If the pace of increase in life expectancy in developed countries over the past two centuries continues through the 21st century, most babies born since 2000 in France, Germany, Italy, the UK, the USA, Canada, Japan, and other countries with long life expectancies will celebrate their 100th birthdays. Although trends differ between countries, populations of nearly all such countries are ageing as a result of low fertility, low immigration, and long lives. A key question is: are increases in life expectancy accompanied by a concurrent postponement of functional limitations and disability? The answer is still open, but research suggests that ageing processes are modifiable and that people are living longer without severe disability. This finding, together with technological and medical development and redistribution of work, will be important for our chances to meet the challenges of ageing populations.

Life table methods are developed for populations whose members differ in their endowment for longevity. Unlike standard methods, which ignore such heterogeneity, these methods use different calculations to construct cohort, period, and individual life tables. The results imply that standard methods overestimate current life expectancy and potential gains in life expectancy from health and safety interventions, while underestimating rates of individual aging, past progress in reducing mortality, and mortality differentials between pairs of populations. Calculations based on Swedish mortality data suggest that these errors may be important, especially in old age.

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Evolution drives, and is driven by, demography. A genotype moulds its phenotype’s age patterns of mortality and fertility in an environment; these two patterns in turn determine the genotype’s fitness in that environment. Hence, to understand the evolution of ageing, age patterns of mortality and reproduction need to be compared for species across the tree of life. However, few studies have done so and only for a limited range of taxa. Here we contrast standardized patterns over age for 11 mammals, 12 other vertebrates, 10 invertebrates, 12 vascular plants and a green alga. Although it has been predicted that evolution should inevitably lead to increasing mortality and declining fertility with age after maturity, there is great variation among these species, including increasing, constant, decreasing, humped and bowed trajectories for both long- and short-lived species. This diversity challenges theoreticians to develop broader perspectives on the evolution of ageing and empiricists to study the demography of more species.

Human senescence has been delayed by a decade. This finding, documented in 1994 and bolstered since, is a fundamental discovery about the biology of human ageing, and one with profound implications for individuals, society and the economy. Remarkably, the rate of deterioration with age seems to be constant across individuals and over time: it seems that death is being delayed because people are reaching old age in better health. Research by demographers, epidemiologists and other biomedical researchers suggests that further progress is likely to be made in advancing the frontier of survival — and healthy survival — to even greater ages.

Old-age survival has increased substantially since 1950. Death rates decelerate with age for insects, worms, and yeast, as well as humans. This evidence of extended postreproductive survival is puzzling. Three biodemographic insights--concerning the correlation of death rates across age, individual differences in survival chances, and induced alterations in age patterns of fertility and mortality--offer clues and suggest research on the failure of complicated systems, on new demographic equations for evolutionary theory, and on fertility-longevity interactions. Nongenetic changes account for increases in human life-spans to date. Explication of these causes and the genetic license for extended survival, as well as discovery of genes and other survival attributes affecting longevity, will lead to even longer lives.

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Background The oldest-old (≥80 years) are the most rapidly growing age group globally, and they are most in need of health care and assistance. The aim of this study was to explore whether increased longevity is leading to populations of healthier oldest-old (compression of disability; benefits of success), or to less healthy and disabled oldest-old (expansion of disability, costs of success). Methods Data are from Chinese Longitudinal Healthy Longevity Study (CLHLS). Three pairs of cohorts aged 80–89, 90–99 and 100–105 (in total 19,528 oldest-old participants) were examined; the two cohorts in each pair were born ten years apart, with the same age at the time of the assessment in the CLHLS 1998 and 2008 surveys. Findings Controlling for various confounding factors, compared to cohorts born 10-years earlier, death rates at oldest-old ages among later cohorts were substantially reduced annually by 0.2%–1.3%, and their disabilities of Activities of Daily Living had significantly reduced annually by 0.8%–2.6%; however, the later cohorts’ cognitive impairment rates increased annually by 0.7%–2.2% and objective physical performance capacity (stand-up from a chair, pick-up a book from floor, turning around 360°) decreased annually by 0.4%–3.8%. We also found that mortality of female oldest-old was substantially lower, but their functional capacities in ADL, cognition and physical performance were worse, compared to their male counterparts (mostly P<0.001). Interpretation These empirical findings can be explained by the theoretical framework of mixed effects of two opposing processes: advances in medications, lifestyle and socioeconomics may compress ADL disability, that is, “benefits of success”, but lifespan extension may expand disability of physical and cognitive functioning as more frail elderly survive with health problems, that is “costs of success”. Recent improvements in living standards and availability of facilities for daily living among Chinese elderly may also contribute to the contrasting trends of ADL disability and physical performance.