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Air pollution may contribute to the development of dementia
Last reviewed: 02.07.2025
A study published in BMC Public Health found that chronic exposure to pollutants, particularly fine particulate matter (PM2.5) and nitrogen dioxide (NO2), is associated with negative cognitive outcomes and an increased risk of dementia.
Dementia is a severe neurodegenerative disease that affects millions of people worldwide. The number of people with dementia is expected to more than double by 2050, putting significant strain on healthcare systems. In addition to genetic factors, lifestyle and environmental exposures, particularly air pollution, play an important role in the development of dementia.
Previous studies have shown that even small increases in pollutants such as PM2.5 can significantly increase the risk of dementia. Eliminating exposures such as air pollution may help reduce the risk of cognitive decline, especially among older adults.
The researchers conducted a systematic review to examine the association between different types of pollutants and the risk of dementia. Pollutants included PM10, PM2.5, NO2, ozone (O3), black carbon (BC), polycyclic aromatic hydrocarbons (PAH), benzene, toluene, ethylbenzene, xylenes (BTEX), and formaldehyde (FA). Articles that did not meet the criteria, such as reviews, studies not focusing on dementia, and articles with a high risk of bias, were excluded.
A total of 14,924 articles were reviewed, of which 53 studies conducted in 17 countries were included in the analysis. The majority of studies were conducted in the United States and included 173,698,774 participants.
The analysis showed that chronic exposure to pollutants such as PM2.5 and NO2 increases the risk of hospitalization for Alzheimer's disease and worsens neurocognitive disorders. Exposure to air pollution affects episodic memory, hippocampal structure, and brain atrophy. Pollutants can disrupt the blood-brain barrier, cause oxidative stress, and contribute to pathological processes such as amyloid and tau protein accumulation, leading to cognitive decline.
Exposure to pollutants has also been shown to increase the risk of vascular dementia (VaD) through mechanisms including vascular injury and disruption of the blood-brain barrier. This leads to dysfunction of the neurovascular unit, cerebral cortical infarctions and chronic cerebral hypoperfusion, ultimately leading to cognitive impairment.
Despite some conflicting evidence, most studies support a link between air pollution and vascular dementia, highlighting the need for further research into environmental factors in the development of dementia.
The study also found that increased PM2.5 exposure was associated with an increased risk of hospitalization for Parkinson’s disease (PD). More than 80% of patients with PD develop dementia, and its prevalence increases to 50% after 10 years. Only two studies looked at frontotemporal dementia (FTD), with one finding no association between air pollution and FTD and the other finding that chronic PM2.5 exposure reduced gray matter volume in areas associated with FTD.
The study found a significant association between chronic exposure to pollutants and the development of Alzheimer's disease and vascular dementia. The results highlight the need for further research into the mechanisms by which air pollution contributes to cognitive decline.
Addressing modifiable risk factors such as air quality can help prevent or delay the onset of neurodegenerative diseases, reducing their impact on population health and health systems.