Long-term Ozone Exposure and Cognitive Impairment among Chinese Older Adults: Analysis of the Chinese Longitudinal Healthy Longevity Survey

Abstract

BACKGROUND AND AIM: Increasing evidence points to an association between PM₂.₅ exposure and late-life cognitive health, but little is known about whether ambient ozone exposure affects cognitive functioning. This study aimed to examine the association of long-term ozone exposure with risk of cognitive impairment among older adults in China. METHODS: We used longitudinal data from five waves (2005, 2008-2009, 2011-2012, 2014, and 2017-2018) of the Chinese Longitudinal Healthy Longevity Survey. In total, 9,544 participants (aged 81.4 ± 10.8 years at baseline, 48.3% male) with normal cognitive function at the baseline surveys from March 2005 to November 2014 were included in this analysis. The ozone exposure of each participant was estimated by the cumulative annual average ozone concentration for the county of residence. Cognitive function was assessed by the Chinese version of the Mini-Mental State Examination (MMSE). We used a cutoff MMSE score below 18 points with an additional restriction of MMSE decline ≥ 4 points from baseline to define cognitive impairment. A Cox proportional hazard model was utilized to explore the association of ozone exposure with cognitive decline. RESULTS:During an average observation time of 6.5 years (62,133 person-years), 2,601 participants developed cognitive impairment. Preliminary results show that each 10-μg/m³ increase in ozone was associated with a 13.1% increased risk of cognitive impairment [95% confidence interval (CI): 6.8%, 19.8%]. No evidence was found for a threshold down to 70 μg/m³. The association between ozone exposure and risk of cognitive impairment was stronger for men than women (p-value for interaction: 0.03). CONCLUSIONS:Long-term exposure to ozone was associated with an increased risk of cognitive impairment among Chinese older adults. Reducing ambient ozone pollution may delay cognitive decline among older adults in China. KEYWORDS: Ozone, Long-term exposure, Neurodegenerative outcomes