One month of in-home HEPA purifier use improves brain function in adults 40 and older

Using a HEPA air purifier at home for a month leads to a small but statistically meaningful improvement in brain function among adults aged 40 and over.

That finding comes from a new study we co-authored, published in Scientific Reports.

How HEPA air purifiers cut particulate matter

HEPA purifiers (HEPA stands for high-efficiency particulate air) are designed to filter particulate matter out of indoor air.

Breathing in particulate matter has been linked with respiratory and cardiovascular conditions, and also with neurological diseases including Alzheimer’s and Parkinson’s.

Environmental health researchers are increasingly advising people to use HEPA air purifiers at home to reduce exposure to particulate matter. However, there has been limited research into whether using them translates into better mental performance.

Study design and cognitive testing in Somerville, Massachusetts

We examined results from a study involving 119 people aged 30 to 74 who lived in Somerville, Massachusetts.

Somerville lies alongside Interstate 93 and Route 28, two major roads that contribute to comparatively high levels of traffic-related air pollution. That makes it a particularly suitable place to test potential health effects of air purifiers.

Participants were randomly allocated to one of two groups. One group used a HEPA air purifier for one month and then, after a month-long break, used a sham air purifier for one month. The sham unit looked and operated like the real one, but it did not include the air-cleaning filter. The other group followed the same schedule but in the opposite order, using the sham purifier first and the real purifier second.

At the end of each month, participants completed a test assessing several aspects of cognitive ability.

The test assessed visual memory and motor speed by timing how quickly people could draw lines linking numbers in sequence. It also evaluated executive function and mental flexibility by asking participants to draw lines between alternating sequential numbers and letters.

We found that participants aged 40 and over-around 42% of the sample-completed the portion measuring mental flexibility and executive function 12% faster on average after using the HEPA purifier than after using the sham purifier.

This pattern remained even after we adjusted for factors such as differences in how long participants spent indoors while using each device, and how stressful they perceived the test to be.

Although the change may appear modest, it is comparable to the cognitive gains people can see from increasing how much they exercise each day.

A 12% improvement is unlikely to feel like an instant surge in mental clarity, but slowing or preventing cognitive decline matters for long-term health. Even relatively small drops in cognitive functioning may be linked with a higher risk of death.

Why it matters

Air pollution can impair mental performance after only a few hours of exposure. Research shows air purifiers can reduce particulate levels, but it is still uncertain whether those reductions can protect against cognitive harm when pollution sources-such as traffic-are persistent.

There has been a particular shortage of research involving people who live close to major air pollution sources, including motorways.

Those living near motorways or other major roads tend to experience higher air pollution exposure and higher rates of diseases associated with air pollution. These risks are not shared evenly across the US: people of colour and people on lower incomes are more likely to live near motorways or in areas with heavy traffic.

Our findings indicate that HEPA air purifiers could provide meaningful health benefits in these kinds of settings.

What still isn't known

Evidence suggests air pollution starts to have a particularly strong effect on cognitive function from around age 40, and these impacts may become more noticeable as people get older.

For that reason, HEPA air purifiers might be especially helpful for older adults. Our study could not properly test that idea, because fewer than 10 of the 119 participants were aged over 60.

In addition, participants used a HEPA air purifier for only one month. It is possible that longer periods of air cleaning could maintain-or even enhance-the improvements in cognitive function we observed.

Finally, the precise mechanism by which air purifiers might improve cognition remains uncertain. Some studies indicate that particulate matter exposure reduces the brain’s white matter, which helps brain cells transmit electrical signals and supports connections between different brain regions.

The parts of the brain that appear to be most affected by air pollution are those involved in mental flexibility and executive function-the same areas in which we observed improvements.

We intend to investigate whether lowering particulate matter with air purifiers is protecting the brain’s white matter, and whether it might reverse some aspects of cognitive decline.

To do this, we will examine how levels of molecules known as metabolites-substances cells produce as they carry out their functions-shift in response to breathing polluted air compared with air cleaned using a HEPA filter.

The Research Brief is a short take on interesting academic work.

Nicholas Pellegrino, Research Associate in Public Health Sciences, University of Connecticut; Doug Brugge, Professor of Public Health Science and Community Medicine, University of Connecticut, and Misha Eliasziw, Associate Professor of Biostatistics, Public Health and Community Medicine, Tufts University

This article is republished from The Conversation under a Creative Commons licence. Read the original article.