Association between statin adherence and cholesterol level reduction from baseline in a veteran population.

STUDY OBJECTIVE

To investigate the association between statin adherence and changes in lipid panel outcomes from baseline in a veteran population.

DESIGN

Retrospective cohort study using multiple linear regression models.

SETTING

Veterans Affairs health care system within the Veterans Integrated Service Network 22, a network of Veterans Affairs facilities in the southwest region of the United States that includes Los Angeles, San Diego, Loma Linda, and Long Beach, California, and Las Vegas, Nevada, with an enrollment of approximately 1.4 million veterans.

PATIENTS

A total of 5365 patients who were new statin users between December 1, 2006, and November 30, 2007; 2674 patients were in the adherent group and 2691 were in the nonadherent group.

MEASUREMENTS AND MAIN RESULTS

Adherence was determined by the medication possession ratio. Patients were categorized as adherent if the medication possession ratio at follow-up was 0.80 or more. Adherent patients exhibited significant differences in baseline demographic and clinical characteristics than nonadherent patients in our study sample. Baseline laboratory values for adherent patients were significantly lower for low-density lipoprotein cholesterol (LDL), high-density lipoprotein cholesterol (HDL), non-high-density lipoprotein cholesterol (non-HDL), and total cholesterol levels. The primary outcome was change in LDL level from baseline at 12 months. Secondary outcomes were changes in non-HDL and total cholesterol levels from baseline at 12 months. Independent variables controlled for in the multiple linear regression included age, sex, body mass index, race-ethnicity, baseline lipid panel (LDL, HDL, total cholesterol, and triglycerides), statin copayment status, income quintile (according to ZIP code median household income), baseline medication count, statin prescribed, and comorbidities. Multiple linear regression revealed that adherent patients demonstrated significantly greater reductions in LDL of 20.98 mg/dl versus nonadherent patients (p<0.0001). Adherent patients similarly demonstrated larger reductions of 24.31 mg/dl in non-HDL and 24.06 mg/dl in total cholesterol versus nonadherent patients (p<0.0001 for both comparisons).

CONCLUSION

Patients adherent to statin therapy had significant associations with clinically relevant reductions in LDL, non-HDL, and total cholesterol from baseline at 12 months compared with nonadherent patients when controlling for potential confounders. Adherence to statin therapy may have important consequences in decreasing clinical outcomes such as myocardial infarctions, strokes, and mortality due to large reductions in lipid panel outcomes from baseline at 12 months.