Fig. 1

Distribution of the total number of ED visits (a) and of income categories (b) with COPD as the primary diagnosis by region of residence.* Multivariable model adjusted for gender, race, Charlson score, beta-blockers, diuretics, ACE inhibitors and statins. X-axis represents the respective age, gender and race category and the y-axis hazard ratio. Each column represents the hazard ratio for that patient characteristic. Reference category is no allopurinol use (use = 0 days), marked by hashed line passing through the hazard ratio of 1.00. Error bars represent 95 % confidence interval