LAUSR

BACKGROUND Although the morbidity and mortality of cardiovascular diseases (CVD) are rising in young women, the risk factors of CVD among Korean premenopausal women have not been intensively investigated. AIM To determine how age at menarche and other female reproductive factors are associated with the risk of CVD in premenopausal women. METHODS A total of 1,088,992 premenopausal women who participated in health screening in 2009 were included. The study outcomes were myocardial infarction (MI) and ischemic stroke. Cox proportional hazards regression analysis was conducted with adjustment of traditional CVD risk factors and reproductive factors. RESULTS Mean age was 43.8 ± 5.3 years (98.9%,  < 55 years), 3.5% were current smokers, and 1.2% were heavy drinkers. During a mean follow-up of 8.3years (9,032,685.9 person-years [PY]), there were 10,876 CVD events (1.0 per 1000PY).With later menarche, the risk of CVD increased;  ≤ 12 years (adjusted hazard ratio 1.04, 95% confidence interval 0.93-1.16), 13 years (reference), 14 years (1.06, 0.98-1.14), 15 years (1.15, 1.07-1.24), 16 years (1.23, 1.14-1.34), and ≥ 17 years (1.33, 1.24-1.44). Compared with non-users, oral contraceptives (OC) users (≥ 1 year) had an increased risk of CVD (1.11, 1.01-1.22) (P for trend = 0.007). CONCLUSIONS Later menarche than the mean age at menarche (13 years old) and the use of OC (≥ 1 year) were associated with a higher risk of CVD, after adjusting for traditional cardiovascular risk factors. This study suggests that female reproductive factors could be unique risk factors for CVD in premenopausal women.