Nonadherence Is Common in Patients With Apparent Resistant Hypertension: A Systematic Review and Meta-analysis

Background The prevalence of medication nonadherence in the setting of resistant hypertension (RH) varies from 5% to 80% in the published literature. The aim of this systematic review was to establish the overall prevalence of nonadherence and evaluate the effect of the method of assessment on this estimate. Methods MEDLINE, EMBASE, Cochrane, CINAHL, and Web of Science (database inception to November 2020) were searched for relevant articles. We included studies including adults with a diagnosis of RH, with some measure of adherence. Details about the method of adherence assessment were independently extracted by 2 reviewers. Pooled analysis was performed using the random effects model and heterogeneity was explored with metaregression and subgroup analyses. The main outcome measured was the pooled prevalence of nonadherence and the prevalence using direct and indirect methods of assessment. Results Forty-two studies comprising 71,353 patients were included. The pooled prevalence of nonadherence was 37% (95% confidence interval [CI] 27%-47%) and lower for indirect methods (20%, 95% CI 11%-35%), than for direct methods (46%, 95% CI 40%-52%). The study-level metaregression suggested younger age and recent publication year as potential factors contributing to the heterogeneity. Conclusions Indirect methods (pill counts or questionnaires) are insufficient for diagnosis of nonadherence, and report less than half the rates as direct methods (direct observed therapy or urine assays). The overall prevalence of nonadherence in apparent treatment RH is extremely high and necessitates a thorough evaluation of nonadherence in this setting.