Health

In-home HEPA air purifiers may improve cognitive function in adults over 40

A study of people living near major highways found a small but notable boost in mental flexibility and executive function after one month of use.

Updated Aug 30, 2026 · 15:20 UTC1 reports

The short version

A study published in Scientific Reports found that adults aged 40 and older completed executive function tests about 12% faster after using a HEPA air purifier for a month compared to a sham filter.
The research was conducted on 119 participants in Somerville, Massachusetts, an area near two major highways with high levels of traffic-related air pollution.
While the findings suggest a potential low-cost method to mitigate cognitive harms from air pollution, researchers noted the study's brief duration and a lack of participants over the age of 60.

The study analyzed data from 119 participants aged 30 to 74 in a randomized crossover trial, where individuals used both a real HEPA filter and a sham filter for one month each.[ScienceDaily]
Participants aged 40 and older, who made up about 42% of the sample, completed a test measuring executive function and mental flexibility 12% faster on average after using the HEPA purifier.[ScienceDaily]
The study took place in Somerville, Massachusetts, which is situated near Interstate 93 and Route 28, making it an ideal location for testing the effects of traffic-related air pollution.[ScienceDaily]

It is not known whether HEPA filters would show a similar or greater benefit for older populations, as fewer than 10 participants in the study were over the age of 60.[ScienceDaily]
The exact biological mechanism of how air purification improves cognition remains unclear, though researchers plan to investigate if reducing particulate matter protects the brain's white matter and alters metabolite levels.[ScienceDaily]
The study only monitored participants for one month, leaving the long-term sustainability of the cognitive benefits undetermined.[ScienceDaily]