Socioeconomic gradients in tiotropium use among adults with COPD

BACKGROUND: Inequalities in the use of new medications may contribute to health disparities. We analyzed socioeconomic gradients in the use of tiotropium for chronic obstructive pulmonary disease (COPD). METHODS: In a cohort of adults with COPD aged ≥55 years identified through population-based sampling, we elicited questionnaire responses on demographics, socioeconomic status (SES; lower SES defined as high school education or less or annual household income <US $20,000), and medication use and other clinical variables. In a subset we obtained pulmonary function testing. We used multiple logistic regression analysis to estimate the associations between SES and tiotropium use in COPD, adjusting for disease severity measured by a COPD Severity Score. RESULTS: Of 427 subjects, 44 (10.3%) reported using tiotropium in 2006. Adjusting for COPD severity, lower SES was associated with reduced odds of tiotropium use (OR 0.3; 95% CI 0.1–0.7; p = 0.005). Among the subset with lung function data (n = 95), after including COPD Global Obstructive Lung Disease (GOLD) Stage ≥2 in the model, lower SES remained associated with reduced odds of tiotropium use (OR 0.03; 95% CI < 0.001–0.7; p = 0.03). Including forced expiratory volume in one second in the model as a continuous variable instead of GOLD Stage ≥2 yielded similar results for lower SES (OR 0.1; 95% CI < 0.001–0.5; p = 0.02). CONCLUSION: There was a strong SES gradient in tiotropium use such that there was less use with lower SES. To the extent that this is an efficacious medication for COPD, this gradient represents a potential source of health disparities.