Is 70 the New 60?
The interesting data in this open access preprint paper is a concrete example of the prevailing trend in human life expectancy. A slow, steady increase in life expectancy (both at birth and remaining life expectancy at middle age) has been underway for decades, driven in part by improvements in approaches to treating age-related disease. To a first approximation, these population-wide effects on the underlying processes of aging achieved over past decades have been unintentional side-effects of progress in medical science. Deliberate targeting of the mechanisms of aging is still a comparatively new idea, and too few people are making use of approaches that may have some benefit to noticeably affect the epidemiology of the entire population.
The World Health Organization (WHO) has proposed a framework in which healthy ageing is considered not from the perspective of disease but based on an individual's ability to be and do the things they value. This ability is understood to be determined by individual-level attributes - a person's "intrinsic capacity", as well as the environments they inhabit and the interaction between the individual and these environments. Since intrinsic capacity is framed as a continuum that can be considered across the second half of life, it can potentially be used to compare incremental changes among both relatively robust and severely disabled individuals.
We have previously examined intrinsic capacity in two large longitudinal studies of the English and Chinese populations: the English Longitudinal Study on Ageing (ELSA) and the China Health and Retirement Longitudinal Study (CHARLS) Both analyses identified an intrinsic capacity construct comprising subdomains of cognitive, locomotor, sensory and psychological capacity and a further subdomain labelled vitality, which may represent underlying age-related biological changes and energy balance. The aim of this paper is to conduct a longitudinal analysis of cohort trends in intrinsic capacity in these same studies to determine whether older adults in England and China are experiencing the same, better or worse capacity than people of similar ages in the past.
Our research suggests there have been significant improvements in functioning in more recent cohorts of older people in both England and China. Within ELSA, more recent cohorts entered older ages with higher levels of intrinsic capacity, and subsequent declines were less steep than for earlier cohorts. Improvements were seen in all subdomains. The observed improvements are substantial. To avoid undue extrapolation, we limited our assessment to direct comparisons of capacity in participants of different cohorts at the same age. Currently, the overlap between adjacent cohorts in the ELSA study is 6 years, and participants of non-adjacent cohorts cannot be directly compared. However, even with these limitations, we still found that a 68-year-old ELSA participant born in 1950 had higher intrinsic capacity than a 62-year-old born just 10 years earlier.
Improvement in cognition was even more substantial. When comparing earlier cohorts, additional improvements are observed, although the gains between these cohorts are not quite as large as between the 1940 and 1950 cohorts. Thus, while our models suggest that today's 70-year-olds have the equivalent functioning to substantially younger adults in previous generations (perhaps 70 really is the new 60), our direct assessments can only confirm that 68 is the new 62.