HEPA Air Purifiers May Boost Brain Function After Just One Month

A new study finds that using a HEPA (high-efficiency particulate air) air purifier at home for one month produced a small but significant improvement in brain function in adults 40 and older. The findings were published in the journal Scientific Reports.

The researchers analyzed data from 119 people aged 30 to 74 in Somerville, Massachusetts, a city near two major highways with heavy traffic-related air pollution. Participants were randomly assigned to use a real HEPA purifier for one month and a sham purifier, which looked and acted the same but had no air-cleaning filter, for another month, in either order, with a month-long break in between.

After each month, participants took a test of mental flexibility and executive function. Participants 40 and older, about 42% of the group, completed that section 12% faster after the month with the real purifier than after the sham month, even after accounting for time spent indoors and how stressful they found the test. The researchers compared the size of that improvement to the cognitive benefits of increased daily exercise.

Fewer than 10 of the 119 participants were older than 60, so the study did not examine effects in that age group, and it tested only one month of purifier use. The researchers said it remains unclear exactly how air purifiers might improve cognition, though some studies suggest particulate matter reduces the brain's white matter, which helps brain cells conduct signals and maintain connections between regions.