Epidemiological approaches to disability in the elderly: from measurement to the projection of need.

Measures of disability, in the elderly as a proxy for autonomy, are essential for assessment of physical and mental wellbeing, estimates of needs for care of individuals and communities and for the planning of services. Such measures need to be combined with clinical information to complete the diagnosis for the individual. For groups, assessments are subject to the interactions of reported disability with age, social class and culture, even when using standardized questionnaires. These intervening variables, as well as the representatives of the groups sampled, must be considered when extrapolating the findings to the whole population and, particularly, in the forecasting of future disability patterns. Translation of disability measurements into needs for service, now and in the future, is a complex procedure further confounded by social expectations and professional judgement.