Interrupted time series analysis on first cardiovascular disease hospitalization for adherence to lipid-lowering therapy

Purpose We analysed lipid-lowering medication adherence before and after the first hospitalization for cardiovascular disease (CVD) to explore the influence hospitalization has on patient medication adherence. Methods We extracted a sub-cohort for analysis from 313,207 patients who had primary CVD risk assessment. Adherence was assessed as proportion of days covered (PDC) >= 80% based on community dispensing records. Adherence in the 4 quarters (360 days) before the first CVD hospitalization and 8 quarters (720 days) after hospital discharge was assessed for each individual in the sub-cohort. An interrupted time series design using generalized estimating equations was applied to compare the differences of population-level medication adherence rates before and after the first CVD hospitalization. Results Overall, a significant improvement in medication adherence rate from before to after the hospitalization was observed (odds ratio (OR) 2.49 [1.74-3.57]) among the 946 patients included in the analysis. Patients having diabetes history had a higher OR of adherence before the hospitalization than patients without diabetes (1.50 [1.03-2.22]) but no significant difference after the hospitalization (OR 1.13 [0.89-1.43]). Before the first hospitalization, we observed that quarterly medication adherence rate was steady at around 55% (OR 0.97 [0.93-1.01), whereas the trend in adherence over the post-hospitalization period decreased significantly per quarter (OR 0.97 [0.94-0.99]). Conclusions Patients were more likely to adhere to lipid-lowering therapy after experiencing a first CVD hospitalization. The change in medication adherence rate is consistent with patients having heightened perception of disease severity following the hospitalization.