based on behavioral theories of human function. These indexes are known as the Activities of Daily Living (ADLs), which measure abilities in six functions (bathing, dressing, toileting, transfer, continence, and feeding), and the Instrumental Activities of Daily Living (IADLs), which are concerned with more complex tasks (e.g., shopping, cooking, housekeeping, laundry, use of transportation, managing money, managing medications, use of telephones).9 Another measure, limitations in major activities, asks respondents about their ability to work, attend school, or perform housework.5 (A list of many of the major surveys, including those with questions on disability, can be found in the National Research Council publication, The Aging Population in the Twenty-first Century: Statistics for Health Policy .15) Each of these measures has been widely used—or retooled for use—in surveys and functional assessment inventories. Despite their widespread use, however, each of the classification systems that have come into use in this country suffers from limitations of one kind or another. From a research perspective, the use of self-reported measures raises questions concerning the standardization of the participant's answers. Disability measures have also been problematic as public policy-making tools. The eligibility criteria of the nation's social security insurance programs have been criticized for relying on the narrowly defined criteria of the disease model to determine disability.7,10 In health policy, the ADLs and IADLs have similar constraints. Although not dependent on the disease model, they do not have a systematic means of defining psychological difficulties, and they do not provide insight into certain social contributions to disability, such as discrimination. The systems measuring limitations in major activities, on the other hand, may indicate the presence of some social contributions to disability but do not provide sufficient information to inform health interventions. These limitations have been recognized and other forms of classification, including attempts to combine these measures, have been attempted, but there has been no consensus on a system that could provide a sufficiently broad understanding of disability. These and other specific measures provide insights into the way disabilities affect important parts of most people's lives, but their scope is too narrow. Moreover, health care measures are now called on to assess the quality of life, but without a fuller perspective on the effects of disability, such classification and measurement systems do not have a convincing claim to make such assessments.
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The Second Fifty Years: Promoting Health and Preventing Disability In the search for solutions, epidemiologists, demographers, physicians, insurers, and other health-related professionals have looked to classification systems that attempt to provide a comprehensive framework for understanding and acting on both the physical and social dimensions of disabilities. Several attempts have been made to classify a broad range of disability phenomena into categories organized according to various "levels," from the pathological to the individual to the social, on which disabling conditions exist. The World Health Organization's18 (WHO) International Classification of Impairments, Disabilities, and Handicaps (ICIDH) and the Nagi system11,12,13,14 are widely used and frequently discussed examples of this type of system. They both address somatic, cognitive, economic, and psychosocial dynamics; however, although they share common names for some of their categories, the criteria for determining category boundaries differ. The Nagi system is intended to provide general categories and a common conceptual model of disability processes for use in the multidisciplinary setting of disability research. The system draws a careful framework for understanding disabilities built around four basic concepts: pathology, impairment, functional limitation, and disability. The subdivisions for these concepts are, in part, based on concepts introduced previously by other systems for classification and assessment. The Nagi system is designed to correspond to the findings of empirical research. The demarcations between categories are said to mirror a set of "natural" divisions* suggested by survey research. For example, categories to identify the severity of functional limitations in "physical performance" and "emotional performance'' (two subcategories of the more general functional limitation category) were determined by analyzing survey data that indicated natural clusterings of individuals with similar severity scores.12,13 These and other strict epistemological standards limit the number of categories in the system. It therefore remains at a more abstract and less inclusive level of organization, eschewing highly detailed categories that may not fit neatly into the overall structure of the system or that are not backed by empirical evidence.14 By contrast, the organization of the WHO system reflects a desire to change * Nagi distinguishes the "natural" approach from more artificial methods that might, for example, have divided a 0-8 rating scale into such categories as 0-1.9, 2.0-3.9, and so forth, or that might set the boundaries of categories so as to achieve an equal distribution of individuals between them, rather than making divisions on the basis of clusters of individuals.13
