Differential effect of predictors of bone mineral density and hip geometry in postmenopausal women: a cross-sectional study

.Summary Osteoporosis is an important health problem in postmenopausal women. Lactation duration (LD), parity, menopause duration (MD), and body mass index (BMI) are important predictors of bone mineral density (BMD) and osteoporotic fractures in them. In addition, they have site-specific effects on BMD. Introduction Osteoporosis is especially prevalent in postmenopausal women. The aim of the study was to determine the effects of age, parity, LD, MD, and BMI on BMD at different sites and hip geometry in postmenopausal women. Materials and methods In this cross-sectional study, 87 women (45 years and above and at least 5 years postmenopausal) were enrolled. Subjects were divided into three parity groups (group 1: <= 2 children, group: 3-4 children, and group 3: >4 children) and three LD groups (group 1: <4 years, group 2: 4-8 years, and group 3: >8 years). BMD was measured at neck of femur (BMD-NF), trochanter (BMD-TR), inter-trochanter (BMD-IT), spine (BMD-LS), and forearm (BMD-FA). Hip geometry was analyzed based on dual energy X-ray absorptiometry. One way ANOVA was used for comparisons of groups, and Bonferroni correction was used as post-hoc test. p value <0.05 was considered significant. Results A significant difference in mean BMD was found between parity groups 1 and 3 at BMD-NF, BMD-TR, and BMD-LS, and between LD groups 1 and 3 at BMD-NF, BMD-TR, BMD-IT, and BMD-LS. Mean buckling ratio (BR) at IT was significantly different between parity groups 1 and 3, and LD groups 1 and 3. In multivariate regression analysis, BMI, age, and parity were significant predictors for BMD-NF; parity, BMI, and MD for BMD-TR; BMI, MD, and LD for BMD-IT; BMI and LD for BMD-LS; and age, LD, and BMI for BMD-FA. BMI and LD were significant predictors of IT-BR, while MD and BMI of narrow neck BR. Conclusion MD, LD, parity, BMI, and age are important factors influencing BMD at hip and spine in postmenopausal women, and have site-specific effects on BMD.