Bisphosphonate use and hip fracture epidemiology: ecologic proof from the contrary

Alex Fisher¹, Jodie Martin², Wichat Srikusalanukul², Michael Davis^1
1Department of Geriatric Medicine, The Canberra Hospital, Canberra, ACT, Australia; ²Australian National University Medical School, Canberra, ACT, Australia

Aim: The objective of this article is to evaluate the relationship between the changes in prescriptions of antiosteoporotic drugs (mainly the rapid fall in the use of bisphosphonates [BPs]) and standardized hip fracture (HF) rates over the period 2005–2008 in the Australian Capital Territory (ACT).
Methods: Annual sex- and age-specific HF rates (per 100,000 population) were determined and standardized using the Australian 2006 population census. Data on the annual prescriptions of BPs (mainly alendronate and risedronate), strontium ranelate, and hormone replacement therapy were obtained from the Australian Pharmaceutical Benefits Scheme (PBS) and Repatriation Australian Pharmaceutical Benefits Scheme (RPBS) databases.
Results: In the ACT, the peak annual number of prescriptions for BPs was observed in 2006. Following reports linking osteonecrosis of the jaw with BP use, the number of BP prescriptions dropped by 14% in 2007–2008 compared with 2005, when the lowest HF rates were recorded. The reduction in BP prescriptions coincided with increased HF rates in females in 2007 (+22.6%) and in 2008 (+25.2%) compared with 2005; in males, HF incidence declined by 6.6% and 16.7%, respectively. The proportion of filled prescriptions for strontium ranelate, risedronate, and alendronate in 2007–2008 was 1:8.4:15.5, indicating that BPs were the dominant antiosteoporotic drugs. There was an inverse statistically significant relationship between the total annual number of BP prescriptions and standardized HF incidence rates for the 10-year period 1999–2008.
Conclusion: Although currently there is no clear understanding of factors contributing to changing HF epidemiology, the available evidence suggests that much of the decline in HF rates is due to the use of BPs. The fall in the use of BPs is associated with an increase in HF rates in females, indicating that BPs should still be considered the first-line medications for the prevention and treatment of osteoporosis. Our results need to be confirmed in other populations and countries.

Keywords: bisphosphonate use, hip fracture, epidemiology