Identification of the risk factors for osteoporosis among postmenopausal women

Objectives The aim of this study was to determine the effect of different durations of menopause at the time of bone mineral density (BMD) measurement and of different age at menopause intervals on the prevalence of osteopenia and osteoporosis among untreated postmenopausal women. We also assessed related factors leading to low BMD. Methods A total of 2769 postmenopausal women who had not taken any anti-osteoporosis treatment and/or hormone replacement therapy were divided into three groups according to duration of menopause at the time of BMD measurement. The women were also evaluated in four different age groups according to their age at menopause onset. Multinomial logistic regression analysis was used to determine related factors leading to low BMD. Investigated parameters include demographic characteristics, plasma glucose, lipids, and lipoproteins. Results According to World Health Organization (WHO) criteria, among 2769 patients, 449 (16.2%) were identified as having osteoporosis, 1085 (39.2%) as having osteopenia, and 1235 (44.6%) as having normal BMD. Osteoporosis was determined in 10.6% and 16.2% of women with menopause duration of 0–3 years and 4–7 years, respectively, whereas this rate was 31.9% in women with menopause duration of over 7 years (p = 0.001). The percentages for osteopenia remained constant among the three different menopause durations (0–3 years: 37.2%, 4-7 years: 42.1%, and >7 years: 40.9%). Thirty percent of women with age at onset of <40 years were osteoporotic. However, the percentages of women with osteoporosis among the other age groups were similar (40–46 years: 18.3%, 47–52 years: 14.1%, and >52 years: 15.4%). The percentages for osteopenia remained relatively constant among the four age groups (36.7, 40, 39.1 and 39%). According to the multinomial logistic regression analysis, duration of menopause at the time of BMD test and parity were positively correlated with both osteoporosis and osteopenia, while glucose level was negatively correlated with both osteoporosis and osteopenia. Age at menopause was negatively correlated only for osteoporosis. Low-density lipoprotein cholesterol (LDL-c) level may be accepted as a clinically significant factor for osteopenia (OR: 1.01; CI95%: 1.00–1.02). No differences were determined in the prevalence of osteopenia and osteoporosis in women with menopause duration of >7 years when evaluated according to the four menopause age groups as described before (p = 0.74). Contribution to the regression model was 0.8% by age at menopause, 5.6% by menopause duration at time of BMD measurement, 5.8% by both factors. Conclusion According to our results, osteoporosis is related more to the duration of menopause at the time of BMD measurement rather than the age at menopause among untreated postmenopausal women. High parity was determined as another risk factor for low BMD.