Alzheimer’s disease is the most common form of dementia. In France, nearly 850,000 people are concerned, according to health insurance. And this figure could still increase in the coming years, especially due to the aging of the population. But beyond age, other risk factors are now identified: tobacco, alcohol, diabetes, overweight, chronic stress, anxiety, depression … and more recently, air pollution.
An increasingly clear link between pollution and cognitive decline
A new study published on July 24, 2025 in the journal The Lancet Planetary Health comes to strengthen this link. Researchers from the University of Cambridge have screened 51 international studies, grouping data of more than 29 million people, to assess the impact of exposure to pollution on the risk of developing dementia.
The result is clear: the greater the exposure, the more the risk increases. On average, each increase of 10 micrograms per cubic meter of fine particles (PM2.5) is associated with an increase of 17 % of the risk of dementia.
Pollution: What are the pollutants in question?
Researchers have identified three main types of particularly worrying pollutants:
- Fine particles (PM2.5): from exhaust gases, power plants, industries or even wood heating, they are so small that they can penetrate deep into the lungs … or even reach the brain;
- Nitrogen dioxide (NO₂): Present in exhaust gases and industrial smoke, it aggravates respiratory disorders and could play a role in neurodegenerative diseases;
- SUID (black carbon): also from combustion, it contributes to air pollution and can infiltrate our body, affecting heart, lungs … and brain.
How does pollution act on our brain?
Scientists advance a disturbing explanation: pollution would disrupt blood circulation in the brain, especially in areas responsible for memory. This poor irrigation would reduce oxygen intake and promote the appearance of brain damage, one of the mechanisms suspected in the development of Alzheimer’s.
Another hypothesis mentioned: chronic inflammation and oxidative stress, caused by pollutants, could also contribute to neuronal degeneration.
Towards a new approach to prevention?
This discovery resumes cards on the way we see prevention. Until then, research on Alzheimer had mainly focused on internal causes of the brain, such as the accumulation of abnormal proteins. But this study shows that the external environment also plays a major role.
And unlike age or genetics, pollution is a modifiable factor. In other words, by collectively acting on air quality, we could also protect our long -term mental health.
“These results show that fighting pollution is not limited to respiratory or cardiovascular disease. This can also reduce the risk of dementia”insists Dr. Haneen Khreis, the main author of the study.
How to protect yourself on a daily basis?
Difficult to protect yourself against this aspect. The solution is not only individual. Researchers call for ambitious public policies: stricter regulation of industrial emissions, less polluting transport, more sustainable town planning …
But everyone can also act at their level:
- Consult the air quality index before going out, especially if you are sensitive (elderly, chronic patients, etc.). The IQAir site gives real -time data in many cities, underlines the Top Health site;
- Wear a mask during pollution peaks;
- Avoid highly frequented roads for your trips on foot or by bicycle;
- Adopt a healthy lifestyle: balanced diet, physical activity, good sleep, stopping smoking and alcohol, monitoring of tension and blood sugar. These gestures remain essential for Alzheimer’s prevention.
While cases of dementia explode, this discovery recalls the urgency of a collective fight for a healthier air. Because to breathe is vital, for the body as for the mind.