Fig. 1. Flowchart showing the sample selection. This is a stratified random sampled cohort study with approximately a million subjects. First, the sample was divided into the AD group (n = 213,999) who met the AD criteria defined in this study between 2002 and 2015, and the control group (n = 894,370). Then, in the AD group, if a patient had a previous AD history between 2002 and 2005 (n = 83,564), was < 20 or ≥ 100 years old (n = 76,654), diagnosed with CVD prior to the index date or within 90 days after the index date (n = 466), or had incomplete information on covariates (n = 12,803), then the patient was excluded from the study population. After that, selected patients with AD were matched 1:1 with controls who had never been diagnosed with AD from 2002 to 2015 based on the covariates at the index date of patients with AD using PSM.

AD, atopic dermatitis; CVD, cardiovascular disease; PSM, propensity score matching; NHIS, National Health Insurance Service.