Risk of refracture associated with compliance and persistence with bisphosphonate therapy in Taiwan

Bisphosphonates have been used for the treatment of postmenopausal osteoporosis since the early 1990s and studies show that compliant patients experience a lower fracture rate. This cohort study showed that the compliance of Taiwanese patients was poor and the refracture risk was related to compliance with bisphosphonate therapy. Introduction: Bisphosphonates are potent inhibitors of osteoclast activity, and reduce bone turnover by inhibiting bone resorption. According to Taiwanese reimbursement guidelines, patients with osteoporosis-related fractures are eligible for bisphosphonate treatment. This study aimed to elucidate the relationship of refracture risk with compliance/persistence with bisphosphonate therapy in Taiwan. Methods: This was a retrospective, administrative, database analysis measuring the adherence status and impact of poor adherence to bisphosphonate therapy in Taiwan. Study data derived from the National Health Insurance Research Database (NHIRD) were used to assemble a cohort of all osteoporosis patients who initiated bisphosphonate treatment between January 1, 2004, and December 31, 2005. Patients were followed until death, end of registration in NHIRD, or end of study period (December 31, 2006), whichever occurred first. Compliance was calculated as medication possession ratio (MPR; sum of days of supply of osteoporosis medications divided by follow-up duration). Results: The refracture rates for osteoporosis patients were 5.15 %, 7.36 %, and 8.49 % in the first, second, and third year, respectively, and were significantly lower for patients with >80 % compliance than with <80 % compliance (p < 0.05). Nearly 50 % patients were noncompliant (MPR < 80 %) at 3 months, and only around 30 % patients were adherent at 1 year. Refracture risk increased with MPR < 80 %, age, and co-morbidities like diabetes mellitus or dementia. Patients with concomitant statin medication had significantly lower refracture risk. Conclusions: The compliance of Taiwanese patients with osteoporosis medication is poor, and refracture risk is related to compliance with bisphosphonate therapy.