Statin adherence and LDL cholesterol levels. Should we assess adherence prior to statin upgrade?

Adherence to statin therapy has been shown to be suboptimal. In statin-treated patients with residual elevated low density lipoprotein cholesterol (LDL-C) levels the physician must decide whether to switch to a more potent statin or try and achieve better adherence. We examined the association between adherence and LDL-C within low, moderate and high intensity statin groups in a "real world" setting.

We assessed annual adherence by the mean MPR (Medication Possession Ratio = number of purchased/prescribed daily doses) in unselected patient group. Statins were stratified (ACC/AHA Guideline) into low, moderate and high intensity groups. The impact of adherence on LDL levels was assessed by LOESS (locally weighted scatter plot smoothing).

Out of 1183 patients 173 (14.6%) were treated with low, 923 (78.0%) with moderate and 87 (7.4%) with high intensity statins. Statin intensity was inversely associated with adherence (MPR 77±21, 73±22 and 69±21% for low, moderate and high intensity respectively, p=0.018). Non-adjusted LDL levels decreased with higher adherence: a 10% adherence increase resulted in LDL decrease of 3.5, 5.8 and 7.1mg/dL in low, moderate and high intensity groups. Analysis of the adherence effect on LDL levels adjusted for age, DM and ischemic heart disease showed that MPR above 80% was associated with an additional decrease in LDL levels only in the high intensity group.

Increased adherence to statins beyond an MPR of 80% improves LDL levels only among patients given high intensity therapy. Switching from lower to higher intensity therapy may be more effective than further efforts to increase adherence.