Interaction effects of extreme temperature events and air pollutants on neurodegenerative disease mortality: A case-crossover study in a cold-winter, hot-summer region of China

Extreme temperature events (ETEs) and air pollutants are both linked to neurodegenerative diseases, yet their interactions remain underexplored. This case-crossover study examined the effects of ETEs and six ambient air pollutants (PM 10 , PM 2.5 , O 3 , SO 2 , NO 2 , and CO) on mortality due to neurodegenerative diseases in a cold-winter, hot-summer region of China (2014–2021). Using a conditional logistic regression model combined with a distributed lag non-linear model, we found that heat wave and cold spell significantly increased overall neurodegenerative disease mortality, with peak effects at lag 0–14 days for heat wave (OR=1.77[95 %CI: 1.58, 1.98]) and lag 0–8 days for cold spell (OR=1.25[95 %CI: 1.10, 1.42]). All six air pollutants were significantly associated with mortality during the warm season, with PM 2.5 and SO 2 posing higher risks. Positive interactions were observed between heat wave and four air pollutants (PM 10 , PM 2.5 , SO 2 , CO), particularly with SO 2 (interaction OR = 1.84[95 %CI: 1.68, 2.01]). The strongest interaction effects were found for Alzheimer’s disease mortality across all subcategories. Vulnerable groups included females, individuals aged > 80 years, and those without a spouse. These findings highlight the compounded risks of ETEs and air pollution on neurodegenerative disease mortality, emphasizing the need for synergistic warning systems and targeted control measures. This study provides evidence for the interaction between short-term exposure to extreme temperature events and air pollutants on neurodegenerative disease mortality. • Heat wave combined with air pollutants increase neurodegenerative mortality. • Alzheimer’s deaths are most affected by ETEs–pollutant interactions. • Females, adults aged > 80 and those without spouses face higher risk.