Association of life-course reproductive duration with mortality: a population-based twin cohort study

Background Although age at menopause has been linked to mortality, the association between the entire reproductive lifespan and mortality remains unclear. Objective This study aimed to examine to what extent life-course reproductive duration is associated with all-cause mortality and explore the role of a healthy lifestyle and familial background in such an association. Study Design A total of 11,669 women (mean age, 63.54 years) from the Swedish Twin Registry were followed for up to 19 years. Information on reproductive duration (the interval between ages at menarche and menopause) and lifestyle factors (including smoking, alcohol consumption, and physical activity; divided into unfavorable/intermediate/favorable) was collected on the basis of a structured questionnaire. Survival status was obtained from the Sweden Cause of Death Register. The data were analyzed using generalized estimating equation models, Laplace regression, and conditional logistic regression. Results In the generalized estimating equation model, compared with those with ≤34 reproductive years, the odds ratio (95% confidence interval) of all-cause mortality was 0.79 (0.68–0.90) for those with ≥40 reproductive years, which prolonged survival time by 0.84 (0.24–1.43) years. Women with ≥40 reproductive years plus a favorable lifestyle (odds ratio, 0.28; 95% confidence interval, 0.23–0.35) were at a lower risk of all-cause mortality than those with <40 reproductive years plus an unfavorable lifestyle. An additive interaction between ≥40 reproductive years and a favorable lifestyle on all-cause mortality was observed (attributable proportion, 0.584; 95% confidence interval, 0.016–1.151). The odds ratios in conditional logistic regression and generalized estimating equation models did not differ significantly (P=.67). Conclusion A longer reproductive lifespan is associated with reduced all-cause mortality and prolongs survival by 0.84 years. A favorable lifestyle may amplify the beneficial effect of longer reproductive lifespan on mortality. Familial background does not account for the observed association.