Co-morbidity analysis: a strategy for understanding mortality, disability and use of health care facilities of older people.

Older people often have several co-existing health problems. The type, number, duration and severity of these problems may have an impact on longevity and maintenance of independence. Analyses of co-morbidity can assess the additive or multiplicative effect of more than one chronic condition or impairment on the risks of mortality, loss of functioning and use of health services. Three major surveys of the elderly, initiated in the past ten years, provide data for studying the added burden of multiple morbidities. These surveys are: The National Health Interview Survey-Supplement on Aging; The National Health and Nutrition Examination Survey I-Epidemiologic Follow-up Study; and The Established Populations for Epidemiologic Studies of the Elderly. Results of analyses of co-morbidity using data from these three surveys are presented. Although each analysis used a different definitional approach to estimate the co-morbidity effect, each demonstrated an associated or increased risk on the outcome.