Air pollutants have been confirmed to increase the risk of Alzheimer's dementia.
A joint research team said Thursday that air pollutants, including fine dust, reduce the thickness of the cerebral cortex, increasing the risk of Alzheimer's.
Professors Cho Jae-rim and Kim Chang-soo of Yonsei University College of Medicine’s Prevention Medicine Class and Professor Roh Young of the Neurology Department at Gachon University Gil Medical Center conducted the study.
Air pollutants enter the lungs through the respiratory tract and cause inflammation, which causes various diseases throughout the body, especially the inflammation of nerves when it reaches the brain. The research team confirmed through previous studies that air pollutants affect the atrophy of the cerebral cortex. Still, no evidence exists that this phenomenon led to cognitive decline and Alzheimer's.
Cortical changes in the cerebral cortex are closely related to brain diseases, including Alzheimer's. The average cerebral cortex thickness in healthy ordinary people is 2.5 millimeters, but that of patients with Alzheimer's was thinner, with 2.2mm.
The researchers studied the effects air pollution has on brain health using three primary air-polluting materials – ultrafine dust (PM2.5), fine dust (PM10), and nitrous oxide (NO2) – as indicators in 640 healthy adults 50 and older with no brain diseases in Seoul, Incheon, Wonju and Pyeongchang for 32 months from August 2014.
The result showed that the thickness of the cerebral cortex decreased as the concentration of air pollutants increased. For instance, when the concentration of fine dust and ultrafine dust increases by 10μg/, and nitrogen dioxide increases by 10ppb, the thickness of the cerebral cortex decreases by 0.04mm, 0.03mm, and 0.05mm.
Afterward, to compare the subjects’ cerebral cortex thickness to Alzheimer's patients, the team conducted an "Alzheimer's brain atrophy index assessment,” which predicts the risk of Alzheimer's with brain image-based artificial intelligence techniques.
As a result, they found the decreased cerebral cortex due to air pollutants was similar to the atrophied area of the cerebral cortex in Alzheimer's patients.
If brain areas that control thinking, attention, spatial perception, and memory, such as the frontal lobe, temporal lobe, parietal lobe, and cephalic lobe, reduce, their lowered function triggers dementia. Researchers discovered that the subjects, like Alzheimer's patients, saw all four parts of the cerebral cortex contract during the experiment.
When the concentration of fine dust increases by 10μg/㎥, the frontal lobe and temporal lobe thickness fall by 0.02mm and 0.06mm. The comparable increase in ultrafine dust led to a fall in the thickness of the temporal lobe by 0.18mm. When the concentration of nitrogen dioxide increased by 10 ppb, the thickness of the frontal and parietal lobes fell by 0.02mm, the temporal lobes by 0.04mm, and the cerebral fibula by 0.04mm.
The researchers confirmed that if the concentration of air pollutants rises, the cognitive function also decreases.
A 10㎍/㎥ increase in ultrafine dust, fine dust, and nitrous oxide led to the cognitive function scores dropping by 0.69, 1.13, and 1.09 points. This means the subjects' calculation, language, and memory abilities decreased because of air pollutants.
Besides, a 10㎍/㎥ increase in ultrafine dust, fine dust, and nitrous oxide increased the risks of mild cognitive impairment, a pre-stage leading to Alzheimer's, by 1.5, 2.2, and 1.7b times.
“This study has shown that air pollutants shrink the cerebral cortex, thereby reducing cognitive function and increasing the dementia risk,” Professor Cho said. “It is better to refrain from going out and wear a health mask when you conduct outdoor activities when air pollution is severe.”
The study, conducted with the support of the National Research Foundation of Korea, was published in the latest issue of Environment International.