Association of Statin Adherence With Mortality in Patients With Atherosclerotic Cardiovascular Disease

Abstract

Importance: Statins decrease mortality in those with atherosclerotic cardiovascular disease (ASCVD), but statin adherence remains suboptimal.

Objective: To determine the association between statin adherence and mortality in patients with ASCVD who have stable statin prescriptions.

Design, setting, and participants: This retrospective cohort analysis included patients who were between ages 21 and 85 years and had 1 or more International Classification of Diseases, Ninth Revision, Clinical Modification codes for ASCVD on 2 or more dates in the previous 2 years without intensity changes to their statin prescription who were treated within the Veterans Affairs Health System between January 1, 2013, and April 2014.

Exposures: Statin adherence was defined by the medication possession ratio (MPR). Adherence levels were categorized as an MPR of less than 50%, 50% to 69%, 70% to 89%, and 90% or greater. For dichotomous analyses, adherence was defined as an MPR of 80% or greater.

Main outcomes and measures: The primary outcome was death of all causes adjusted for demographic and clinical characteristics, as well as adherence to other cardiac medications.

Results: Of 347 104 eligible adults with ASCVD who had stable statin prescriptions, 5472 (1.6%) were women, 284 150 (81.9%) were white, 36 208 (10.4%) were African American, 16 323 (4.7%) were Hispanic, 4093 (1.2%) were Pacific Islander, 1293 (0.4%) were Native American, 1145 (0.3%) were Asian, and 1794 (0.5%) were other races. Patients taking moderate-intensity statin therapy were more adherent than patients taking high-intensity statin therapy (odds ratio [OR], 1.18; 95% CI, 1.16-1.20). Women were less adherent (OR, 0.89; 95% CI, 0.84-0.94), as were minority groups. Younger and older patients were less likely to be adherent compared with adults aged 65 to 74 years. During a mean (SD) of 2.9 (0.8) years of follow-up, there were 85 930 deaths (24.8%). Compared with the most adherent patients (MPR ≥ 90%), patients with an MPR of less than 50% had a hazard ratio (HR; adjusted for clinical characteristics and adherence to other cardiac medications) of 1.30 (95% CI, 1.27-1.34), those with an MPR of 50% to 69% had an HR of 1.21 (95% CI, 1.18-1.24), and those with an MPR of 70% to 89% had an HR of 1.08 (95% CI, 1.06-1.09).

Conclusions and relevance: Using a national sample of Veterans Affairs patients with ASCVD, we found that a low adherence to statin therapy was associated with a greater risk of dying. Women, minorities, younger adults, and older adults were less likely to adhere to statins. Our findings underscore the importance of finding methods to improve adherence.

Figure.. Survival Curves by Statin Adherence Level as Defined by Medication Possession Ratios (MPRs)

Plotted values include point estimates and 95% confidence intervals. There is a dose-response association between adherence and survival, with the greatest survival among the most adherent patients.