Reproductive Lifespan and Chronic Disease Risk in Aging Women: A Scoping Review of Longitudinal Evidence

Reproductive lifespan, defined as the total interval in years from onset of menarche to age at natural menopause, represents the most integrated available proxy for cumulative endogenous estrogen exposure across a woman's life course. Despite substantial published evidence linking individual reproductive markers such as age at natural menopause and age at menarche to specific chronic disease outcomes, no scoping review has comprehensively mapped longitudinal evidence treating reproductive lifespan as a primary integrated exposure variable across multiple aging outcome domains. This scoping review follows the JBI methodological framework for scoping reviews (Peters et al., 2020) and will be reported according to the PRISMA Extension for Scoping Reviews (PRISMA-ScR; Tricco et al., 2018). Six electronic databases will be searched: MEDLINE via PubMed, EMBASE via Ovid, CINAHL Plus, PsycINFO, Web of Science Core Collection, and Scopus. Eligible studies are longitudinal observational designs (prospective cohort, retrospective cohort, or nested case-control) examining the association between reproductive lifespan and any chronic disease outcome in postmenopausal women aged 40 years or older, with a minimum sample size of 500 participants. Outcomes of interest span five domains: cardiometabolic disease, cognitive and neurological outcomes, functional and musculoskeletal outcomes, oncological outcomes, and mortality. Records will be de-duplicated and independently screened by two reviewers at title-abstract and full-text stages using Rayyan. Data will be charted using a standardized extraction form covering study design, exposure operationalization, outcome definition, analytic approach, covariate adjustment, and key findings. Synthesis will be entirely narrative; no meta-analytic pooling will be performed. The review will produce an evidence gap map identifying which combinations of reproductive lifespan exposure definition and chronic disease outcome domain remain unaddressed in longitudinal literature, providing the empirical foundation for subsequent primary research using the Canadian Longitudinal Study on Aging.