ChiCTR-TRC-09000376 (http://apps.who.int/trialsearch/).

PURPOSE The aim of this study was to evaluate the serum levels of retinoic acid (RA), an active form of vitamin A, in postmenopausal women with hip fractures from Zhengzhou, China. METHODS This was a case‐control study from the Affiliated Hospital of Zhengzhou University. Serum samples were drawn from 375 postmenopausal women who were diagnosed as having hip fracture and 750 matched controls without fracture. Serum RA levels were evaluated as both a continuous variable and a categorical variable in quintiles. RESULTS The results showed that the serum levels of RA were significantly (P = .039) higher in patients with hip fracture compared with controls. In univariate and multivariate logistic regression analysis, for each 1 ng/mL increase of serum level of RA, the unadjusted and adjusted risk of hip fracture would be increased by 5% (odds ratio [OR] = 1.05; 95% confidence interval [CI] = 1.00‐1.10; P = .035) and 2% (OR = 1.02; 95% CI = 0.95‐1.11; P = .096), respectively. In multivariate models comparing the fifth with the third quintiles of RA, the RA was associated with hip fracture, and adjusted risk of hip fracture would be increased by 52% (OR = 1.52; 95% CI = 1.13‐1.42; P = .011). CONCLUSIONS The results of our study suggest that subclinical higher levels of RA may increase the risk of hip fracture in postmenopausal women, particularly among the top quintile of serum RA. J Am Geriatr Soc 67:336–341, 2019.