Effect of reproductive history, lactation, first pregnancy age and dietary habits on bone mineral density in natural postmenopausal women.

Aim: The aim of this study was to investigate the possible risk factors related with osteoporosis in women with spontaneous menopause.

Methods: Five hundred and one postmenopausal women were divided into three groups as normal, osteopenic and osteoporotic according to their bone mineral density (BMD). By face-to-face interview, parity, age at menarche, age at menopause, duration of fertility, duration of menopause, first pregnancy age, total lactation period, exercise, smoking were assessed. Women with menopause age before 40 years, surgical menopause, who had any anti-osteoporosis treatment, hormone replacement therapy at the time of BMD measurement and corticosteroid use longer than 6 months were excluded from the study.

Results: Among 501 postmenopausal women, 107 women were classified as normal, 170 as osteopenic and 224 as osteoporotic. Among demographic features of patients, there was statistically significant difference between the groups in age, BMI and parity (p < 0.001, p < 0.0001 and p = 0.002, respectively). There were statistically significant differences between the groups in case of age at menopause, duration of fertility and duration of menopause (p = 0.013, p = 0.013 and p < 0.0001, respectively). In the multivariate logistic regression analysis, BMI over 32 and fertility duration over 33 years had a statistically significant protective effect against osteoporosis (OR 0.42, CI 95 % 0.27-0.66; OR 0.36, CI 95 % 0.24-0.56, respectively), but age was positively correlated with osteoporosis (OR 1.13, CI 95 % 1.01-1.17) CONCLUSIONS: Duration of fertility (years of menstruation) longer than 33 years and body mass index higher than 32 seem to protect against postmenopausal osteoporosis. Age is also an independent risk factor for postmenopausal osteoporosis.