Bisphosphonate Drug Holiday and Fracture Risk: A Population-Based Cohort Study

Holidays from bisphosphonates (BPs) may help to prevent rare adverse events such as atypical femoral fractures, but may be appropriate only if risk of osteoporosis-related fractures does not increase. Our objective was to compare the incidence of osteoporosis-related fractures among women who had a BP holiday to those who continued to use BPs. This retrospective cohort study, conducted within four Kaiser Permanente integrated health system regions, included 39,502 women aged 45 years with 3 years exposure to BP. Participants with a BP holiday (12 months with no use) were compared to persistent (use with 50% adherence) and nonpersistent (use with <50% adherence) users for incident osteoporosis-related fractures. The BP holiday (n=11,497), nonpersistent user (n=10,882), and persistent user groups (n=17,123) were observed for 156,657 person-years. A total of 5199 osteoporosis-related fractures (including 1515 hip fractures and 2147 vertebral fractures) were observed. Compared to the persistent use group, there was a slight difference in overall osteoporosis-related fracture risk (HR 0.92; 95% CI, 0.84 to 0.99)and no difference in hip fracture risk (HR 0.95; 95% CI, 0.83 to 1.10) for the BP holiday group. A slight reduction in risk of vertebral fracture was observed (HR 0.83; 95% CI, 0.74 to 0.95). Compared to the nonpersistent user group, the BP holiday group was at decreased risk for osteoporosis-related fractures (HR 0.71; 95% CI, 0.65 to 0.79), vertebral fractures (HR 0.68; 95% CI, 0.59 to 0.78), and hip fractures (HR 0.59; 95% CI, 0.50 to 0.70). Women who undertake a BP holiday from BP of 12 months duration for any reason after 3 years of BP use do not appear to be at greater risk of osteoporosis-related fragility fracture, hip, or vertebral fractures compared to ongoing BP users. In our cohort, BP holiday remains a viable strategy for balancing the benefits and potential harms associated with long-term BP use. (c) 2018 American Society for Bone and Mineral Research.