relationship between a medical condition and the ability to work and one that is amenable to measurement via the survey process. In contrast, most contemporary theory concerning disability focuses on the complex nature of the relationship between medical conditions and disability and the importance of environmental factors, including the physical and social environments, in mediating the relationship between a medical condition and work. The first session of the workshop focused on a review of the two background papers, addressing the various conceptual frameworks, the complexity inherent in the measurement of disability, and the empirical evidence of measurement error associated with instruments that have been used to measure disability and work disability.

As discussed by Jette and Badley (see Chapter 2) both the Nagi model of disability and the model proposed in the second revision of the International Classification of Impairments, Activities, and Participation (ICIDH-2) emphasize that the accomplishment of particular social roles, such as work, involves not only the accomplishment of the particular activities related to the work task but also the ability to perform with respect to several other activity domains. For example, participation in work activities may also involve the ability to use transportation systems to get to and from work. Therefore, the inability to find accommodating transportation may result in a “work disability,” even though the individual is quite capable of performing the tasks associated with his or her occupation.

Both the Nagi and ICIDH-2 conceptual models view the disablement process as a function of the physical and social environments, accommodations and barriers within those environments, and personal attributes and resources. Work disability therefore is unlikely to be related either directly or only to a health condition or impairment. Rather, from the perspective of these conceptual models, work disability (or any other social role) is a function of the interaction of the physical and social environments, accommodations and barriers within those environments, together with the psychosocial and other attributes of the person. Therefore, the measurement of work disability should take into account personal attributes, as well as the social and physical environments in which the person operates.

The complexities of the conceptual models of disability lead to tension in the measurement of disability. The measurement of disability is further complicated by the often ambiguous and varying uses of the terms used in conceptual models and measurement instruments both within and outside the field. In addition, in light of the passage of the American with Disabilities Act, the language is evolving. These factors suggest the use of a survey instrument in which multiple questions concerning disability are asked to set the context for the measurement process, clarify terminology, and tap the multiple domains of interest. This conflicts with the desire of the Social Security Administration, as well as numerous other federal agencies, to identify a short battery of questionnaire items that can



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