HIGH-EFFICIENCY particulate arrestance (HEPA) air filtration was associated with improved cognitive performance among adults aged 40 years and older in a secondary analysis of a randomised crossover trial.
The analysis included 119 participants from the Home Air Filtration for Traffic-Related Air Pollution study. Participants were randomly assigned to receive either a HEPA air purifier or a sham unit for 1 month, followed by a 1-month washout period and then the alternative intervention for a further month.
Cognitive performance was assessed at the beginning and end of each intervention period using the Trail Making Test Parts A and B. These tests measured the time required for participants to complete each task.
Overall, the researchers found no significant difference in completion times between periods of HEPA and sham filtration. However, age significantly modified the association between air filtration and cognitive performance (test for interaction: P=0.02).
Among participants aged 40 years and older, those receiving HEPA filtration completed Trail Making Test Part B significantly faster than participants who had received sham filtration during the preceding month.
Mean completion time was 54.0 seconds following HEPA filtration compared with 61.4 seconds following sham filtration. This represented a 12% faster completion time with HEPA filtration (ratio of means: 0.88; P=0.02).
No significant reduction in completion time was observed among participants younger than 40 years.
The findings therefore suggested that the potential cognitive effects of short-term improvements in indoor air quality may differ according to age. The study specifically identified an improvement in cognitive performance among older healthy adults following 1 month of in-home HEPA filtration.
The researchers noted that particulate matter exposure has been associated with adverse health outcomes, including cardiovascular and neurological diseases. However, relatively few intervention studies have examined whether short-term changes in particulate exposure are accompanied by changes in cognitive outcomes.
The current analysis provides evidence of an association between in-home HEPA filtration and improved performance on one measure of cognition among older adults. However, the absence of an overall significant difference between HEPA and sham filtration indicates that the findings should be interpreted in the context of the observed age interaction.
Further research is needed to investigate the short-term cognitive effects of air pollution and air filtration, particularly among individuals with some degree of cognitive impairment.
Pellegrino N et al. Effect of HEPA filtration air purifiers on cognitive function from a secondary outcome analysis of a pragmatic randomized crossover trial. Sci Rep. 2026;16(1):17737.
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