Menstrual and reproductive factors and fracture risk: The Leisure World Cohort study

Background: Because menopausal estrogen is related to the development of osteoporosis, we investigated the potential associations of the estrogen-related events of menarche, pregnancy, and menopause with fracture risk in a population-based, prospective study of older women. Methods: The Leisure World Cohort was established in the early 1980s when residents of a California retirement community, including 8877 women, completed a health survey. Incident fractures of the hip (n = 1220), wrist (n = 463), and spine (n = 613) incurred over two decades were identified from four follow-up questionnaires, hospital discharge records, and ( for hip fracture) death certificates. Hazard ratios (HR) adjusted for age and other potential confounders were calculated using proportional hazards regression. Results: Late age at menarche was associated with decreased hip fracture risk (HR = 0.84, 95% CI 0.72-0.98, for age >= 14 vs. <= 12 years) but was unrelated to fractures at other sites. Hip fracture risk was also reduced in women who had been pregnant (HR = 0.83, 95% CI 0.72-0.95). Women who reported menopause at age 45+ had a lower risk of wrist fracture compared with those with menopause at age <= 44 (HR = 0.74, 95% CI 0.58-0.95 for ages 45-54; HR = 0.71, 95% CI 0.49-1.04 for ages 55+). Although fracture risks did not differ between ever and never users of menopausal estrogen, recency since last use was related to wrist fractures (HR = 1.09, 95% CI 1.03-1.16 for each 5 years since last years). Conclusions: The estrogen-related events of menarche, pregnancy, and menopause were not associated with osteoporotic fracture risk in a consistent manner. Other factors related to these events may be influencing development of osteoporosis and the likelihood of sustaining a fracture in older women.