Effect of cost-sharing on use of asthma medication in children.

OBJECTIVE To examine the effect of cost-sharing on the use of asthma medications in asthmatic children. According to asthma guidelines, children with asthma may require treatment with multiple medications, including controllers and relievers, to achieve optimal control. Although families may be enrolled in drug benefit plans, impediments to access persist in the form of cost-sharing. DESIGN Population-based retrospective cohort study of children by analysis of administrative medication insurance claims data. SETTING Ontario, Canada. PARTICIPANTS A cohort of 17 046 Ontario children with asthma enrolled in private drug plans. Main Exposure We used data on out-of-pocket expenses and reimbursement for medications to classify children as having zero, low (< 20%), or high (> or = 20%) levels of cost-sharing. MAIN OUTCOME MEASURES We examined use of bronchodilators, inhaled corticosteroids, leukotriene receptor antagonists, oral corticosteroids, and combination agents. Multiple linear and logistic regressions compared medication use between cost-sharing groups, controlling for age and sex. RESULTS The annual number of asthma medication claims per child was significantly lower in the high cost-sharing group (6.6) compared with the zero (7.0) and low (7.2) cost-sharing groups (P < .001). Children in the high cost-sharing group were less likely to purchase bronchodilators, inhaled corticosteroids, and leukotriene receptor antagonists compared with the low cost-sharing group (odds ratio, 0.76; 95% confidence interval, 0.67-0.86) and were less likely to purchase dual agents compared with the low cost-sharing group (odds ratio, 0.70; 95% confidence interval, 0.66-0.75). CONCLUSION The cost-sharing level affected the use of asthma medication, with the highest cost-sharing group exhibiting significantly lower use of maintenance medications and newer dual agents.