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

To evaluate adherence to chronic cardiovascular drug treatments, in terms of long-term persistence and dose coverage.

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).

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.

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.