Adherence to chronic cardiovascular therapies: persistence over the years and dose coverage

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT * Cardiovascular diseases are the major cause of premature death in most Western countries. * Drug treatment, along with diet and lifestyle changes, is the mainstay of prevention and is effective provided that it is maintained over time. * Treatments with antihypertensives or lipid-lowering agents are known to be affected by a high rate of early withdrawal. WHAT THIS STUDY ADDS Four classes of drugs for cardiovascular prevention were studied, and they showed different patterns of use: * Poor adherence to antihypertensive and lipid-lowering therapies, probably due to poor perception of risk and a too early start of pharmacological treatment. * Higher adherence to oral hypoglycaemic agents and nitrates, which are used in conditions where disease awareness and the consequences of stopping medication favour compliance. AIM To evaluate adherence to chronic cardiovascular drug treatments, in terms of long-term persistence and dose coverage. METHODS General practice prescription data of antihypertensives, lipid-lowering agents, oral hypoglycaemic agents and nitrates were collected over a 5-year period (1998-2002) in a Northern Italian district (Ravenna, 350 000 inhabitants). We selected subjects (>40 years) receiving at least one prescription of the above drugs in December 1999. For each patient, we documented the regimen at the time of selection and evaluated adherence to treatment during the following 3 years in terms of persistence (at least one prescription per year) and daily coverage (recipients of an amount of medication consistent with daily treatment). RESULTS Fewer than 10% of the 32 068 selected subjects were naive to treatment. Antihypertensives were the most represented therapeutic category. Among patients already on treatment in December 1999, persistence was virtually complete, whereas >40% of naive patients withdrew within 1 year, except for nitrates. The rates of coverage were always much lower than the corresponding values of persistence. Coverage was significantly higher in older patients (chi(2) for trend 69.41; P < 0.001), males (odds ratio 1.30; 95% confidence interval 1.25, 1.36) and users receiving more than one therapeutic category. CONCLUSIONS Lack of adherence to chronic cardiovascular treatments represents an important matter of concern: although most people continued treatment over the years, less than 50% received an amount of drugs consistent with daily treatment, thus jeopardizing the proved beneficial effects of available medications.