in which the impact of health conditions can been conceptualized as having 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, attitudes of employers or coworkers, and other restrictions) that might prevent 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 endpoint, 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 measurement 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



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