Health, functioning, and disability in older adults--present status and future implications.

Ageing is a dynamic process, and trends in the health status of older adults aged at least 60 years vary over time because of several factors. We examined reported trends in morbidity and mortality in older adults during the past two decades to identify patterns of ageing across the world. We showed some evidence for compression of morbidity (ie, a reduced amount of time spent in worse health), in four types of studies: 1) of good quality based on assessment criteria scores; 2) those in which a disability-related or impairment-related measure of morbidity was used; 3) longitudinal studies; or 4) studies undertaken in the USA and other high-income countries. Many studies, however, reported contrasting evidence (ie, for an expansion of morbidity), but with different methods, these measures are not directly comparable. Expansion of morbidity was more common when trends in chronic disease prevalence were studied. Our secondary analysis of data from longitudinal ageing surveys presents similar results. However, patterns of limitations in functioning vary substantially between countries and within countries over time, with no discernible explanation. Data from low-income countries are very sparse, and efforts to obtain information about the health of older adults in less-developed regions of the world are urgently needed. We especially need studies that focus on refining measurements of health, functioning, and disability in older people, with a core set of domains of functioning, that investigate the effects of these evolving patterns on the health-care system and their economic implications.