Life expectancy free of disability: a composite measure of population health status.

Access to disability data from a nationwide survey of New Zealanders provides the opportunity to estimate Life Expectancy Free of Disability (LEFD) for the non-institutional adult population. This measure of population health status combines mortality and morbidity data into a single index. The analysis is restricted to the 15-64 age range and results on partial life expectancy free of disability are presented for the key sociodemographic groups. The results conform to the international evidence and highlight the potential impact of disability as a component in a composite measure of population health status: although women live longer than men, almost all this apparent advantage in longevity is spent in some state of disablement; Maori are disadvantaged in comparison with non-Maori both in terms of longevity and in the proportion of the life span spent disability-free; and, social class comparisons show a decline in LEFD with declining social class that is steeper than the corresponding mortality gradient. Despite some technical difficulties and the strong requirements of the data, the LEFD measure has many potential applications in public health research and planning. In particular, it has the potential to direct research and policy towards the enhancement of the active years of life rather than just the postponement of mortality.