figs1.

Study sample selection flowchart. NHANES: National Health and Nutrition Examination Survey. Participants' data from NHANES2003-2004 were retrieved. Participants were included for this study when data on ABI measurement, serum vitamin C, and smoking status according to the questionnaire and serum cotinine level were available. We also excluded the participants’ data when ABI is more than 1.5. In total, there are 2383 participants in our final analysis. Among them, 912 participants were coded a current smoker, and 1471 participants were coded a non-current smoker 1