Cognitive benefits of air purification among schoolchildren: A randomized, double-blind, crossover trial

Particulate matter was shown to significantly affect children's cognition through intermediate-term to long-term exposure; however, whether and to what extent air purification can improve the neurodevelopment of schoolchildren remains unclear. We conducted a randomized, controlled, double-blind, crossover trial for cognitive health among primary children aged 10-12 years through a multi-setting, mid-term air-purification intervention in Henan Province, China. The intervention and control groups received alternative true or sham purification in classrooms and bedrooms in a random manner. The two intervention phases (76 days) were separated by a washout period of 88 days. Among 57 participants, air purification reduced personal exposure to PM_2.5 from 35.13 to 18.19 μg/m³. For academic performance, compared to the control group, the intervention group showed significant increases (0.22, 0.20, 5.19, and 4.11, respectively) in the improvement of standardized Chinese score (derived from raw scores through Z score transformation), total score (including Chinese and math), Chinese ranking, and total ranking. Regarding the cognitive-function test, executive function was significantly improved in the intervention group. For example, there were greater reductions in total errors (10.58) and non-perseverative errors (10.31) and more pronounced improvements in completed categories (12.94) and conceptualized thinking (2.02). We also observed significant increases in plasma amyloid β42 associated with the intervention. The improvements in cognitive health were also associated with reduced personal PM_2.5 concentrations. Collectively, this trial provides robust evidence that mid-term, multi-setting indoor air purification can significantly enhance cognitive health in children in areas with high air-pollution levels.