Association Between Persistence with Statin Therapy and Reduction in Low-Density Lipoprotein Cholesterol Level: Analysis of Real-Life Data from Community Settings

Abstract

To validate the use of drug dispensing data as a measure of drug exposure and to quantify the association between persistence with statin therapy and low-density lipoprotein cholesterol (LDL) levels using real-life community data. Retrospective, population-based cohort study. Maccabi Healthcare Services (MHS) database, which contains linked prescription drug information, hospitalization records, and laboratory test results of 2million members of the second largest health organization in Israel. A total of 87,219 primary prevention patients and 15,139 secondary prevention patients who were MHS members and who started statin therapy between 1998 and 2008. Baseline and follow-up LDL levels were documented from 3months before the date of first dispensed statin (index date) to 6months afterward. Persistence was assessed by proportion of days covered (PDC) with statins during the follow-up period. Over the follow-up period, significant (p<0.001) reductions in LDL levels of 54, 33, and 13mg/dl were noted among highly persistent (PDC≥80%), moderately persistent (34%≤PDC<79%), and poorly persistent statins users (PDC≤33%), respectively. The reduction was observed as early as 2-3weeks after therapy initiation. In a multivariable model controlling for baseline LDL level and traditional coronary heart disease risk factors (diabetes mellitus, hypertension), high persistence with statin therapy was associated with a 27% and 25% decrement in LDL level among the primary and secondary prevention cohorts, respectively. Similarly, a higher proportion of the persistent statins users reached their target LDL level within the study follow-up period: 80% and 58% among primary and secondary prevention cohorts, respectively, compared with only 28% and 17%, respectively, among poorly persistent patients. In this observational population-based study, calculated PDC with statins during study follow-up was strongly associated with drug effect of LDL level reduction. The results agree with previous estimates of statin efficacy from randomized clinical trials, supporting the validity of using PDC methods as a measure of drug exposure.