Health expectancies: an overview and critical appraisal

Introduction In the last two decades, there has been a considerable international effort to develop summary measures of population health that integrate both mortality and non-fatal health outcomes, and international policy interest in such indicators is increasing. As a result, two major classes of summary measures have been developed: health expectancies, such as disability-free life expectancy; and health gaps, such as disability-adjusted life year (DALY). This chapter describes the concept of health expectancy, a taxonomy of the types of health expectancy and an overview of methods of calculation. Health expectancy is a generic term for all population indicators that estimate the average time (in years) that a person could expect to live in various states of health. Health expectancies may relate to defined states of health (breaking up the continuum of health into dichotomous or poly-chotomous states), or to equivalent years of good health (using health state valuations to calculate health-adjusted life expectancies, or disability-adjusted life expectancies). The best known example of a dichotomous health expectancy is the disability-free life expectancy at birth. This measure estimates the average expected years of life " free of disability " for a newborn in a population, if current disability and mortality conditions continue to apply. The best known example of a health-adjusted life expectancy is healthy life expectancy (HALE) calculated for 191 countries by the World Health Organization for 1999 (WHO 2000) and 2000 (WHO 2001a). This measure estimates the average equivalent " healthy " expected years of life for a newborn in a population, if current disability and mortality conditions continue to apply. This chapter also examines issues in the conceptualization, measurement and valuation of health status that must be addressed before using health expectancies as summary measures of population health. Some major methodological and empirical issues are identified that must be con-178 Summary Measures of Population Health sidered before developing a standard approach to estimating health ex-pectancies for populations. Finally, the chapter includes a critical comparison of health expectancy indicators against the desirable criteria for summary measures of population health proposed by Murray et al. (2000) and proposes a health expectancy indicator that meets all these criteria.