Air pollution linked to higher risk of dementia

Desiree Burns
September 21, 2018

The increased incidence of dementia in areas with high levels of air pollution could not be explained by other factors known to increase risk of the disease.

"The diseases that cause dementia can begin in the brain up to 20 years before symptoms start to show". The researchers ranked each adult's postcode into fifths, based on which areas had the highest and lowest air and noise pollution.

In general, more research is needed to determine what could be driving the link between environmental factors such as air pollution and dementia risk and whether there could be a causal relationship, said Dr. Thomas Wisniewski, director of the Center for Cognitive Neurology at NYU Langone Health in NY, who was not involved in the new study. He said that this study would encourage further research to understand the connection between air pollution and dementia better.

The London study looked at 130,978 adults, ages 50 to 79, who were registered in 2005 with 75 primary care practices located within the London orbital M25 motorway.

Alzheimer's Research UK described the study as a "growing area of research", but chief scientific officer Dr David Reynolds added: "While the researchers tried to account for factors like wealth, heart disease and other potential explanations for differences in dementia rates across the capital, it is hard to rule out other explanations for the findings". Over an average of 7 years, 2,181 patients (1.7%) were diagnosed with dementia, including Alzheimer's disease.

"These results are not surprising and coincide with larger epidemiological studies establishing robust associations between incident cases of dementia and increases in fine particulate matter, and living less than 50 meters from major traffic roads", Lilian Calderon-Garciduenas, MD, PhD, of the University of Montana in Missoula, who was not involved in the study, toldMedPage Today. This study adds to this body of evidence and fits with some of the previous studies.

Another study, published last month in the Proceedings of the National Academy of Sciences, found that long-term exposure to air pollution in China can impede cognitive performance in verbal and math tests.

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The European Environment Agency estimates that more than 400,000 people in Europe's urban areas die prematurely every year due to outdoor air pollution.

And even if the impact of air pollution remains relatively modest, they added, "the public health gains would be significant if it emerged that curbing exposure might delay progression of dementia". He noted that other research has suggested that children's brain development may be affected by pollution.

Campaigners called on the government to take urgent action on air pollution.

The second most common form of dementia is called vascular dementia. In the United Kingdom, there are about 850,000 people living with dementia, according to the UK-based Alzheimer's Society. The health of people of all ages is at increased risk from breathing polluted air. Air pollution has been associated with heart disease and respiratory disease said Professor Frank Kelly, of environmental health at King's College London. Since road traffic is the leading cause of illness, advocates are pushing legislators to focus efforts on cleaning vehicle emissions to clean up the air.

A Defra spokesperson said levels of air pollution, including NOx, had fallen and the government was taking further action: "By ending the sale of conventional new diesel and petrol cars and vans by 2040, we are acting faster to tackle air pollution than nearly every other major developed economy".

Labour slammed ministers for failing to address air pollution, which regularly exceeds legal limits in many areas, particularly in London. "[We] would bring forward a new Clean Air Act and a network of clean air zones to tackle the UK's illegal levels of air pollution in the quickest time possible".

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