Cognitive decline in relation to later-life high temperature exposure in a Chinese nationwide cohort

Abstract

Growing evidence has linked extreme temperature with neuropsychiatric disorders under climate warming with frequent extreme heat events over the past decades, while cognitive performance in relation to heat exposure remains largely unstudied, particularly in populations at high vulnerability to climate risks (e.g., China). Based on five survey waves of a nationwide dynamic cohort (2011–2020), we analyzed 47,825 cognitive test records from 14,729 respondents aged 45+ years across 126 Chinese cities. Global cognitive performance and its two dimensions (episodic memory and mental status) was measured using standardized questionnaires. Temperature exposure prior to cognitive tests was assessed using both average temperatures and heat days exceeding predefined temperature thresholds. Linear mixed-effects models were utilized to examine the relationship between high temperature exposure and cognitive function. This study revealed consistent evidence for heat-related declines in global cognitive performance and episodic memory across multiple exposure-window analyses, while robust associations were observed solely during prolonged exposure periods (more than 90 d) for mental status. For each 1-°C rise in annual mean temperature within 1 year prior to investigation, cognitive scores declined by 0.058 (95% CI: −0.079, −0.037) points for global performance, 0.033 (95% CI: −0.048, −0.018) points for episodic memory, and 0.025 (95% CI: −0.038, −0.013) points for mental status, respectively. Similar findings were seen in analyses using heat exposure days defined by multiple temperature percentiles, linking per 10-d increase in heat duration to reduced global cognitive scores ranging from −0.142 (95% CI: −0.214, −0.070) to −0.168 (95% CI: −0.254, −0.082). Despite varied evidence by heat exposure metrics and cognitive dimensions, stratified analyses suggested possibly higher susceptibility among females, less-educated, and urban-dwelling residents to heat-related cognitive impairment. These results provided suggestive evidence for the role of exposure to heat in triggering cognitive impairment in middle-aged and older individuals. This finding may be crucial in developing public health strategies for managing climate change risks of neurobehavioral disorders in a healthy aging society.