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Breathing clean air is good for the lungs and the heart, but could it also help the brain? According to a new US study published in Nature Scientific Reports, using an air purifier equipped with a HEPA particulate filter in the home could improve some cognitive abilities in adults over the age of 40. This discovery opens new avenues of exploration in the relationship between air quality and brain health.
The study: 119 adults exposed to air pollution
The study, published in April, involved 119 adults between the ages of 30 and 74 living in areas characterised by high vehicular traffic and thus with greater air pollution exposure. The participants used air purifiers with HEPA filters (High-Efficiency Particulate Air filter) for one month, then stopped for a month, then spent a month using placebo devices, identical in appearance but without any actual filtering capacity.
To assess any cognitive changes, researchers had the participants take the Trail Making Test a neuropsychological test used to evaluate attention, processing speed, executive functioning, and mental flexibility. The results showed that adults 40 years and older completed one of the tests about 12 percent faster after having used the HEPA purifier compared with after the placebo period. In the younger age group, however, no statistically significant differences were noted.
Why is pollution able to affect our brains?
In recent years, numerous studies have pointed out that air pollution and exposure to particulate matter (meaning airborne solid and liquid particulates which may be even smaller than 0.1 micrometres in size) do not only cause problems for the respiratory and cardiovascular systems. As a matter of fact, they have also been linked to neurological diseases such as Alzheimer’s and Parkinson’s. Some research has suggested that this is caused by alterations in the brain's white matter – whose essential role involves helping nerve cells to transmit electrical signals and maintain the connections between the different regions of the brain – as well as by neuroinflammation and oxidative stress. It is no coincidence that the regions of the brain most harmed by pollution are those that control mental flexibility and executive functioning, the same areas in which the researchers witnessed improvements.
The benefits of HEPA filters
According to the authors of the study, lowering our daily exposure to particulates could therefore have beneficial effects on our mental performance. HEPA filters could be one way to help with this, since in theory they could remove at least 99.97 percent of dust, pollen, mould, bacteria, and other airborne particulates 0.3 micrometres in size, thus including many of the most harmful types of indoor pollutants. In fact, contrary to what we might think, the air indoors may contain even higher concentrations of harmful pollutants than are found outside the home: fine particulate matter, allergens, smoke, cleaning products, substances released by furniture and construction materials all affect the quality of the air that we breathe every day.
However, it should be noted that the authors of the study themselves advise caution: the improvement they witnessed was, in fact, small, and does not necessarily translate into an immediately noticeable boost in mental acuity. Moreover, a purifier on its own is certainly not enough to prevent neurodegenerative diseases. The researchers went on to underscore that it is not yet clear whether comparable benefits would be observed in people with cognitive impairments or in other population groups. Further studies are thus needed in order to confirm these results and shed light on the biological mechanisms involved.
Air quality and quality of life
This notwithstanding, it has been shown that even minor decreases in cognitive function can be linked to increased mortality risk. If future research confirms the outcomes of this US study, improving the quality of the air in our homes could become a strategy for giving us a better quality of life, and perhaps even a longer one.