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The Second Fifty Years: Promoting Health and Preventing Disability Classification Level Disease (or injuries or congenital abnormality) Impairment Disability Handicap Planes of Experience Exteriorized Objectified Socialized →General Progression of the Consequences of Disease→ Example: Osteoporosis with hip fracture Hip impairment Climbing staircases, steps, walking Mobility and independence handicaps FIGURE 2-1 The World Health Organization's International Classification of Impairments, Disabilities, and Handicaps. the landscape of health services by introducing measures of disability designed to direct system users to new health care goals. The WHO system categorizes a wide range of disease consequences and suggests points of intervention (to prevent further development) and forms of assistance to help individuals cope with their difficulties. The form and organization of the system are similar to WHO's International Classification of Diseases (ICD-9) especially in many of its subcategories; the overall structure, however, is informed by a theory of "planes of experience" in the development of illness and disability. This gives rise to four main categories: disease/disorder, impairment, disability, and handicap (Figure 2-1). The WHO manual describes these planes of experience (pp. 24-25) as follows:18 Something abnormal occurs within the individual; this may be present at birth or acquired later. A chain of causal circumstances, the "etiology," gives rise to changes in the structure or functioning of the body, the "pathology." Pathological changes may or may not make themselves evident; when they do they are described as "manifestations,'' which, in medical parlance, are usually distinguished as "symptoms and signs." These features are the components of the medical model of disease. Someone becomes aware of such an occurrence; in other words, the pathological state is exteriorized. Most often the individual himself becomes aware of disease manifestations, usually referred to as "clinical disease." In behavioral terms, the individual has become or been made aware that he is unhealthy. His illness heralds
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The Second Fifty Years: Promoting Health and Preventing Disability recognition of impairments, abnormalities of body structure and appearance, and of organ or system function, resulting from any cause. Impairments represent disturbances at the organ level. The performance or behavior of the individual may be altered as a result of this awareness, either consequentially or cognitively. Common activities may become restricted, and in this way the experience is objectified. Also relevant are psychological responses to the presence of disease, part of so-called illness behavior, and sickness phenomena, the patterning of illness manifested as behavior by the individual in response to the expectations others have of him when he is ill. These experiences represent disabilities, which reflect the consequences of impairments in terms of functional performance and activity by the individual. Disabilities represent disturbances at the level of the person. Either the awareness itself, or the altered behavior or performance to which this gives rise, may place the individual at a disadvantage relative to others, thus socializing the experience. This plane reflects the response of society to the individual's experience, be this expressed in attitudes, such as the engendering of stigma, or in behavior, which may include specific instruments such as legislation. These experiences represent handicap, the disadvantages resulting from impairment and disability. The explicit concern with the value attached to an individual's performance or status obviously makes this the most problematical plane of the disease consequences. Because the WHO system was designed as a classification manual for the consequences of disease, it does not elaborate the particular conditions that fall under the disease/disorder level. Impairments, the first WHO level with detailed subcategories, include "any loss or abnormality of psychological, physiological, or anatomical structure or function." As noted in the description above, these changes occur, in principle, at an organ level and begin with the development of pathological processes (although the impairment may outlast the pathological activity or may be of genetic origin). The next level, disabilities, describes restrictions or inabilities measured against social expectations of what "normal" humans can perform in managing the "essential components of everyday living" (e.g. personal care, locomotor activities, behaviors commonly expected of individuals). The last category in the WHO system is handicaps, which are disadvantages for a given individual, resulting from an impairment or disability, that limit or prevent "the fulfillment of a role that is normal for that individual." The handicap level is used to assess the impact of an impairment or disability in relation to the roles chosen
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The Second Fifty Years: Promoting Health and Preventing Disability by an individual and the social expectations that accompany that role. The assessment criteria of this level, however, are largely limited to "survival roles," or "six key dimensions of experience in which competence is expected of an individual": orientation, physical independence, mobility, occupation, social integration, and economic self-sufficiency. The potential effects of osteoporosis provide a convenient example of the WHO classification system (see Figure 2-1). Any resulting mechanical or motor dysfunction, for example, as a consequence of fracture would be classified as an impairment. The system provides detailed subcategories specifying functional limitations of particular limbs and major skeletal components such as hip and thigh impairments. Resulting difficulties in walking on flat terrain, traversing discontinuities (e.g., occasional steps between levels or the gap between platform and train), or climbing staircases are separate subcategories under the disabilities classification level. General mobility limitations or the resulting diminution of physical independence are classified as handicaps. The system provides general guidelines for assessing their severity. More widespread use of the WHO classification system offers several advantages, although like any such system it is not perfect. There