Determinants of Z-Score of Bone Mineral Density among Premenopausal Saudi Females in Different Age Groups: A Cross Sectional Study

This is a comparative multicenter cross-sectional study that evaluated the potential determinants of Z-scores among premenopausal Saudi women before and after the age of peak bone density. The Study concluded that for better BMD among premenopausal women, attention should be paid to early physical activity and healthy nutrition, especially vitamin D, during the childbearing period. Objective: To explore the potential determinants of Z-scores among premenopausal Saudi females in different age groups before and after the expected age of peak bone density (PBD). Methods: This multicenter comparative cross-sectional study was conducted in Madinah and Jeddah, Saudi Arabia, between August 2021 and March 2022. We recruited 886 premenopausal females (605 (68.3%) below and 281 (31.7%) at or above the age of 30). The structured pre-coded Arabic questionnaire included sociodemographic data, a BMD questionnaire, menstrual history, an Arab Teen Lifestyle Study questionnaire, and food frequency data. Metabolic Equivalents (METs) were calculated from physical activity. Analysis of serum PTH, 25(OH) vitamin D (VD) was performed with chemiluminescent immunoassay. BMD was measured with a calcaneal qualitative ultrasound. Results: Most women had age-matched Z-scores, with very few (24 (2.7%)) being non-age-matched with no identified secondary causes. Significant Z-score determinants before PBD were BMI (OR: 0.167, p = 0.003) and total METs (OR: 0.160, p < 0.005). After the age of PBD, significant predictors were parity (OR: 0.340, p = 0.042), history of vitamin D deficiency (OR: 0.352, p = 0.048), and BMI (OR: 0.497, p = 0.019). Conclusions: Early determinants of Z-scores among premenopausal women were the nutritional status and physical activity. After the age of PBD, parity and vitamin D status offer additional determinants. For better BMD, attention should be paid to early physical activity and healthy nutrition, especially for vitamin D, with intensification of efforts during the childbearing period.