CONTEXT: Menstrual cycle characteristics may be associated with cardiovascular disease (CVD) risk.

OBJECTIVE: The objective of this study was to describe the relationships between menstrual cycle characteristics and daily reproductive hormone measures with CVD risk factors in middle-aged women.

DESIGN AND SETTING: Cross-sectional associations were examined between CVD risk factors and urinary LH, FSH, estrone conjugates, and pregnanediol glucuronide (Pdg) measured across one menstrual cycle or 50 d.

PARTICIPANTS: Menstruating women (n = 500) who were free from diabetes or past stroke or heart attack enrolled in the Daily Hormone Study-Study of Women's Health across the Nation were studied.

MAIN OUTCOME MEASURES: Body mass index (BMI), blood pressure, hemostatic, and metabolic factors were measured. RESULTS: Few differences existed in risk factors between women with evidence of luteal activity and those with no evidence of luteal activity. Associations between elevated CVD risk factors and long cycle length were reduced substantially by age and BMI adjustments. Those with lower estrone conjugate and PdG averaged across the follicular phase had higher waist circumference, triglycerides, insulin, plasminogen activator inhibitor type-1, tissue type plasminogen activator-antigen, and factor VIIc levels in age- and BMI-adjusted analyses (P < 0.05).

CONCLUSIONS: In midlife menstruating women, a longer cycle length was related to CVD risk factors, in large part through their common association with BMI. More favorable levels of metabolic and hemostatic factors were associated with higher levels of follicular-phase estrogen, a pattern consistent with a more competent ovary, and higher levels of follicular-phase PdG, perhaps of adrenal origin. Metabolic and hemostatic factors may be sensitive to hormonal variation during the early perimenopausal transition.