Association between serum zinc concentration and fracture risk in postmenopausal women: a 9-year cohort study

The association between serum zinc (SZn) concentration and fracture risk in postmenopausal women was investigated.

Women (n = 851) with a history of natural, premature, or surgical menopause who had completed data, including SZn concentrations at baseline (2009-2011), were included and followed through March 2018 for the incidence of any fracture requiring inpatient care. Potential non-linear and dose-response associations between SZn and fracture risk were assessed using a restricted cubic spline model (RCS) in Cox regression with the likelihood ratio test (LRT). Multivariable Cox proportional hazard models were used to estimate adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) of fractures across the categories of SZn [< 86, 86-135 (as reference), and ≥ 135 μg/dL].

During a median follow-up period of 8.8 years (interquartile range: 8.1-9.2 years), 4.3% of postmenopausal women (with a mean age of 61.4 ± 8.6 years) experienced a new incident fracture. The mean of baseline SZn concentration was 113 ± 39.3 μg/dL. The LRT indicated no significant non-linear association (P = 0.176) and no evidence of a dose-response relationship (P = 0.448) between SZn and fracture risk. Using the categorical approach, the multivariable-adjusted Cox model showed that postmenopausal women with SZn concentrations below 86 μg/dL had a significantly increased risk of fracture compared to those within the reference range (86-135 μg/dL), with an HR of 2.29 (95% CI = 1.02-5.16, P = 0.044). SZn concentrations exceeding the reference range (≥ 135 μg/dL) were not associated with risk of fractures (HR = 1.47, 95% CI = 0.61-3.58).

Suboptimal SZn levels, indicative of inadequate zinc status, may contribute to an increased risk of bone fractures in postmenopausal women.