HEPA air purifiers may give older adults a small but measurable boost in brain function after just one month of use. A new study published in the journal Scientific Reports shows that adults aged 40 and older who used a high‑efficiency particulate air (HEPA) purifier in their homes performed better on cognitive tests than when they used a sham device that looked the same but did not clean the air. The study followed 119 participants in Somerville, Massachusetts, a city that sits near two busy highways and therefore experiences high levels of traffic‑related air pollution. The researchers wanted to see whether reducing indoor particulate matter could protect the brain from the harmful effects of outdoor pollution.
HEPA purifiers are designed to trap tiny particles that can travel through the air. They use a dense filter that captures dust, pollen, smoke, and even some bacteria and viruses. Because many of these particles are linked to respiratory and heart problems, scientists have started to look at their impact on the brain. Long‑term exposure to fine particulate matter has been associated with conditions such as Alzheimer’s disease and Parkinson’s disease. By removing these particles from indoor air, HEPA purifiers may reduce the amount of harmful material that reaches the lungs and, eventually, the brain.
The research team recruited 119 adults between the ages of 30 and 74. They lived in Somerville, a city that is close to Interstate 93 and Route 28, two major highways that produce high levels of traffic pollution. This setting made the study ideal for testing whether an indoor air purifier could offset the outdoor pollution that residents normally inhale. Participants were randomly assigned to one of two groups. One group used a real HEPA purifier for one month, then switched to a sham purifier for the next month, with a one‑month break in between. The other group used the devices in the opposite order.
After each month, participants completed a battery of cognitive tests. The tests measured several aspects of mental ability. One part of the test looked at visual memory and motor speed by asking participants to draw lines between numbers that appeared in order. Another part examined executive function and mental flexibility by having them draw lines between alternating numbers and letters. The tests were designed to be quick, but they required careful attention and coordination.