Increased risk of disease, disability, and death are well-known accompaniments of old age. While disease incidence and death are the conventional indices of a society's health status, functional disability is perhaps the most consequential index when dealing with health in old age. This chapter defines the character and magnitude of disability in old age, reviews preventive and restorative approaches to specific and general causes of disability among the elderly, and examines the role of health-care organizations in facilitating the delivery of such services.
DIMENSIONS OF THE PROBLEM
Concept and Measurement of Disability
Conceptually disability has been classified by the World Health Organization as part of a continuum of stages of disease impact that include:1
The loss or abnormality of psychological, physiological, or anatomical integrity at the level of specific organ systems.
The inability to perform an activity within the range considered normal for a human being, hence a functional limitation experienced at the level of the person as a whole.
A disadvantage resulting from an impairment or disability which if not addressed, limits an individual's ability to fulfill certain desired social roles.
Collectively this continuum has been referred to as the “disablement model.” Figure 71-l depicts the conditions, which characterize dysfunction at each of the three stages of the model, and the types of functional assessment and medical, restorative, and social intervention appropriate to maintaining and improving function and limiting disability at each stage.
The functional approach to medical care and the disablement model.
A wide variety of systems have been developed for measuring functional ability/disability.2 The best-known of these are the Activities of Daily Living (ADL) and the Instrumental Activities of Daily Living (IADL) indices. The ADL index, first introduced by Katz and colleagues, classifies limitations in six fundamental, sociobiological functions of daily living: bathing, dressing, toileting, transferring from bed or chair, continence, and feeding.3 Lawton and others broadened the scope with the IADL concept which incorporates measures of more complex adaptive or self-maintaining functions such as housekeeping, money management, and grocery shopping.4 In addition to screening and care planning for individual patients, these measurement systems have been very useful for describing the disability status of the elderly population, estimating community and institutional service needs, and evaluating outcomes of interventions designed to limit disability.
The emerging concept of “preclinical disability” focuses on identifying stages in the natural history of functional loss, which precede the onset of overt ADL or IADL dependencies. This phenomenon was originally measured in terms of adaptive modifications in the performance of common tasks such as doing housework or getting out of bed....