BackgroundResistant hypertension is quite prevalent and a risk factor for cardiovascular events. Patients with suspected resistant hypertension undergo more screening intensity for secondary hypertension, despite some of them being non-adherent to prescribed pharmacotherapy. The prevalence of non-adherence in this setting varies from about 5 to 80% in the published literature. Apart from the wide range, the relation between method of assessment and prevalence is not well established. Our objective was to establish the overall prevalence of non-adherence in the apparent treatment resistant hypertension population, explore causes of heterogeneity, and evaluate the effect of the method of assessment on the estimate of non-adherence.MethodsWe performed a systematic review and meta-analysis. MEDLINE, EMBASE Classic+EMBASE, Cochrane, CINAHL, and Web of Science were searched for relevant articles. Details about the method of adherence assessment were extracted from each included article and grouped into direct and indirect. Pooled analysis was performed using the random effects model and heterogeneity was explored with metaregression and subgroup analyses.ResultsThe literature search yielded 1428 studies, of which 36 were included. The pooled prevalence of non-adherence was 35% (95% confidence interval 25 – 46 %). For indirect methods of adherence assessment, it was 25% (95% CI 15 – 39 %), whereas for direct methods of assessment, it was 44% (95% CI 32 – 57 %). Metaregression suggested gender, age, and time of publication as potential factors contributing to the heterogeneity.ConclusionsNon-adherence to pharmacotherapy is quite common in resistant hypertension, with the prevalence varying with the methods of assessment.Brief SummaryResistant hypertension is known to be a risk factor for cardiovascular events. These patients also undergo higher screening intensity for secondary hypertension. However, not all patients with apparent treatment resistant hypertension have true resistant hypertension, with some of them being non-adherent to prescribed pharmacotherapy. This systematic review aims to establish the overall prevalence of non-adherence in the apparent treatment resistant hypertension population and assess the relative contributions of non-adherence assessed with direct and indirect measures.