Eligible for inclusion were studies that measured adherence to drugs for the prevention of coronary heart disease in patients with and without a diagnosis of coronary heart disease. Drug classes included aspirin, angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, beta-blockers, calcium channel blockers, thiazide diuretics, and statins. Studies had to measure adherence using pharmacy prescription refill data and report the number of patients obtaining drugs for at least 75% of days over a defined period of time. Studies were also required to report the method of payment for medication (self-payment, state payment, or assisted payment).
Included studies were conducted in the USA, Canada, Australia, and Europe from 1998 up to 2010. The mean age of included patients was 65 years; 49% were male. Approximately half of the studies were of patients without a history of coronary heart disease (patients being treated for hypertension or high cholesterol) who received drugs for the primary prevention of coronary heart disease. The remaining studies were of patients with a diagnosis of coronary heart disease (patients with a history of myocardial infarction, ischaemic heart disease, angina, percutaneous coronary intervention, or coronary artery bypass grafting) who received drugs for the secondary prevention of recurrent events.
The method of payment in 17 studies was assisted payment; in two studies it was state payment, and in one study it was self-payment.
The authors did not state how many reviewers screened studies for inclusion.