Using a home HEPA air purifier for one month led to small but significant improvements in executive function and mental flexibility among adults over 40, according to new research we co-authored published in the journal Scientific Reports.
HEPA stands for High-Efficiency Particulate Air. HEPA air purifiers remove particulate matter from indoor air, including tiny particles linked to respiratory and cardiovascular disease and neurological conditions such as Alzheimer’s and Parkinson’s disease. Environmental health researchers increasingly recommend HEPA filters to reduce exposure to indoor particulate matter, but fewer studies have examined whether using an air purifier can improve cognitive performance.
We analyzed survey data from 119 adults between the ages of 30 and 74 who lived in Somerville, Massachusetts. The city is located near two major highways, Interstate 93 and Route 28, and residents may experience elevated levels of traffic-related air pollution. This made Somerville a useful location for studying the potential health effects of home air purification.
Participants were randomly assigned to one of two groups. One group used a real HEPA air purifier for one month, followed by a sham purifier for another month, with a one-month break between the two periods. The sham purifier looked and operated like the real device but did not contain an air-cleaning filter. The second group used the purifiers in the opposite order.
At the end of each month, participants completed cognitive tests that measured different aspects of mental ability. The tests assessed visual memory and motor speed by measuring how quickly participants could connect consecutive numbers. They also evaluated executive function and mental flexibility by asking participants to connect alternating numbers and letters.
Participants over 40, who represented approximately 42% of the sample, completed the mental flexibility and executive function tasks an average of 12% faster after using the HEPA purifier than after using the sham purifier. The results remained consistent after accounting for differences in purifier use, time spent indoors and participants’ stress levels during testing.
Although a 12% improvement may appear modest, it is comparable to some cognitive benefits associated with increasing daily physical activity. A faster test performance may not feel like a dramatic improvement in mental clarity, but protecting cognitive function is important for long-term health. Even small declines in cognitive ability have been associated with a higher risk of death.
Why is this important?
Air pollution can affect mental performance after only a few hours of exposure. Previous research shows that air purifiers are effective at reducing indoor particulate matter. However, it remains unclear whether lowering indoor pollution can protect cognitive function when people are exposed to ongoing outdoor pollution from sources such as traffic. Research involving people who live near major highways is especially limited.
People who live near highways and heavily trafficked roads are exposed to higher levels of air pollution and may face increased rates of pollution-related disease. These risks are not distributed equally across the United States. People of color and individuals with lower incomes are more likely to live near highways or areas with heavy traffic.
Our findings suggest that HEPA air purifiers may offer meaningful health benefits for people living in these conditions, particularly by reducing exposure to indoor particulate matter.
What is not known yet?
Research indicates that air pollution may begin to have a particularly strong effect on cognitive function around the age of 40, with these effects potentially becoming more pronounced with age.
HEPA air purifiers may therefore be especially beneficial for older adults. However, our study could not fully assess this possibility because fewer than 10 of the 119 participants were 60 or older.
Participants used the HEPA air purifiers for only one month. Longer studies are needed to determine whether the cognitive improvements persist, become stronger or change over time with continued air purification.
It is also unclear exactly how reducing indoor air pollution may improve cognitive function. Some research suggests that exposure to particulate matter can reduce the amount of white matter in the brain. White matter helps brain cells transmit electrical signals and maintain communication between different brain regions. The areas of the brain most affected by air pollution may include those involved in mental flexibility and executive function—the same abilities that improved in our study after participants used a HEPA purifier.
Future research will examine whether using HEPA air purifiers to reduce particulate matter can protect the brain’s white matter or help reverse some forms of cognitive decline. We also plan to study changes in metabolites—molecules produced when cells perform their normal functions—that may occur when people breathe polluted air and when indoor air is cleaned with HEPA filters.
Source: www.sciencedaily.com