is an urgent need to bring the concepts of disability and its prevention to the attention of physicians, and the familiar form of the WHO system is a suitable mechanism for their introduction. The system also provides a highly comprehensive perspective on disabling consequences of disease and the available interventions. It also holds promise as a means of achieving a common vocabulary for research and the systematic organization of concepts to facilitate data collection and assessment. In addition, the WHO system has already begun to achieve worldwide acceptance. Although some of the subcategories assert an order of disability phenomena that is neither empirically corroborated nor intuitively obvious, this disadvantage will be outweighed if the system encourages large numbers of health professionals to adopt this format as a regular means of recording data on disabilities. Much of the appeal of the WHO classification system lies in the new health care goals made explicit in its subcategories. It is in this context that the Committee on Health Promotion and Disability Prevention for the Second Fifty encourages physicians to shift their attention—and with it their frame of reference—toward providing comprehensive help for their elderly disabled patients. As a first step toward this goal the committee supports the use of the WHO system, the International Classification of Impairments, Disabilities, and
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The Second Fifty Years: Promoting Health and Preventing Disability Handicaps, as a descriptive framework for the disabling conditions associated with risk factors for older populations, including the conditions discussed in the remaining chapters of this report. The committee notes that health care for older individuals is currently in transition. Thus, methods that appear relevant and useful today may become outmoded as the discussion of disability classification continues. It is the committee's hope that widespread use of the WHO system will bring health professionals into this arena to contribute their views and insights to the development of alternative approaches. The committee also urges careful attention to the views of members of the disabled community, as well as bioethicists (see Appendixes A and B of this report), whose unique perspectives often reveal overlooked distinctions between disability in the abstract and in the "real" world. REFERENCES 1. Berkowitz, E., and D. Fox. The politics of social security expansion: Social security disability insurance, 1935–1986. Journal of Policy History 1989; 1(3):233-260. 2. Caplan, A. L. Is medical care the right prescription for chronic illness? In: S. Sullivan and M. E. Lewin (eds.), The Economics and Ethics of Long-Term Care and Disability. Lanham, Md.: University Press of America, 1988, pp. 73-89. 3. Engelhardt, H. T. The concepts of health and disease. In: A. L. Caplan, H. T. Engelhardt, and J. J. McCartney (eds.), Concepts of Health and Disease. Reading, Mass.: Addison-Wesley, 1981, pp. 31-45. 4. Foucault, M. The Birth of the Clinic, A. M. S. Smith, trans. New York: Random House, 1973. 5. Haber, L. D. Issues in the Definition of Disability and the Use of Disability Survey Data. Presentation at the Workshop on Disability Statistics of the Committee on National Statistics, National Research Council, Washington, D.C., 1989. 6. Institute of Medicine. National Agenda for the Prevention of Disability. Washington, D.C.: National Academy Press, forthcoming. 7. Institute of Medicine. Pain and Disability: Clinical, Behavioral, and Public Policy Perspectives. M. Osterweis, A. Kleinman, and D. Mechanic (eds.), Washington, D.C.: National Academy Press, 1987. 8. Jennings, B., D. Callahan, and A. L. Caplan. Ethical challenges of chronic illness. Hastings Center Report 1988; 2(Suppl.):1-16. 9. Katz, S. Assessing self-maintenance: Activities of daily living, mobility, and instrumental activities of daily living. Journal of the American Geriatrics Society 1983; 31(12):721-727. 10. Markowitz, G., and Rosner, D. The illusion of medical certainty: Silicosis and the politics of industrial disability, 1930–1960. Milbank Quarterly 1989; 67(2, Part 1):228-253. 11. Nagi, S. Z. Some conceptual issues in disability and rehabilitation. In: M.
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The Second Fifty Years: Promoting Health and Preventing Disability B. Sussman (ed.), Sociology and Rehabilitation. Washington, D.C.: American Sociological Society, 1965. 12. Nagi, S. Z. Disability Concepts and Prevalence. Presented at the Mary Switzer Memorial Seminar, Cleveland, Ohio, 1975. 13. Nagi, S. Z. An epidemiology of disability among adults in the United States. Milbank Quarterly 1976; Fall:439-467. 14. Nagi, S. Z. Appendix A. In: Institute of Medicine, Report on a National Agenda for the Prevention of Disabilities. Washington, D.C.: National Academy Press, forthcoming. 15. National Research Council, Panel on Statistics for an Aging Population. The Aging Population in the Twenty-first Century. D. Gilford (ed.), Washington, D.C.: National Academy Press, 1988. 16. Rice, D. P., and M. P. LaPlante. Chronic illness, disability, and increasing longevity. In: S. Sullivan and M. E. Lewin (eds.). The Economics and Ethics of Long-Term Care and Disability. Lanham, Md.: University Press of America, 1988, pp. 9-55. 17. U.S. Congress, Office of Technology Assessment. Health promotion/disease prevention and nutrition in the elderly. In: Technology and Aging in America, Publ. No. OTA-BA-264. Washington, D.C., June 1985. 18. World Health Organization. International Classification of Impairments, Disabilities, and Handicaps. Geneva: World Health Organization, 1980. 19. Zola, I. K. Policies and programs concerning aging and disabilities: Towards a unifying agenda. In: S. Sullivan and M. E. Lewin (eds.), The Economics and Ethics of Long-Term Care and Disability. Lanham, Md.: University Press of America, 1988.
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