Research on the association between SEP and statin adherence has mainly defined adherence through measures that reduce longitudinal medication-taking behavior into a single number, 12,13 such as the proportion of days covered (PDC). 7,9 Although this simplification is appealing, it leads to loss of information on medication-taking patterns over time. Group-based trajectory modeling (GBTM) 15 offers an alternative method for summarizing longitudinal data on medication Background-Previous research shows that low socioeconomic position (SEP; especially low income) is associated with statin nonadherence. We investigated the relationship between SEP and statin adherence in a country with universal coverage using group-based trajectory modeling in addition to the proportion of days covered. Methods and Results-Using data from Finnish healthcare registers, we identified 116 846 individuals, aged 45 to 75 years, who initiated statin therapy for primary prevention of cardiovascular disease. We measured adherence as proportion of days covered over an 18-month period since initiation and identified different adherence patterns based on monthly adherence with group-based trajectory modeling. When adjusted for age, marital status, residential area, clinical characteristics, and copayment, low SEP was associated with statin nonadherence (proportion of days covered <80%) among men (eg, lowest versus highest income quintile: odds ratio, 1.41; 95% confidence interval, 1.32-1.50; basic versus higher-degree education: odds ratio, 1.18; 95% confidence interval, 1.13-1.24; unemployment versus employment: odds ratio, 1.17; 95% confidence interval, 1.10-1.25). Among women, the corresponding associations were different (P<0.001 for sex-byincome quintile, sex-by-education level, and sex-by-labor market status interactions) and mainly nonsignificant. Results based on adherence trajectories showed that men in low SEP were likely to belong to trajectories presenting a fast decline in adherence. Conclusions-Low SEP was associated with overall and rapidly increasing statin nonadherence among men. Conversely, in women, associations between SEP and nonadherence were weak and inconsistent. adherence. GBTM accounts for the dynamic nature of adherence and identifies long-term patterns of the repeatedly measured adherence and groups of individuals with similar patterns. 16,17 Statin adherence trajectories have also been shown to predict cardiovascular events.
18Despite the universal healthcare, socioeconomic disparities in CVD have been documented also in Finland: lower SEP has been associated with higher CVD morbidity and mortality, lower use of statins, and lower revascularization rates. 3,[19][20][21] The aim of our study was to determine the association of SEP with nonadherence and adherence trajectories in Finnish patients initiating statin therapy for primary prevention of CVD. To refine the estimation of the effect of SEP on statin nonadherence, we measured adherence as 18-month adherence trajectories in addition to a conventional dichot...