Current measures to monitor population health include indicators of (i) average length-of-life (life expectancy, LE), (ii) average length-of-life spent in good health (healthy life expectancy, HLE) and (iii) variability in length-of-life (lifespan inequality, LI). While HLE indicators crucially distinguish between ‘quantity’ and ‘quality’ of years of life, they are population-level averages, so they do not capture the ‘equality’ dimension of health. Alternatively, LI indicators measure individual-level variability in ages at death, but they fail to distinguish between the years spent in good health and the years spent in less-than-good health – even if the normative desirability of the latter is unclear. Thus, we lack population health indicators that simultaneously capture the ‘quality’ and ‘equality’ dimensions of health. To fill this empirical gap, Iñaki Permanyer, Jeroen Spijker and Amand Blanes (Centre d’Estudis Demogràfics,) introduce the concept of ‘healthy lifespan inequality’ (HLI), which is designed to investigate the extent to which healthy lifespans are (un)equally distributed across population members.
There are several reasons why HLI can be considered a fundamental quantity in health research that should be reported alongside other well-known mortality and morbidity summary indicators like LE, HLE and LI. First, population health means more than simply averting death. Societies are concerned not only about average levels of disease and/or disability but also about the patterns in which the latter are distributed. Second, the new HLI indicators measure variability in the timing of disease, disability or physical limitation (i.e., morbidity) onset, and thus it aims at capturing a fundamental aspect of population health that has been largely overlooked in the literature.
Applying the new indicator across education groups in contemporary Spain, two important findings arise. First, the authors observe that HLI tends to decrease with increasing educational attainment, both for women and men. Thus, low-educated individuals tend to not only die earlier and spend a shorter portion of their lives in good health than their highly educated counterparts, but they also face greater variation in the eventual time of death and in the age at which they cease enjoying good health. These multiple burdens of inequality should be taken into consideration when evaluating the performance of public health systems and in the elaboration of realistic working-life extension plans and the design of equitable pension reforms.
Second, results indicate that the variability in the ages at which physical daily activity limitations start (HLI) is substantially larger than the variability in the ages at which individuals die (LI). Therefore, the new indicator not only uncover new layers of health inequality that are not traceable with currently existing approaches, but it also hints at the fact that morbidity-related inequalities might be more prominent than mortality-related ones. Future research should extend such analyses to other countries and explore how the new indicators can contribute towards a general theory on population ageing.