Fracture Risk and Bone Mineral Density in Metabolic Syndrome: A Meta-Analysis

Background: The risk of bone fractures in subjects with the metabolic syndrome is unknown. We did a meta-analysis to assess the association between metabolic syndrome, risk of fractures, and bone mineral density (BMD). Materials and Methods: We did searches on electronic databases (Medline, Scopus, and ISI Web of Knowledge) until December 2012 and searched reports to identify studies in humans on bone fractures and BMD at different sites. Two independent reviewers collected the relevant reports. We did random-effects meta-analyses to determine the risk of fractures and BMD values associated with metabolic syndrome. Results: A total of 17 studies, with 35 datasets, were included. In 10 articles (14 datasets) including 1350 incident and 1628 prevalent fractures, metabolic syndrome was associated with a reduced fracture risk (risk ratio = 0.85, 95% confidence interval, 0.71 - 1.00; high heterogeneity: I-2 = 55%, P = .006). Omission of 2 outlier studies resulted in a significant negative association (risk ratio = 0.85, P = .012; I-2 = 34%, P = .130). Most of the reduced fracture risk was seen in cohort studies (18% reduced risk), suggesting a direction of causality; sex, site of fracture, and definition of the syndrome did not affect the estimates. In 16 articles, including 29 341 subjects, there was no difference in spine, femoral neck, or calcaneus BMD values between subjects with or without metabolic syndrome; mean differences ranged from 0.001 to 0.012 g/cm(2) (P > .10). Conclusions: This article shows a reduced risk of bone fractures associated with metabolic syndrome, without modification of BMD. The clinical significance of these findings remains uncertain and should be addressed in future prospective studies.