Adherence to medications remains poor despite numerous efforts to identify and intervene upon nonadherence. One potential explanation is the limited focus of many interventions on one barrier. Little is known about the prevalence and impact of having multiple barriers in contemporary practice. Our objective was to quantify adherence barriers for patients with poorly controlled cardiometabolic condition, identify patient characteristics associated with having multiple barriers, and determine its impact on adherence. We used a linked electronic health records and insurer claims dataset from a large health system from a recent pragmatic trial. Barriers to medication taking before the start of the intervention were elicited by clinical pharmacists using structured interviews. We used multivariable modified Poisson regression models to examine the association between patient factors and multiple barriers and multivariable linear regression to evaluate the relation between multiple barriers and claims-based adherence. Of the 1,069 patients (mean: 61 years of age) in this study, 25.1% had multiple barriers to adherence; the most common co-occurring barriers were forgetfulness and health beliefs (31%, n = 268). Patients with multiple barriers were more likely to be non-white (relative risk [RR] 1.57, 95% confidence interval [CI] 1.21 to 1.74), be single/unpartnered (RR 1.36, 95% CI 1.06 to 1.74), use tobacco (RR 1.54, 95% CI 1.13 to 2.11), and have poor glycemic control (RR 1.77, 95% CI 1.31 to 2.39) versus those with 0 or 1 barrier. Each additional barrier worsened average adherence by 3.1% (95% CI -4.6%, -1.5%). In conclusion, >25% of nonadherent patients present with multiple barriers to optimal use, leading to meaningful differences in adherence. These findings should inform quality improvement interventions aimed at nonadherence.
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