Running an air purifier on days with heavy particulate pollution may help the brain as well as the lungs and heart, according to a new study.
Cognitive Speed Improved 12% Among Those Over 40
According to Science Daily and other science media outlets on the 1st, researchers at the University of Connecticut and Tufts University analyzed the relationship between the use of household high-efficiency particulate air (HEPA) filter purifiers and cognitive function.
The most notable change appeared among participants aged 40 and older. After using HEPA filters for one month, they completed a test measuring executive function and cognitive flexibility in an average of 54 seconds. That was 7.4 seconds, or about 12%, faster than the 61.4 seconds recorded when they used sham purifiers without filters.
Actual particulate concentrations also fell sharply in homes where the purifiers were running. In 19 households where indoor air quality was measured separately, fine particulate matter (PM2.5) concentrations dropped 52%, from an average of 5.2 micrograms per cubic meter to 2.5 micrograms. Ultrafine particles (UFP) measuring 0.1 micrometers or less in diameter fell 32%, from 6,925 to 4,706 per cubic centimeter.
The researchers focused on the possibility that reduced exposure to particulate matter was linked to the change in cognitive function. Exposure to particulate matter is known to be associated not only with respiratory and cardiovascular disease but also with neurological disorders such as Alzheimer's disease and Parkinson's disease.
Previous studies in particular raised the possibility that particulate matter affects white matter, the nerve fiber tissue connecting different regions of the brain. Changes in white matter in the frontal and temporal lobes are related to executive function and cognitive flexibility, the areas where improvement appeared in this study.
Testing Purifiers With 119 Residents Near a Highway
The study covered 119 adults living in Somerville, Massachusetts. The area sits close to heavily trafficked roads including Interstate 93, leaving residents relatively more exposed to traffic-related air pollution.
Participants used purifiers fitted with actual HEPA filters for one month, then went through a one-month washout period before using sham purifiers without filters for another month. Other participants ran the experiment in the reverse order. The crossover design had each person experience both conditions to reduce individual differences.
The researchers then administered the Trail Making Test. Connecting numbers in sequence assessed visual search and motor speed, while alternating between numbers and letters measured executive function and cognitive flexibility.
HEPA filters remove fine particulate pollutants from the air at high efficiency. They can capture fine and ultrafine particles to lower indoor particle concentrations, but they do not remove all gaseous pollutants such as nitrogen dioxide or volatile organic compounds.
It Does Not Mean Brains Got 12% Better
The findings should not be read as meaning that turning on an air purifier makes the brain 12% better. The 12% figure does not indicate improved intelligence or overall brain function, but rather the reduction in the time participants aged 40 and older took to complete a specific cognitive test.
An analysis of all 119 participants found no statistically significant difference between the use of HEPA filters and sham filters, and no clear improvement appeared among those under 40 either.
The study also had limitations in its short duration and small sample. There were 50 participants aged 40 and older, and fewer than 10 aged 65 and older. The purifiers were used for only one month, so it remains unconfirmed whether the same effect continues with long-term use or whether it lowers the risk of dementia or cognitive decline.
The researchers said further study is needed on whether the reduction in particulate matter through HEPA filters actually protects white matter in the brain. The findings were published in the international journal Scientific Reports.
