AIM: We sought to determine the extent to which higher lean and fat mass as measured by dual X-ray absorptiometry in older adults with frailty are related to total hip bone mass density (BMD) index and the rate of hip fractures.

METHODS: The data are from the Women's Health Initiative Observational Study. We identified 872 participants aged > /=65 years with body composition measures and positive frailty. Frailty was determined using modified Fried's criteria. Linear and Cox regressions were used to model study outcomes.

RESULTS: During the follow-up period, 5.6% patients (n = 49) had sustained a hip fracture. Body composition indexes were associated with total hip BMD (P < 0.001 for all). In models adjusted for age, ethnicity, smoking, history of fractures, recurrent falls, number of frailty criteria and corresponding lean mass, the hazard ratio for hip fracture per 1 kg/m2 increase in fat mass was 0.73 (95% confidence interval 0.60-0.88) for appendicular compartment, 0.76 (95% confidence interval 0.65-0.89) for trunk and 0.84 (95% confidence interval 0.77-0.93) for whole-body fat mass. The hazard ratio for hip fracture per 1 kg/m2 increase in appendicular lean mass was 0.63 (95% confidence interval 0.46-0.88). However, after final adjustment for total hip BMD, the only index that remained statistically significant was whole-body fat mass (P for trend = 0.04).

CONCLUSIONS: We showed that in frail older women, higher fat and lean mass was associated with reduced hip-fracture rates. Higher whole-body adiposity, however, was also associated with lower hip-fracture rate independent of total hip BMD. The present results confirm the importance of weight maintenance in frail populations.