A Population-Based Study of the Effectiveness of Bisphosphonates at Reducing Hip Fractures among High Risk Women

The availability of the Medicare Part D benefit presents an opportunity for improved pharmacologic management of patients with chronic conditions. Using the Medicare administrative claims files from the Chronic Condition Data Warehouse (CCW), we sought to determine the prevalence of bisphosphonate use among female Medicare beneficiaries with osteoporosis, and whether use reduced the risk of hip fracture. The study population included a 20% sample of female Medicare beneficiaries 65 and older who had fee-for-service (FFS) Part A and B and Part D coverage at least through the end of 2006. A cohort of Medicare beneficiaries at high risk for fractures (those with an osteoporosis diagnosis), and a lower risk comparison group was selected for study (older women without any common chronic condition). The population was followed from 2006 through the end of 2008, or until censored due to death or disenrollment from FFS Medicare or the Part D benefit. The cohort was examined for bisphosphonate exposure. The primary outcome of interest was a hospitalization for hip fracture. Rates of hip fracture by risk and drug use were calculated as well as the time to fracture in the different strata. During the observation period, 1.3% of all women in the study had at least one hospitalization for hip fracture. Hip fracture rates were significantly lower for the high-risk subpopulation exposed to bisphosphonates. Sixty-eight percent of women in the high risk group received some form of bisphosphonate, compared to 13 percent of the lower risk group. Among bisphosphonate users, alendronate was most commonly used.