Cost and Consequences of Nonadherence With Oral Bisphosphonate Therapy

Background: Adherence to osteoporosis treatment remains poor despite available treatments and physician and patient education. This study aims to determine the effect of low adherence in real-world data. Objective: To examine the association between adherence with oral bisphosphonate therapy and fracture risk as well as health care resource utilization. Methods: Women included in this retrospective analysis were 55 years or older and had started oral bisphosphonate therapy between 2005 and 2011 in a large not-for-profit health care center in Israel. Adherence to therapy was measured by the medication possession ratio (MPR) during the first year from therapy initiation. Patients with MPR lower than 70% were considered nonadherent. Study outcomes were osteoporotic fracture events and health care utilization (including physician visits and hospitalizations) during the second year from therapy initiation. Results: Among the 17 770 women included in the analysis (mean age = 66.5 years; SD = ±8.3 years), 48.9% were nonadherent to therapy during the first year of treatment. Osteoporotic fracture risks during the second year among adherent and nonadherent patients were 2.1% and 2.5%, respectively (P = 0.1). When analysis was limited to patients 75 years or older, nonadherence with bisphosphonates was associated with an adjusted odds ratio of 1.49 (95% CI = 1.08-2.04) for osteoporotic fractures compared with adherent patients. Nonadherent patients had 13.4% higher medical costs than their adherent counterparts among patients 75 years and older (P = 0.002). Conclusions: In patients 75 years and older, nonadherence with oral bisphosphonates can be associated with significantly greater short-term risk of osteoporotic fractures and higher utilization of health care services.