Understanding the Cross-Sectional Association Between Life Expectancy and Healthy Life Years: The CroHaM Hypothesis

A central question of interdisciplinary health research is whether the life years gained through increasing life expectancy are primarily spent in good or poor health. Two opposing models have been proposed: "expansion of morbidity" and "compression of morbidity". Existing research based on longitudinal data and time series has supported both approaches, depending on the particular dimension of health under consideration. In this paper we hypothesize that the longitudinal health dimension-specific expansion and compression effects exist equivalently in the cross-sectional association between health and mortality (CroHaM), affecting differences in the number of healthy life years between populations and subpopulations with different levels of life expectancy. The CroHaM hypothesis roots in the observation that most health differentials within and between populations are caused primarily by social factors and it builds on Link and Phelan's "theory of fundamental social causes" (1995). We present empirical support for the hypothesis by analyzing the relationship between life expectancy and healthy life years on the basis of different health dimensions for a sample of female and male Catholic order members and their counterparts in the general populations of Germany and Austria. Finally, we outline that the CroHaM hypothesis may also contribute to a better understanding of differences in life years spent in good or poor health and make suggestions for further testing of the CroHaM hypothesis.