Fracture outcome of non-adherence to osteoporosis medications among older women

Osteoporosis medications have been shown to reduce fracture risk. However, relatively few studies have examined the role of medication adherence in fracture prevention. The goal of this study was to examine associations between adherence and fracture-related hospitalization risk among older women using osteoporosis medications. The prescription refill patterns of 8,277 older women enrolled in Pennsylvania's Pharmaceutical Assistance Contract for the Elderly (PACE) Program who used osteoporosis medications in 2003 were evaluated. Two medication adherence indicators were computed: the Proportion of Days Covered (PDC) and persistence. PDC represents the proportion of days covered by at least one medication within a therapeutic class, and persistence indicates whether the patient continued refilling prescriptions throughout the observation period. Multivariate logistic regression was used to examine the relationship between osteoporosis medication adherence and hospitalization for fracture in 2003 while controlling for demographics, comorbidity, average PDC across other chronic therapeutic classes, and recency of osteoporosis therapy initiation. Relative to full adherence (PDC≥80%), low osteoporosis medication adherence (PDC<60%) was associated with increased risk of hospitalization for fracture among new users (OR=1.91, P=0.06). Non-persistence to osteoporosis medication was associated with increased risk of fracture-related hospitalization among long-term users (OR=1.71, P=0.02). Charlson comorbidity (OR=1.21, P<0.0001) and average PDC level of other therapeutic classes (OR=0.14, P=0.0006) were also significant predictors of hospitalization for fracture. These results indicate that both general medication non-adherence and osteoporosis medication-specific non-adherence are associated with increased fracture risk. The findings also suggest that the benefits of osteoporosis medication adherence may be dependent on therapy duration.