James W. Vaupel

Ageing populations: the challenges ahead

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.

The impact of heterogeneity in individual frailty on the dynamics of mortality

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.

The heritability of human longevity: A population-based study of 2872 Danish twin pairs born 1870–1900

The aim of this study was to explore, in a large and non-censored twin cohort, the nature (i.e., additive versus non-additive) and magnitude (i.e., heritability) of genetic influences on inter-individual differences in human longevity. The sample comprised all identified and traced non-emigrant like-sex twin pairs born in Denmark during the period 1870–1900 with a zygosity diagnosis and both members of the pairs surviving the age of 15 years. A total of 2872 pairs were included. Age at death was obtained from the Danish Central Person Register, the Danish Cause-of-Death Register and various other registers. The sample was almost non-censored on the date of the last follow-up (May 1, 1994), all but 0.6% had died, leaving a total of 2872 pairs for analysis. Proportions of variance attributable to genetic and environmental factors were assessed from variance-covariance matrices using the structural equation model approach. The most parsimonious explanation of the data was provided by a model that included genetic dominance (non-additive genetic effects caused by interaction within gene loci) and non-shared environmental factors (environmental factors that are individual-specific and not shared in a family). The heritability of longevity was estimated to be 0.26 for males and 0.23 for females. The small sex-difference was caused by a greater impact of non-shared environmental factors in the females. Heritability was found to be constant over the three 10-year birth cohorts included. Thus, longevity seems to be only moderately heritable. The nature of genetic influences on longevity is probably non-additive and environmental influences non-shared. There is no evidence for an impact of shared (family) environment.

Biodemography of human ageing

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.

The quest for genetic determinants of human longevity: challenges and insights

Twin studies show that genetic differences account for about a quarter of the variance in adult human lifespan. Common polymorphisms that have a modest effect on lifespan have been identified in one gene, APOE, providing hope that other genetic determinants can be uncovered. However, although variants with substantial beneficial effects have been proposed to exist and several candidates have been put forward, their effects have yet to be confirmed. Human studies of longevity face numerous theoretical and logistical challenges, as the determinants of lifespan are extraordinarily complex. However, large-scale linkage studies of long-lived families, longitudinal candidate-gene association studies and the development of analytical methods provide the potential for future progress.

Lifespan depends on month of birth

Month of birth influences adult life expectancy at ages 50+. Why? In two countries of the Northern Hemisphere–Austria and Denmark–people born in autumn (October–December) live longer than those born in spring (April–June). Data for Australia show that, in the Southern Hemisphere, the pattern is shifted by half a year. The lifespan pattern of British immigrants to Australia is similar to that of Austrians and Danes and significantly different from that of Australians. These findings are based on population data with more than a million observations and little or no selectivity. The differences in lifespan are independent of the seasonal distribution of deaths and the social differences in the seasonal distribution of births. In the Northern Hemisphere, the excess mortality in the first year of life of infants born in spring does not support the explanation of selective infant survival. Instead, remaining life expectancy at age 50 appears to depend on factors that arise in utero or early in infancy and that increase susceptibility to diseases later in life. This result is consistent with the finding that, at the turn of the last century, infants born in autumn had higher birth weights than those born in other seasons. Furthermore, differences in adult lifespan by month of birth decrease over time and are significantly smaller in more recent cohorts, which benefited from substantial improvements in maternal and infant health.

Diversity of ageing across the tree of life

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.

Reductions in mortality at advanced ages: several decades of evidence from 27 countries.

It is widely assumed that mortality at advanced ages is attributable to old age per se and that death rates at advanced ages cannot be substantially reduced. Using a larger body of data than previously available the authors find that developed countries have made progress in reducing death rates even at the highest ages. Furthermore the pace of this progress has accelerated over the course of the twentieth century. In most developed countries outside Eastern Europe average death rates at ages 80-99 have declined at a rate of 1 to 2 percent per year for females and 0.5 to 1.5 percent per year for males since the 1960s. For an aggregate of nine countries with reliable data through 1991 the annual average rate of improvement between 1982-86 and 1987-91 was 1.7 percent for male octogenarians and 2.5 percent for female octogenarians. (SUMMARY IN FRE AND SPA) (EXCERPT)

Mortality among twins after age 6: fetal origins hypothesis versus twin method.

Abstract Objective: To test the validity of the fetal origins hypothesis and the classic twin method. Design: Follow up study of pairs of same sex twins in which both twins survived to age 6. Setting: Denmark. Subjects: 8495 twin individuals born 1870-1900, followed through to 31 December 1991. Main outcome measures: Mortality calculated on a cohort basis. Results: Mortality among twins and the general population was not significantly different except among females aged 60-89, in whom mortality among twins was 1.14 times (SE 0.03) higher than in the general population. Mortality among female dizygotic twins was 1.77 times (0.18) higher than among monozygotic twins at age 30.59. Otherwise, mortality for monozygotic and dizygotic twins did not consistently differ after age 6. Conclusion: According to the fetal origins hypothesis the risk of adult morbidity and mortality is heightened by retardation in intrauterine growth. Twins, and in particular monozygotic twins, experience growth retardation in utero. The findings in the present study suggest that the fetal origins hypothesis is not true for the retardation in intrauterine growth experienced by twins. Furthermore, the data are inconsistent with the underlying assumption of a recent claim that the classic twin method is invalid for studies of adult diseases. The present study is, however, based on the one third of all pairs of twins in which both twins survived to age 6. The possible impact of this selection can be evaluated in future studies of cohorts of younger twins with lower perinatal and infant mortality. Key messages Key messages It has been claimed that twin studies of adult diseases are invalid owing to the link between intrauterine development and adult diseases Contrary to the prediction from the fetal origins hypothesis this study found that mortality among twins and in the general population was similar after age 6 Contrary to the underlying assumption of the claim that the twin method is invalid, this study found that mortality in monozygotic and dizygotic twins was similar after age 6 This study suggests that the fetal origins hypothesis is not true for the retardation in intrauterine growth in these twin cohorts and that the hypothesis is no threat to the validity of the twin method

Survival after the Age of 80 in the United States, Sweden, France, England, and Japan

BACKGROUND In many developed countries, life expectancy at birth is higher than in the United States. Newly available data permit, for the first time, reliable cross-national comparisons of mortality among persons 80 years of age or older. Such comparisons are important, because in many developed countries more than half of women and a third of men now die after the age of 80. METHODS We used extinct-cohort methods to assess mortality in Japan, Sweden, France, and England (including Wales) and among U.S. whites for cohorts born from 1880 to 1894, and used cross-sectional data for the year 1987. Extinct-cohort methods rely on continuously collected data from death certificates and do not use the less reliable data from censuses. RESULTS In the United States, life expectancy at the age of 80 and survival from the ages of 80 to 100 significantly exceeded life expectancy in Sweden, France, England, and Japan (P < 0.01). This finding was confirmed with accurate cross-sectional data for 1987. The average life expectancy in the United States is 9.1 years for 80-year-old white women and 7.0 years for 80-year-old white men. CONCLUSIONS For people 80 years old or older, life expectancy is greater in the United States than it is in Sweden, France, England, and Japan. This finding suggests that elderly Americans are receiving better health care than the elderly citizens of other developed countries.