Abstract
Evolutionary theories of senescence, such as the ‘disposable soma’ theory, propose that natural selection trades late survival for early fecundity. ‘Frailty’, a multidimensional measure of health status, may help to better define the long-term consequences of reproduction. We examined the relationship between parity and later life frailty (as measured by the Frailty Index) in a sample of 3,534 adults aged 65 years and older who participated in the English Longitudinal Study of Ageing. We found that the most parous adults were the most frail and that the parity-frailty relationship was similar for both sexes. Whilst this study provided some evidence for a ‘parity-frailty trade-off’, there was little support for our hypothesis that the physiological costs of childbearing influence later life frailty. Rather, behavioural and social factors associated with rearing many children may have contributed to the development of frailty in both sexes.
Highlights
Evolutionary theories of senescence, such as the ‘disposable soma’ theory, propose that natural selection trades late survival for early fecundity
The Frailty Index (FI) derived from the English Longitudinal Study of Ageing (ELSA) dataset had a skewed distribution with a mean score of 0.16 (standard deviation (SD) = 0.12) and a median score of 0.14 (interquartile range (IQR) = 0.08–0.24)
The proportion of participants aged 85 years and older was higher in females than males (Χ2 = 15.27, df = 4, p = 0.004) and the mean FI was higher in females than in males of the same age
Summary
Evolutionary theories of senescence, such as the ‘disposable soma’ theory, propose that natural selection trades late survival for early fecundity. The ‘disposable soma’ theory of ageing proposes that investing in reproduction, at the cost of somatic maintenance, leads to senescence[1] Evidence for this evolutionary theory was first described in studies of the fruitfly, Drosophila spp., where selecting for lifespan was associated with changes in fecundity[1]. A ‘J-shaped’ relationship between parity and mortality risk has been described by a number of studies[10,11,12] This non-linear association was found in a recent systematic review and meta-analysis, with the greatest reduction in all-cause mortality risk detected in males and females with three or four children[13]. The disposable soma theory fails to account for sex differences in longevity, whereby females consistently live longer than males[15]. Since a biological explanation for a relationship between reproduction and longevity
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