Cognitive Benefits of Reducing Indoor Particulate Matter Exposure During Sleep: New Evidence from a Randomized, Double-blind Crossover Trial

There is increasing evidence that particulate matter (PM) pollution may adversely impact cognition. Considering that sleep is critical for cognitive health and occupies about one-third of human life, understanding the cognitive effects of indoor PM exposure during sleep and the potential cognitive benefits of reducing such exposure is crucial, yet currently unknown. This randomized, double-blind crossover intervention trial was conducted among 80 college students with real and sham PM filtration in their dormitories. Real-time indoor PM levels and nocturnal sleep parameters were monitored, followed by quantification of serum neurotransmitter metabolites and cognitive assessments in the mornings. We found that PM exposure during sleep, particularly PM₁ and PM_2.5, affected immediate and delayed memory, executive function, and global cognition. Reducing PM exposure during sleep resulted in improvements in multiple cognitive domains, with a 0.21 (95% CI: 0.05, 0.36) increase in global cognitive z-score, in which increased sleep oxygen saturation (SpO₂) and alterations in dopamine metabolism and histidine metabolism played important roles. Notably, even when indoor PM_2.5 levels were below the WHO air quality guidelines, further reducing PM exposure could still improve sleep SpO₂ and neurotransmitter metabolism. This study provides a promising strategy to mitigate indoor PM-induced cognitive impairment.