ABSTRACT: BACKGROUND: Prior observational studies have shown an association between bisphosphonate adherence and fewer fractures. It is unclear if such studies reflect pharmacologic benefits or behavioral attributes, i.e. the healthy adherer effect. OBJECTIVE: To examine the association of therapy adherence and fracture risk among patients initiating therapies hypothesized to be favorable, unfavorable, or neutral toward fracture risk so as to evaluate for a healthy adherer effect. METHODS: In this observational study, we identified patients within Medicare 2006-09 data who initiated any of three medication groups within nine months after an osteoporotic fracture: 1) oral bisphosphonates (n = 2507), 2) selective serotonin reuptake inhibitors (SSRI) (n=2420), or 3) angiotensin converting enzyme inhibitor, or calcium channel blocker (ACE/CCB) (n=2178). Cox regression analysis, adjusting for covariates, was used to compare fracture rates at the hip and major osteoporotic fracture sites including hip, clinical vertebral, humerus, and wrist during follow-up comparing patients with high adherence versus low adherence within each medication group. RESULTS: There were few baseline differences between those who had high adherence versus lower adherence. High adherence with bisphosphonates decreased fracture risk at both hip (hazard ratio (HR) =0.53, 95% CI 0.32-0.96) and major fracture sites (HR = 0.61, 0.45-0.80). High adherence with SSRIs suggested increased fracture risk at both hip (HR = 1.58, 0.97-2.57) and major fracture sites (HR=1.32, 0.96-1.83). High adherence with ACE/CCBs was neutral toward fracture risk at both hip (HR = 1.27, 0.67-2.41) and major fracture sites (HR = 1.00, 0.67-1.49). CONCLUSION: In this observational cohort of older individuals, the association between medication adherence and fracture risk differed by medication exposure, suggesting a limited role for the healthy adherer effect in observational studies of osteoporosis medications.
Arthritis care & research. 06/2012;