Exceptional longevity does not result in excessive levels of disability

Happy Elderly

A person 90 years old or between 90 and 100 years old has a high risk of losing independence, but the
prevalence of independence still declines only very modestly from age 92 to 100 years.This has the advantage of little societal care cost. So with the expansion of the life span at high age, above 90 years old, fear for high societal costs seems unfounded. The reason for this being that most disabled have a high mortality rate.

We live longer mainly due to a reduction in mortality rates among the oldest-old. There is considerable concern, that an extension of life into the highest ages in any birth cohort of elderly, now or in the future, will be accompanied by very high rates of loss of independence, with great personal and societal costs. There is a longstanding debate still going on within gerontology as to whether longer life is associated with a ‘‘compression of morbidity’’, an ‘‘expansion of morbidity’’, or a combination of both.

Recent research in Denmark seems to proof this fear unfounded. A longitudinal multi assessment survey of the entire Danish 1905 cohort from 1998 to 2005 was done. The loss of physical and cognitive independence in the age range of 92 to 100 years was assessed. They studied independence, which was defined as being able to perform basic activities of daily living without assistance from other persons and having a Mini Mental State Examination (MMSE) score of 23 or higher. Overall the 1905 cohort had only a modest decline in the proportion of independent individuals at the 4 assessments between age 92 and 100 years: 39%, 36%, 32%, and 33%, with a difference between first and last assessment of 6%.

Moreover, individuals who survive into the highest ages have a health profile that is similar in many aspects to that of individuals who are 7 or 8 years younger. This suggests that most individuals can expect to experience physical decline before they die, but the postponement of this individual decline makes it possible for us to live into the fourth age.

This result supports accumulating data that the prevalence of chronic disability is decreasing among the elderly. There is also evidence that successive cohorts are living not only longer but also better.

This is a longitudinal multi-assessment survey of the entire Danish 1905 cohort and as such a study well done providing strong evidence.

Prior Cross-sectional data indicate that dependency is considerably more prevalent in the oldest-old than in the younger elderly, but these studies are unable to disentangle age effects from cohort effects, and only a few longitudinal studies have a substantial sample size of the
oldest-old many of these studies exclude institutionalized individuals, and this exclusion severely biases
the estimation of the frequency of independence at the highest ages

K. Christensen, M. McGue, I. Petersen, B. Jeune, J. W. Vaupel (2008). Exceptional longevity does not result in excessive levels of disability Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.0804931105