Objective: To assess the long-term predictive usefulness of radiographic absorptiometry measurements of phalangeal bone density for hip fracture risk.
Methods: Participants were members of the First National Health and Nutrition Examination Survey Epidemiologic Follow Up Study cohort. Subjects were followed up for a maximum of 16 years. The First National Health and Nutrition Examination Survey data were obtained from a nationally representative sample of non-institutionalized civilians. A cohort of 3481 white and black subjects (1559 white women) aged 45 through 74 years at baseline (1971-1975) were observed through 1987. Ninety-eight percent of the original cohort completed the study. Hospital records and death certificates were used to identify a total of 72 hip fracture cases. Phalangeal bone density at baseline was measured using photodensitometry (PD), and later reanalyzed by radiographic absorptiometry (RA), a newer, more sophisticated technique.
Results: Results were evaluated to determine the relative risk for hip fracture per 1-SD decrease in bone density, after controlling for age at baseline, race, gender, weight, and previous fractures. Both RA and PD measurements showed a significant inverse relationship to hip fracture risk, with RA density measurements showing a slightly higher adjusted relative risk per 1-SD density decrease than PD measurements. For RA bone density, the relative risk for all subjects was 1.81 (95% confidence interval, 1.34-2.44) compared with 1.57 (95% confidence interval, 1.19-2.07) for PD bone density after adjusting for age at baseline, race, gender, weight, and previous fractures. Results for white women were essentially the same as those for all subjects for RA bone density and PD bone density.
Conclusions: Phalangeal bone density determined from standard hand x-ray films is a significant predictor of future hip fracture risk. Availability of a valid method to assess fracture risk using conventional radiographs will expand the ability to identify individuals with osteoporosis.