Association between persistence with statin therapy and reduction in low-density lipoprotein cholesterol level: analysis of real-life data from community settings.
STUDY OBJECTIVES
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.


DESIGN
Retrospective, population-based cohort study.


DATA SOURCE
Maccabi Healthcare Services (MHS) database, which contains linked prescription drug information, hospitalization records, and laboratory test results of 2 million members of the second largest health organization in Israel.


PATIENTS
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.


MEASUREMENTS AND MAIN RESULTS
Baseline and follow-up LDL levels were documented from 3 months before the date of first dispensed statin (index date) to 6 months 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 13 mg/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 2-3 weeks 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.


CONCLUSIONS
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.