Is the high-risk strategy to prevent cardiovascular disease equitable? A pharmacoepidemiological cohort study

BACKGROUND Statins are increasingly prescribed to prevent cardiovascular disease (CVD) in asymptomatic individuals. Yet, it is unknown whether those at higher CVD risk - i.e. individuals in lower socio-economic position (SEP) - are adequately reached by this high-risk strategy. We aimed to examine whether the Danish implementation of the strategy to prevent cardiovascular disease (CVD) by initiating statin (HMG-CoA reductase inhibitor) therapy in high-risk individuals is equitable across socioeconomic groups. METHODS DESIGN Cohort study. SETTING AND PARTICIPANTS Applying individual-level nationwide register information on socio-demographics, dispensed prescription drugs and hospital discharges, all Danish citizens aged 20+ without previous register-markers of CVD, diabetes or statin therapy were followed during 2002-2006 for first occurrence of myocardial infarction (MI) and a dispensed statin prescription (N = 3.3 mill). MAIN OUTCOME MEASURES Stratified by gender, 5-year age-groups and socioeconomic position (SEP), incidence of MI was applied as a proxy for statin need. Need-standardized statin incidence rates were calculated, applying MI incidence rate ratios (IRR) as need-weights to adjust for unequal needs across SEP.Horizontal equity in initiating statin therapy was tested by means of Poisson regression analysis. Applying the need-standardized statin parameters and the lowest SEP-group as reference, a need-standardized statin IRR > 1 translates into horizontal inequity favouring the higher SEP-groups. RESULTS MI incidence decreased with increasing SEP without a parallel trend in incidence of statin therapy. According to the regression analyses, the need-standardized statin incidence increased in men aged 40-64 by 17%, IRR 1.17 (95% CI: 1.14-1.19) with each increase in income quintile. In women the proportion was 23%, IRR 1.23 (1.16-1.29). An analogous pattern was seen applying education as SEP indicator and among subjects aged 65-84. CONCLUSION The high-risk strategy to prevent CVD by initiating statin therapy seems to be inequitable, reaching primarily high-risk subjects in lower risk SEP-groups.