A total of 27,585 participants were recruited from March 2005 to November 2014. Participants were excluded if they were younger than 65 years at baseline (n=556), had cognitive impairment [Mini-mental Status Examination (MMSE) score < 18] at baseline (n=7,625), had a diagnosis of stroke or cerebrovascular disease at baseline (n=991), with no follow-up assessments (n=8,102), or had unavailable ozone exposure information (n=767). The total sample thus consisted of 9,544 individuals. Abbreviation: CLHLS, Chinese Longitudinal Healthy Longevity Survey.