Association of Long-term Exposure to Air Pollution and Dementia Risk

Understanding the Link Between Air Pollution and Dementia

Air pollution, which we can all agree is a pervasive environmental issue, has long been associated with various health problems. A 2023 research report published in Neurology has shed light on its impact on cognitive health, particularly the risk of dementia. The study, titled “Association of Long-term Exposure to Air Pollution and Dementia Risk,” explores the biological mechanisms linking air pollution to dementia, emphasizing the roles of homocysteine, methionine, and cardiovascular risk factors.

Key findings

The study used data from a Swedish aging and care study, following 2,512 people without dementia for about 5 years. Researchers looked at levels of two air pollutants: PM2.5 (more on this below) and NOx, from 1990 to 2013. They found that long-term exposure to PM2.5 significantly increased the risk of developing dementia, with a 70% higher risk for every unit increase of PM2.5 in the five years before the study started.

(PM2.5 stands for tiny particles in the air that are 2.5 micrometers or smaller. These particles are so small that they can get deep into your lungs and even enter your bloodstream. Common sources include car exhaust, industrial emissions, and burning wood. Because of their size, PM2.5 particles can cause serious health problems like heart and lung diseases, and recent studies suggest they might also increase the risk of dementia.)

Biological Mechanisms

Homocysteine (tHcy) and methionine played crucial roles in mediating the effects of air pollution on dementia risk. The study found that high levels of tHcy amplified the dementia risk, while high levels of methionine reduced it. Interestingly, about 50% of the total effect of PM2.5 on dementia was mediated through tHcy, either directly or through its interaction with air pollution. Conversely, high methionine levels mitigated the risk by 31%, primarily through direct interaction with PM2.5.


This study provides valuable insights into how long-term exposure to air pollution influences dementia risk through complex biological mechanisms, including the roles of homocysteine and methionine.

Just a note on homocysteine levels – I feel for any neurological condition, it is absolutely imperative to check homocysteine levels. This is possible through a simple blood test. Homocysteine is believed to contribute to cognitive decline through several mechanisms, including neurotoxicity, oxidative stress, and promoting inflammation. These mechanisms can lead to neuronal damage and impaired cognitive function.

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