Adherence to treatment of primary osteoporosis and its association to fractures--the Swedish Adherence Register Analysis (SARA)

Abstract

Summary: Osteoporosis treatments reduce the risk of fractures. The objective of this study was to investigate adherence to treatment of osteoporosis and its association to fractures in Sweden. Adherence to treatment of osteoporosis in Sweden is poor, and time on treatment was found to be significantly associated with fracture incidence.

Introduction: The objective of this study was to estimate persistence and compliance to treatment of primary osteoporosis in Sweden. A second aim was to investigate the determinants of non-persistence and the association between adherence and fracture incidence.

Methods: Patients were identified through filled prescriptions for alendronate, risedronate, strontium ranelate, and raloxifene between 2005 and 2009 from the Swedish Prescribed Drug Register. Persistence was investigated using survival analysis. Medication possession ratio (MPR) was used to measure compliance in persistent patients. The outcome measure in the analysis of adherence and fracture incidence was hospitalized osteoporotic fractures.

Results: The final cohort consisted of 56,586 treatment-naïve patients (mean age 71, 86% women). A total of 51%, 35%, 25%, and 14% were still on treatment (switching allowed) after 1, 2, 3, and 4 years, respectively. Average MPR in persistent patients was 94.2% (CI(95) 94.2-94.3%). Compared with <1 month of therapy, treatment for 1 month to 1 year, 1 to 2 years, and 2 to 3 years was associated with a lower 3-year fracture incidence (HR 0.86, p = 0.091; HR 0.67, p < 0.001; and HR 0.59, p < 0.001, respectively). No significant relationship was identified between MPR and fracture risk.

Conclusions: Persistence to treatment of osteoporosis in Sweden is poor and approximately 50% of all treatment-naïve patients discontinue therapy within 1 year. Average refill compliance, estimated only while the patients were persistent, was found to be close to perfect. A strong association was identified between treatment persistence and fracture incidence, which calls for action to improve the current situation.