Figure 2 Overall distribution of patients with carbon monoxide (CO) poisoning according to (A) sex and (B) standardized incidence ratios (SIR) (100 000 person/year) of newly diagnosed stroke by age groups. The incidence of CO poisoning was higher in males than in females, and the numbers of patients with CO poisoning peaked in those aged 30–39 years. Although SIRs tended to increase with age, the observed number of patients who developed stroke after CO poisoning was higher in those aged ≤54 years than those aged ≥75 years.