Impact of Patient Reimbursement Timing and Patient Out-of-Pocket Expenses on Medication Adherence in Patients Covered by Private Drug Insurance Plans

BACKGROUND: Adherence to prescribed medications used in the treatment of chronic diseases is suboptimal, and drug insurance plans can have an impact on adherence. There is little evidence on the impact of patient reimbursement timing on medication adherence. OBJECTIVE: To compare adherence to prescribed medications in privately insured patients from Quebec, Canada, with different patient reimbursement timing and levels of patient out-of-pocket expenses. METHODS: A retrospective cohort was constructed by selecting privately insured patients aged 18-64 years from the reMed database (2008-2012) who filled at least 1 prescription for a medication belonging to 1 of the 10 most prescribed drug classes for chronic diseases. Patient reimbursement timing was classified as immediate (immediate patient reimbursement at the point of service of the portion of the medication cost covered by the insurer) or deferred (patient reimbursement at a later time). Patient outof-pocket expenses related to the medication under study at cohort entry (available only for the immediate patient reimbursement group), which included the deductible and the coinsurance, were categorized into 5 levels (null category and quartiles): $0, $0.01-$3.59, $3.60-$8.11, $8.12-$14.40, and $14.41-$89.99. Adherence was measured with the proportion of days covered (PDC) over 1 year among new users of the medication under study. Linear regression models were used to estimate the adjusted mean difference of PDC between groups. RESULTS: There was no difference in medication adherence between the immediate (n = 1,345) and deferred patient reimbursement (n = 437; difference, 0.0%; 95% CI, -3.0 to 3.0). Patients with the highest patient out-of-pocket expenses were less adherent than those with the lowest patient out-of-pocket expenses (difference, -19.0%; 95% CI, -24.0 to -13.0); however, patients with no patient out-of-pocket expenses were less adherent than those with low patient out-of-pocket expenses (difference, -9.0%; 95% CI, -15.0 to -2.0). CONCLUSIONS: Medication adherence appeared to be unaffected by patient reimbursement timing but was affected by the level of patient out-of-pocket expenses. The absence of a correlation between medication adherence and timing of patient reimbursement might be explained by the relatively rapid reimbursement of expenses by insurance companies in Canada. Subjects with no patient out-of-pocket expenses at the point of service might be less adherent because they place less value on their medications than do patients who must pay even a small amount.