Aims To determine the patterns and predictors of long-term adherence to statin therapy in all patients with diabetes in the community setting.
Methods We retrospectively studied patients with diabetes who were resident in Tayside, Scotland from 1 January 1989 to 31 May 2003 and initiated statin treatment during that time. The main outcome measure was percentage of days covered (PDC) by a statin, calculated at regular intervals. Predictors of suboptimal adherence (PDC < 80%) were identified using generalized linear models for repeated measures.
Results Six thousand four hundred and sixty-two patients were included in the study. In the first year, the mean PDC was 87, 61% in the first and second quarter, respectively, and 65% after 13 years. Less than 50% of patients maintained a PDC of > 80% after 13 years. Predictors of poor long-term adherence were younger age, higher HbA1c, no history of smoking, no cardiovascular morbidity at baseline and occurrence of cardiovascular disease after statin commencement.
Conclusions This study suggests that barriers to long-term adherence to statins tend to arise early on in the therapeutic course. In general, long-term adherence is poor in patients with diabetes, especially among those with few other cardiovascular risk factors.