The contribution of hip fracture to risk of subsequent fractures: data from two longitudinal studies.

Background: The contribution of hip fracture to the risk of subsequent fractures is unclear.
Methods: Data from the Baltimore Hip Studies and the Established Populations for Epidemiologic Studies of the Elderly (EPESE) were used. Baltimore subjects enrolled at the time of hip fracture ( n=549) and EPESE subjects without previous fractures at baseline ( n=10,680) were followed for 2-10 years. Self-reported nonhip skeletal fracture was the outcome, and hip fracture was a time-varying covariate in a survival analysis stratified by study site. The model was adjusted for race, sex, age, BMI, stroke, cancer, difficulty walking across a room, dependence in grooming, dependence in transferring, and cognitive impairment.
Results: The rate of all subsequent self-reported fractures after hip fracture was 10.4 fractures/100 person-years. The unadjusted hazard of nonhip skeletal fracture was 2.52 (95% confidence interval 2.05 to 3.12) for subjects with hip fracture compared with subjects without; when adjusted for other known fracture risk factors the hazard ratio was 1.62 (1.30 to 2.02). Men and women had a similar relative risk increase. The increased risk of secondary fracture after hip fracture persisted over time.
Conclusions: A hip fracture is associated with a 2.5-fold increased risk of subsequent fracture, which is not entirely explained by prefracture risk factors. Careful attention to secondary prevention is warranted in these patients.