Reproductive risk factors for cardiovascular disease mortality among postmenopausal women in Korea: the Kangwha Cohort Study, 1985-2005

Objective: The relationship between reproductive factors and the risk of mortality from cardiovascular disease in postmenopausal women is unclear. In this study, we aimed to investigate this relationship in Korean postmenopausal women. Methods: Subcohort analysis was carried out using the data of 3,257 postmenopausal women (age, >= 55 y at study entry) from the Kangwha Cohort Study who were followed up from 1985 until 2005. Cox proportional hazards models were used to evaluate the associations between reproductive factors and cardiovascular disease mortality. Results: The risk of cardiovascular mortality in women who were 20 to 22 years old at first childbirth was 26% lower (95% CI, 0.60-0.92) than that in women younger than 20 years at first childbirth, after adjustment for age at entry, body mass index, hypertension, drinking, smoking, education, and occupation. Early first childbirth was associated with increased cardiovascular disease mortality (P trend = 0.036). The risk of coronary heart disease mortality was 51% lower in women who were 17 to 18 years old at menarche (95% CI, 0.25-0.95) than that in women who were younger than 17 years at menarche. Conclusions: An inverse relationship between age at first childbirth and the risk of cardiovascular disease mortality exists. In addition, early menarche may be a reproductive risk factor for coronary heart disease mortality.