Adherence to drugs that prevent cardiovascular disease: meta-analysis on 376,162 patients.

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.