Time trends in oral bisphosphonate initiation in Ontario, Canada over 20 years reflect drug policy and healthcare delivery changes.

Characteristics of patients starting oral bisphosphonate therapy changed over time, reflecting trends in osteoporosis management (e.g., new drugs to market), and general healthcare delivery (e.g., benzodiazepine use declined, statin use increased). When designing studies that examine osteoporosis drug effects, potential time-related biases must be considered.
Introduction: To describe the type of oral bisphosphonate initiated and characteristics of patients starting oral bisphosphonate therapy over time.
Methods: We identified community-dwelling older adults (ages ≥ 66 years) initiating oral bisphosphonate therapy from April 1996 to March 2016 (1996 to 2015 fiscal years) using healthcare administrative data in Ontario. Patients with conditions other than osteoporosis that may impact bisphosphonate prescribing were excluded. The bisphosphonate initiated and patient characteristics were summarized by fiscal year and stratified by sex.
Results: We identified 560,817 eligible patients (81% women). Most patients initiated cyclical etidronate from 1996 until 2005, and then weekly regimens became dominant. In 2008, risedronate became the main oral bisphosphonate (46% risedronate, 43% alendronate, 11% etidronate); with its use increasing after availability of monthly and delayed-release risedronate formulations. In 2015, 71% of patients started risedronate, 28% started alendronate, and less than 2% started etidronate. Characteristics of patients changed over time, reflecting changes in osteoporosis management and general healthcare delivery. Over time, a larger proportion of men (9% to 28%) and patients with diabetes (women 10% to 17%, men 14% to 22%) initiated therapy; benzodiazepine (women 22% to 13%, men 20% to 10%) and estrogen-based hormone replacement therapy (12% to 15% of women 1996-2002 to 3% since 2008) decreased, while statin use increased (women 15% to 39%, men 14% to 52%).
Conclusions: The characteristics of patients starting oral bisphosphonate therapy have changed over time. Consideration must be given to these time trends when designing studies that examine osteoporosis drug effects.