Disabling effects of chronic disease and impairment

The relationship of disability to the disease or injury identified as the major disabling condition is examined and morbidity and disability rates for selected conditions are compared and the hypothesis that ‘disability is a distinct entity with characteristic causes and with features which are not necessarily related to the etiology or pathogenesis of the coextant chronic disease’ is tested.

Abstract

SE VERA L recent studies have focused on clarifying the concepts involved in disability [l-4] and on factors affecting the assessment of disability [5]. Disease or injury are clearly necessary antecedents in the development of disability. The available evidence, however, indicates little relationship between the type of chronic condition and the extent of incapacity for expected performance [6-81. This paper examines the relationship of disability to the disease or injury identified as the major disabling condition and compares morbidity and disability rates for selected conditions. The relationship of the major disabling condition to age, sex, functional limitations and socio-economic factors is also examined. In a general sense, this analysis may be considered a test of the hypothesis that ‘disability is a distinct entity with characteristic causes and with features which are not necessarily related to the etiology or pathogenesis of the coextant chronic disease . . . [l]. Anatomic and functional abnormalities are frequently used as ‘the sole or real criterion of permanent disability . . . [9]‘. The Committee on Rating of Mental and Physical Impairment has pointed out, however, that the evaluation of disability is not a purely medical function [9]. The ability to engage in gainful activity may be affected by a variety of personal, economic and environmental attributes, in addition to the medical condition or impairment. Evaluation of impairment is ‘an appraisal of the nature and extent of the patient’s illness or injury as it affects his personal efficiency in one or more activities of daily living [9 : 13’. Impairments are often defined in terms of the precipitating chronic condition, however [IO, 113, rather than in relation to the consequential performance limitations. Hirschfeld and Behan [12] have noted that physicians are trained to focus on disease entities rather than on disability. Since mental and physical disorders vary in their severity, visibility and prognosis, the predictive value of the condition classification or diagnosis for disability evaluation is questionable. Hanman [13], for example, has observed that similar impairments do not always cause similar activity limitations nor are residual capacities the same.