Summary
Evidence from one meta-analysis (12 studies) and five population-based cohort studies,
totaling more than 150,000 subjects, suggests that BMI is a significant prognostic
factor for hip fracture. Low BMI or body size was associated with increased hip fracture
risk, while high BMI was found to be protective for fracture. However, after adjustment
for bone mineral density (BMD), low BMI remained a factor for increase risk based
on the metaanalysis while higher BMI was no longer a protective factor. There was
conflicting evidence for the effect of sex-specific BMI on risk. Two studies, including
the meta-analysis, found no difference in risk estimates by sex, suggesting that the
effect of BMI on hip fracture is not different by sex. However, one study reported
that higher BMI was protective for risk of fracture in women, but not in men. Further
studies specifically examining the interaction between BMI and sex on hip fracture
risk are needed. Studies included in this review were large and methodologically rigorous
prospective studies and indicate that BMI is a significant prognostic factor for hip
fracture, but one that may not be independent of BMD.
