The present study analyzes data from individual twins to examine phenotypic associations between reproductive timing and AD, and in subsidiary analyses, pair-level data to examine heritable sources of covariation. Because not all respondents, particularly those in the young cohort, had aged through periods of highest likelihood of childbearing, time-to-event data were analyzed using survival analysis. Associations between AD and reproductive onset were examined separately for women and men within cohort given i) both cohort and sex differences in the prevalence of AD, and ii) cohort differences in the assessment of AD, including availability of age of onset measures.
