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Bisphosphonate therapy increases atypical femur fracture risk in Asian women
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The relative risk for atypical femur fracture is more than sixfold higher among Asian woman initiating bisphosphonate therapy vs. white women, according to research in Bone.
Joan C. Lo, MD, of Kaiser Permanente Northern California, and colleagues analyzed data from 48,390 women aged at least 50 years who initiated oral bisphosphonate therapy between 2002 and 2007 (65.3% white; 17.1% Asian; mean age, 70 years), using data from the Kaiser Permanente Northern California health care delivery system. Researchers followed patients for a mean of 7.7 years; 88.2% of participants had follow-up at least 5 years after bisphosphonate initiation. Most women in the cohort received alendronate (96.6%); most prescriptions were for a daily dose equivalent of 10 mg per day (86.2%). Researchers examined the risk for atypical femur fracture in Asian women compared with white women, adjusting for differences in bisphosphonate exposure and other risk factors.
Within the cohort, 68 women (41 Asian) experienced atypical femur fracture. The rate of atypical femur fracture was 18.7 per 100,000 person-years overall; 7.2 per 100,000 person-years for white women and 64.2 per 100,000 person-years for Asian women. Asian women were more likely to have longer bisphosphonate treatment duration compared with whites (mean of 3.8 years vs. 2.7 years).
Comparing Asian women with white women, the age-adjusted HR for atypical femur fracture was 8.52 (95% CI, 4.86-14.94), and 6.57 (95% CI, 3.75-11.51) after adjusting for current and prior bisphosphonate therapy.
“Our analyses, conducted within a large, multiethnic cohort of women initiating [bisphosphonate therapy], demonstrates that Asians are at substantially higher risk for [atypical femur fracture] when compared to women of white race,” the researchers wrote. “This association was not substantially modified by putative clinical risk factors and remained after adjusting for differences in [bisphosphonate therapy] exposure.” – by Regina Schaffer
Disclosure: Lo reports receiving prior research funding from Amgen and current funding from Sanofi. Please see the full study for a list of all other authors’ relevant financial disclosures.
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