The association between common vitamin D receptor gene variations and osteoporosis: A participant-level meta-analysis

Background: Polymorphisms of the vitamin D receptor (VDR) gene have been implicated in the genetic regulation of bone mineral density (BMD). However, the clinical impact of these variants remains unclear. Objective: To evaluate the relation between VDR polymorphisms, BMD, and fractures. Design: Prospective multicenter large-scale association study. Setting: The Genetic Markers for Osteoporosis consortium, involving 9 European research teams. Participants: 26242 participants (18405 women). Measurements: Cdx2 promoter, FokI, BsmI, ApaI, and TaqI polymorphisms; BMD at the femoral neck and the lumbar spine by dual x-ray absorptiometry; and fractures. Results: Comparisons of BMD at the lumbar spine and femoral neck showed nonsignificant differences less than 0.011 g/cm(2) for any genotype with or without adjustments. A total of 6067 participants reported a history of fracture, and 2088 had vertebral fractures. For all VDR alleles, odds ratios for fractures were very close to 1.00 (range, 0.98 to 1.02) and collectively the 95% CIs ranged from 0.94 (lowest) to 1.07 (highest). For vertebral fractures, we observed a 9% (95% CI, 0% to 18%; P = 0.039) risk reduction for the Cdx2 A-allele (13% risk reduction in a dominant model). Limitations: The authors analyzed only selected VDR polymorphisms. Heterogeneity was detected in some analyses and may reflect some differences in collection of fracture data across cohorts. Not all fractures were related to osteoporosis. Conclusions: The FokI, BsmI, ApaI, and TaqI VDR polymorphisms are not associated with BMD or with fractures, but the Cdx2 polymorphism may be associated with risk for vertebral fractures.