Elsevier

The American Journal of Medicine

Volume 125, Issue 9, September 2012, Pages 882-887.e1
The American Journal of Medicine

Clinical research study
Adherence to Drugs That Prevent Cardiovascular Disease: Meta-analysis on 376,162 Patients

https://doi.org/10.1016/j.amjmed.2011.12.013Get rights and content

Abstract

Objective

Combination therapy, specifically with aspirin, cholesterol and blood pressure-lowering drugs, substantially reduces the risk of coronary heart disease, but the full preventive effect is only realized if treatment continues indefinitely. Our objective was to provide a summary estimate of adherence to drugs that prevent coronary heart disease, according to drug class and use in people who have had a myocardial infarction (secondary prevention) and people who have not (primary prevention).

Methods

A meta-analysis of data on 376,162 patients from 20 studies assessing adherence using prescription refill frequency for the following 7 drug classes was performed: aspirin, angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, beta-blockers, calcium-channel blockers, thiazides, and statins. Meta-regression was used to examine the effects of age, payment, and treatment duration.

Results

The summary estimate for adherence across all studies was 57% (95% confidence interval [CI], 50-64) after a median of 24 months. There were statistically significant differences in adherence between primary and secondary prevention: 50% (CI, 45-56) and 66% (CI, 56-75), respectively (P = .012). Adherence was lower for thiazides (42%) than for angiotensin receptor blockers (61%) in primary prevention (P = .02). There were no other statistically significant differences between any of the drug classes in primary or secondary prevention studies. Adherence decreased by 0.15% points/month (P = .07) and was unrelated to age or whether patients paid for their pills.

Conclusion

Adherence to preventive treatment is poor and little related to class of drug, suggesting that side effects are not the main cause. General, rather than class-specific, measures at improving adherence are needed.

Section snippets

Materials and Methods

We searched medical databases (PubMed) for studies that assessed the extent to which individuals remained on coronary heart disease preventive drug therapy over time. The search terms used were [adherence, persistence, compliance, or concordance] and [drug treatment, aspirin, angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, beta-blockers, calcium channel blockers, thiazide diuretics, or statin].

We included studies of patients with and without a diagnosis of coronary

Results

Table 1 shows details of the studies in the meta-analysis, which included data on 376,162 patients (mean age 64 years, 49% were male). Eleven studies were on patients without a history of coronary heart disease (eg, patients being treated for hypertension) who were receiving drugs for the primary prevention of coronary heart disease, and 9 studies were on patients with a diagnosis of coronary heart disease (eg, after a myocardial infarction) who were receiving drugs for the secondary prevention

Discussion

The results of this analysis show that approximately two thirds of patients with a history of coronary heart disease adhere to drugs prescribed to prevent a second coronary heart disease event and approximately half of those without coronary heart disease adhere to drugs prescribed to prevent a first event.

Previous reviews on adherence to cardiovascular preventive treatments were descriptive and did not combine results within or across studies to provide a quantitative summary of effect.31, 32

Conclusions

Our results show that approximately one third of patients who have had a myocardial infarction and approximately one half of those who have not had a myocardial infarction do not adhere to effective cardiovascular preventive treatment long-term. Adherence is not greatly dependent on the class of drug prescribed, suggesting that interventions to improve adherence need to be broadly applied.

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    Funding: None.

    Conflict of Interest: None.

    Authorship: All authors had access to the data and played a role in writing this manuscript.

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