B Vitamins and Hip Fracture: Secondary Analyses and Extended Follow-Up of Two Large Randomized Controlled Trials

Elevated plasma homocysteine levels are associated with increased risk of fractures in observational studies. However, it is unsettled whether homocysteine-lowering treatment affects fracture risk. The aim of this study was to investigate the effect of an intervention with B vitamins on the risk of hip fracture in a secondary analysis of combined data from two large randomized controlled trials originally designed to study cardiovascular diseases. Both trials had identical design, intervention, and primary objective. Based on a two-by-two factorial design, the intervention consisted of a daily capsule with either (1) folic acid (0.8mg) plus vitamin B-12 (0.4mg) and vitamin B-6 (40mg); (2) folic acid (0.8mg) plus vitamin B-12 (0.4mg); (3) vitamin B-6 alone (40mg); or (4) placebo. The participants were followed with respect to hip fracture during the trial or during an extended follow-up (from the trial start for each patient until the end of 2012). No statistically significant association was found between folic acid plus vitamin B-12 treatment and the risk of hip fracture, neither during the trial (median 3.3 years; hazard ratio [HR] 0.87; 95% confidence interval [CI], 0.48 to 1.59) nor during the extended follow-up (median 11.1 years; HR 1.08; 95% CI, 0.84 to 1.40). Nor were there significant differences in the risk of hip fracture between groups receiving versus not receiving vitamin B-6 during the trial (HR 1.42; 95% CI, 0.78 to 2.61). However, during the extended follow-up, those receiving vitamin B-6 showed a significant 42% higher risk of hip fracture (HR 1.42; 95% CI, 1.09 to 1.83) compared to those not receiving vitamin B-6. In conclusion, treatment with folic acid plus vitamin B-12 was not associated with the risk of hip fracture. Treatment with a high dose of vitamin B-6 was associated with a slightly increased risk of hip fracture during the extended follow-up (in-trial plus post-trial follow-up). (C) 2017 American Society for Bone and Mineral Research.