The Association of Hip Circumference With Incident Hip Fracture in a Cohort of Postmenopausal Women: The Iowa Women's Health Study

Purpose: As the mean age of the U.S. population increases, the public health burden of osteoporotic fractures is expected to increase. This study prospectively examined the independent association of hip circumference with hip fracture. Methods: The prospective association of hip circumference and hip fracture was examined in a cohort of 30,652 postmenopausal women. Results: Compared with the lowest quintile, successive quintiles of hip circumference were associated with a reduced hazard (i.e., hazard ratio [HR]) of hip fracture over 18 years of follow-up (HRs = 1.00, 0.78, 0.74, 0.76, 0.69, p for trend = 0.0015) after adjusting for age. Controlling for waist, this association persisted (HRs = 1.00, 0.78, 0.73, 0.72, 0.54, p for trend = 0.0006). When additionally controlling for body mass index (BMI), we found that the association of hip fracture with hip circumference was attenuated to the null whereas the association with successive quintiles of BMI remained significant and inverse (HRs = 1.00, 0.55, 0.45, 0.40, 0.35, p for trend <0.0001). Conclusions: Although hip circumference has a strong inverse association with risk of hip fracture, this association was not independent of BMI. These results suggest that, in the prediction of hip fracture risk, overall body size may be more important than body composition of the femoral-gluteal region.