Air pollution was believed to be confined to respiratory diseases and alerts against a heat wave. But it also gnaws, silently, what we have most precious: our brain.
on Jul 29 2025, at 8 h 25 min
Atmospheric pollution, this invisible threat, already digs our memory before gnawing on our arteries. As it stands, the projections are overwhelming: 153 million cases of dementia by 2050.
Air pollution, a slow poison for the brain
In a study published on July 24, 2025 in The Lancet Planetary Health, a team of researchers from the University of Cambridge draws a detour conclusion: prolonged exposure to air pollution significantly increases the risk of developing dementia. Yes, polluted air may be crazy. Not symbolically. Literally. Not a hypothesis, not a vague correlation. The authors rely on a meta-analysis of 51 studies, relating to more than 29 million people. Figures that force respect. And concern.
The results are relentless. For each increase of 10 micrograms per cubic meter of fine particles (PM2.5) in the air, the risk of dementia climbs by 17 %. The soot makes this risk of 13 % jump for each microgram. Nitrogen dioxide, typical exhaust jars, adds another 3 % to the meter. Behind these figures, a reality that Dr. Haneen Khreis, main author of the study coldly sums up: “Our work provides additional evidence that prolonged exposure to external pollution is a risk factor in dementia in healthy adults ».
Brain inflammation, oxidative stress: the toxic duo
It is no coincidence that pollution is also harmful to our brain. The mechanisms are now better understood. Once inhaled, the ultrafine particles enter the lungs, cross the blood barrier, reach the solid organs, then … the brain. They trigger a cascade of inflammation and oxidative stress. Result: damaged neurons, amyloid plates that accumulate, and the door open to dementia, Alzheimer’s in mind. Professor Christiaan BREDELL, co-author of this study, drives the point home: “Preventing dementia is not only a medical matter. Town planning, environmental regulations, the choices of transport are just as concerned ».
Beware of shortcuts nevertheless. Air pollution is not the only culprit. Aging, genetic factors, cardio-metabolic diseases, social isolation or even food play a much heavier role. But this environmental factor, modifiable and widely ignored so far, could well be the key to a more ambitious prevention policy. The Door Isode Radford, Alzheimer’s Research Uk, affirms it without detour: “If no one was exposed to pollution, three cases of dementia in a hundred could be avoided». Does that seem little? Reported to the 57 million current cases, a million and a half of lives would change trajectory.
From London to Beijing: who breathes the most dementia?
The authors of the study highlight this with a touch of bitterness. Their data mostly comes from rich countries. However, it is the most marginalized – urban, poor populations, overrepresented in the most polluted areas – who pay the heaviest tribute. In some Asian or African mega -cities, PM2.5 levels happily exceed 50 µg/m³. Or five times more than the exposure thresholds studied. And yet these populations are still underrepresented in research. It’s not just a methodological bias. It is an upcoming health scandal.
The link is now scientifically established. But the political reaction remains timid. Haneen Khreis calls for a “systemic change”, a burst comparable to the fight against smoking or cardiovascular disease. Clean transport, decarbonized energy, stricter standards: the arsenal is known. What is missing? Will.
Read also: How to stimulate your brain to prevent Alzheimer’s?
