title: Adherence to cardiovascular therapy: a meta-analysis of prevalence and clinical consequences.
abstract: OBJECTIVE
  The aim of this study was to determine the extent to which adherence to individual vascular medications, assessed by different methods, influences the absolute and relative risks (RRs) of cardiovascular disease (CVD) and all-cause mortality.
  
  
  RESULTS
  We performed a systematic review and meta-analysis of prospective epidemiological studies (cohort, nested case-control, or clinical trial) identified through electronic searches using MEDLINE, Web of Science, EMBASE, and Cochrane databases, involving adult populations (≥ 18 years old) and reporting risk estimates of cardiovascular medication adherence with any CVD (defined as any fatal or non-fatal coronary heart disease, stroke or sudden cardiac death) and/or all-cause mortality (defined as mortality from any cause) outcomes. Relative risks were combined using random-effects models. Forty-four unique prospective studies comprising 1 978 919 non-overlapping participants, with 135 627 CVD events and 94 126 cases of all-cause mortality. Overall, 60% (95% CI: 52-68%) of included participants had good adherence (adherence ≥ 80%) to cardiovascular medications. The RRs (95% CI) of development of CVD in those with good vs. poor (<80%) adherence were 0.85 (0.81-0.89) and 0.81 (0.76-0.86) for statins and antihypertensive medications, respectively. Corresponding RRs of all-cause mortality were 0.55 (0.46-0.67) and 0.71 (0.64-0.78) for good adherence to statins and antihypertensive agents. These associations remained consistent across subgroups representing different study characteristics. Estimated absolute risk differences for any CVD associated with poor medication adherence were 13 cases for any vascular medication, 9 cases for statins and 13 cases for antihypertensive agents, per 100 000 individuals per year.
  
  
  CONCLUSIONS
  A substantial proportion of people do not adhere adequately to cardiovascular medications, and the prevalence of suboptimal adherence is similar across all individual CVD medications. Absolute and relative risk assessments demonstrate that a considerable proportion of all CVD events (~9% in Europe) could be attributed to poor adherence to vascular medications alone, and that the level of optimal adherence confers a significant inverse association with subsequent adverse outcomes. Measures to enhance adherence to help maximize the potentials of effective cardiac therapies in the clinical setting are urgently required.
authors.affiliation: Department of Public Health and Primary Care, University of Cambridge, Cambridge CB1 8RN, UK.
authors.forename: Rajiv
authors.initials: R
authors.lastname: Chowdhury
authors.forename: Hassan
authors.initials: H
authors.lastname: Khan
authors.forename: Emma
authors.initials: E
authors.lastname: Heydon
authors.forename: Amir
authors.initials: A
authors.lastname: Shroufi
authors.forename: Saman
authors.initials: S
authors.lastname: Fahimi
authors.forename: Carmel
authors.initials: C
authors.lastname: Moore
authors.forename: Bruno
authors.initials: B
authors.lastname: Stricker
authors.forename: Shanthi
authors.initials: S
authors.lastname: Mendis
authors.forename: Albert
authors.initials: A
authors.lastname: Hofman
authors.forename: Jonathan
authors.initials: J
authors.lastname: Mant
authors.forename: Oscar H
authors.initials: OH
authors.lastname: Franco
mesh_terms: D000328:Adult; D000368:Aged; D002317:Cardiovascular Agents / Q000627:therapeutic use*; D002318:Cardiovascular Diseases / Q000188:drug therapy* / Q000401:mortality; D002423:Cause of Death; D004812:Epidemiologic Methods; D006801:Humans; D008875:Middle Aged; D055815:Young Adult; D016903:Drug Monitoring
chemical_list: D002317:Cardiovascular Agents
keywords: Cardiovascular disease; Medication adherence