Purpose
To assess longer-term patterns of glaucoma medication adherence and identify whether patterns of adherence established during the first year of medication use persist during three additional years of follow-up.
Methods
We conducted a retrospective longitudinal cohort analysis of beneficiaries enrolled in a U.S. managed care plan for ≥7 years between 2001-2012 who were ≥40 years old and newly diagnosed and treated for open-angle glaucoma. Group-based trajectory modeling (GBTM) classified patterns of adherence using the medication possession ratio (MPR) during the first year and over four years of follow-up. We compared beneficiaries to identify whether patterns of medication use in year 1 persisted over the 4 years. We identified socio-demographic and other factors associated with ideal patterns of adherence with regression analyses.
Results
Of the 1,234 subjects included, GBTM identified five distinct patterns of glaucoma medication adherence in both the one-year and four-year follow-up periods. The five groups were: 1) Never adherent after their index prescription fill (7.2%,15.5% of subjects in the one and four-year models, respectively); 2) Persistently very poor adherence (17.1%, 23.3%); 3) Declining adherence (9.1%, 9.1%); 4) Persistently moderate adherence (45.6%, 36.7%); and 5) Persistently good adherence (21.0%, 15.4%). At least 90% of beneficiaries in the 4 groups with the worst and best adherence patterns (Groups 1, 2, 3, 5) maintained their patterns from their first year throughout their 4 years of follow-up while those with mid-level adherence (Group 4) were most likely to change groups. Regression analyses identified that those with the best adherence over 4 years were more likely to be white, older, earn >$60,000/year, use mail order either exclusively or along with their local pharmacy and have more eye care visits (p<0.05 for all comparisons).
Conclusions
For most patients newly-started on glaucoma medications, adherence patterns observed in the first year of treatment reflect patterns of adherence over the subsequent 3 years. Investing resources in both identifying and helping patients with suboptimal adherence patterns over the first year may have a larger impact on longer-term adherence.