Aging and the compression of disability

The age composition of the population in higher income countries has changed considerably. Signs of population aging have prompted concerns about its effects on the cost of health care systems. As people are living longer are they living healthier? On the one hand, the hypothesis of life extension, proposes that we are living longer but in poorer health. On the other hand, the optimistic hypothesis of “morbidity compression” proposes that as we live longer we spent less time in poor health.

This article evaluates these two hypothesis. The article builds on the difference between the concepts of disability and morbidity to contrast the trends in the probability and number of days in confinement to bed with the prevalence of diabetes and hypertension in Portugal over a period of almost two decades (1987-2006).

The probability of being bedridden and the average number of days confined to bed decreased significantly over time for comparable age groups (the figure above reports the evolution of the average number of days confined to bed). This reduction holds despite the evolution in the prevalence rates of the chronic diseases studied. Thus, reduced levels of disability and higher prevalence rates of chronic diseases are not mutually exclusive. It may well be the case that the reason why morbidity (prevalence) and disability are diverging is that treatments are changing and becoming more effective. To the extent it exists, compression of disability may be the result of such mechanisms.

This work therefore suggests that disability compression may be a more important aging paradigm than what the study of disease prevalence rates would indicate. Although not tackling the strict definition of morbidity compression (relative change of morbidity-free life years per increased longevity), this paper shows that similar cohorts are living better over time. In more recent cohorts, people aged 60 and over are spending considerably less time incapacitated in bed than were elderly of the same age two decades earlier - and this is happening in spite of more recent cohorts reporting higher rates of diagnosed chronic illness.

To the extent that disability and in particular severe disability are associated with high healthcare expenditures, the results of this paper imply that population aging will have a lower effect on costs than what more pessimistic approaches might predict. However, increasing rates of chronic morbidity on their own may lead to increases in healthcare expenditures. The open question is whether the changes in disability represent a reduction in morbidity severity large enough to counteract other pressures for increases in health expenditures.

Click here to go to the paper by Miguel Gouveia and Pedro Raposo.