Shocking discovery: Air pollution increases the risk of dementia

Breathing polluted air can not only damage your lungs but also silently and seriously affect your brain.

In one of the largest studies ever conducted and recently published, scientists analyzed health data from nearly 30 million people and found that long-term exposure to common air pollutants—like vehicle exhaust and industrial fumes—was linked to a higher risk of dementia. These tiny particles can penetrate deep into the body and cause memory and cognitive decline over time.

Global problem

Statistics show that more than 57 million people worldwide are currently living with dementia, including Alzheimer's. This number is expected to nearly triple to 152.8 million by 2050 – placing a heavy burden on families, healthcare workers and global health systems.

Although rates of the disease are showing signs of decline in Europe and North America, the situation is worrying in many other places – especially low-income areas.

Air pollution: the emerging 'culprit'

In recent years, several studies have suggested a link between air pollution and the risk of dementia. However, the evidence is still scattered and weak.

To shed more light on this issue, scientists at the Medical Research Council (MRC) Epidemiology Unit at the University of Cambridge conducted a large-scale meta-analysis, published in the journal The Lancet Planetary Health .

They pooled 51 studies with data on more than 29 million people – mostly from developed countries. Of these, 34 were eligible for in-depth analysis, including 15 from North America, 10 from Europe, 7 from Asia and 2 from Australia.

Research shows a clear link between dementia risk and three types of pollutants:

1. PM2.5 (fine dust ≤2.5 micron in diameter): comes from vehicle exhaust, wood burning, industry, power plants. These dust particles are small enough to penetrate deep into the lungs and remain in the air for a long time.
   
   
2. NO₂ (Nitrogen Dioxide): comes from burning fossil fuels, especially diesel engines and gas stoves. NO₂ can cause inflammation of the airways and reduce lung function.
   
   
3. Soot: Formed from vehicle exhaust or fuel combustion. Soot can heat the atmosphere and, when inhaled, can affect the heart and respiratory system.

How much does the risk increase?

1. Every 10 μg/m³ PM2.5 → risk of dementia increases by 17%
   
   
2. Every 10 μg/m³ NO₂ → 3% increased risk
   
   
3. Every 1 μg/m³ of soot → 13% increased risk
   
   

By comparison, the average PM2.5 concentration in central London in 2023 is around 10 μg/m³ – just above the threshold that raises risk by 17%.

Scientists believe that pollution damages the brain through two main mechanisms: brain inflammation and oxidative stress – a type of reaction that damages cells and DNA. Both have been shown to play an important role in the onset and progression of dementia.

Additionally, dust particles can cross the blood-brain barrier, enter the circulatory system, and cause widespread inflammation throughout the body.

Not just a medical matter

Although most of the research data comes from rich countries and white people, disadvantaged groups – who are more exposed to air pollution – could benefit most from improved air quality.

'Preventing dementia is not just a medical responsibility,' said study co-author Dr Christiaan Bredell. 'Smart cities, transport policy and environmental planning all need to be involved in this fight.'

David Pac

Update 17 August 2025