Summary measures of population health: addressing the first goal of healthy people 2010, improving health expectancy.

This report is one of several Healthy People Statistical Notes that evaluate methodological issues pertaining to summary measures - statistics that combine mortality and morbidity data to represent overall population health in a single number. This report evaluates the consequences of changes in the components of health expectancy measures (i.e., mortality or morbidity) on the overall measure. Any activity limitation is used as a morbidity measure. Simulations are used to evaluate the impacts of reducing 1995 age-specific mortality or activity limitation rates by 5, 10, 25, and 50 percent at all ages. Then it is limited to ages under 25 years, 25 -64 years, and over 64 years. The impact of completely eliminating mortality or activity limitation for the younger age groups is also examined. In general, reducing morbidity rates results in greater changes than the same percent reduction in death rates. The same proportional reduction in age-specific rates for either mortality or morbidity has a greater impact if it occurs at older ages. Reducing mortality results in a greater change in life expectancy than in health expectancy and a decline in the proportion of life lived in healthy states. Reducing morbidity increases both health expectancy and the proportion of life lived in healthy states. Simultaneous reductions in mortality and morbidity have additive effects on health expectancy.