Pregnancy history is associated with lower odds of osteoporosis among Taiwanese women

BACKGROUND: Osteoporosis is a major public health concern worldwide. Although female reproductive factors have been suggested to influence bone health, their associations with osteoporosis remain inconclusive. OBJECTIVE: This study aimed to investigate the associations between reproductive characteristics and the odds of osteoporosis in Taiwanese women. METHODS: We conducted a cross-sectional analysis using data from women randomly selected from the Taiwan Biobank. Bone mineral density (BMD) status was classified into three categories according to the World Health Organization (WHO) criteria: normal BMD (T-score > - 1.0), osteopenia (- 2.5 < T-score ≤ - 1.0), and osteoporosis (T-score ≤ - 2.5). Univariable and multivariable logistic regression analyses were performed to assess the association between reproductive factors and the odds of BMD status. RESULTS: Among the 4,854 participants, 3,107 (64.0%) were classified as having normal BMD, 1,374 (28.3%) as having osteopenia, and 373 (7.7%) as having osteoporosis. Univariate analysis showed that a history of pregnancy was associated with a higher odd of osteopenia (odds ratio [OR] = 1.946, 95% CI: 1.589-2.382, p < 0.001), osteoporosis (OR = 1.825, 95% CI: 1.288-2.586, p = 0.001), and low BMD level (T-score < -0.1) (OR = 1.919, 95% CI: 1.597-2.306, p < 0.001). After adjusting for known confounders, pregnancy history was associated with a lower odd of osteoporosis (adjusted OR = 0.644, 95% CI: 0.422-0.981, p = 0.041), but not significantly associated with the odds of osteopenia or low BMD level. CONCLUSIONS: Pregnancy history was independently associated with lower odds of osteoporosis among Taiwanese women after adjustment for known confounding factors. However, given the cross-sectional nature of this study, causal relationships cannot be established. Future longitudinal studies are warranted to validate this finding.