14 August 2017:
In this ageing world, the field of the 'epidemiology of longevity' has been expanding rapidly in recent years. With a dramatic increase in survival rate to advanced old age over the past century, longevity can be described as an epidemic. Many studies have evaluated the impact of factors such as low socioeconomics in childhood, genetics, environmental, dietary and lifestyle (smoking and alcohol use), which negatively affect longevity. Although mortality rates for females are lower at each age than those of men, a close association between reproductive characteristics and longevity was recently documented.
Several reproductive factors, such as the age at first birth, parity and age of menopause, have been found to be associated with women's longevity. The recent prospective (WHI) study, in a large multi-ethnic cohort of postmenopausal women, examined 20,248 women from 40 clinical centers (aged 50–79 years, mean age at baseline 74.6 years); 10,909 (54%) of these women survived to age 90 years . The odds of longevity were significantly higher in women with later age at first childbirth (adjusted odds ratio 1.11; 95% confidence interval 1.02–1.21 for age 25 years or older vs. younger than 25 years; p for trend = 0.04). Among parous women, the relationship between parity and longevity was significant among White but not Black women, while women with two to four term pregnancies compared with one term pregnancy had higher odds of longevity. This long-term, follow-up study reported that a rising number of pregnancies were associated with higher likelihood of longevity in the participants who survived to the age of 90 years. It was pointed that this was independent of demographic characteristics, socioeconomic position, lifestyle behaviors, reproductive factors and health-related factors. Despite these strengths, the authors pointed at a limitation of the study: women included in this study were on average aged 75 years at enrolment and may have had a higher likelihood of achieving longevity as they had already survived to their seventies. Also, with respect to historical events, participants may have had different experiences that may have influenced their life expectancy. So, because of potential selection bias, this cannot be applicable to the general population of childbearing women.