Air Pollution Linked to Higher Risk of Dementia

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A study has found evidence that even slightly higher levels of air pollution can significantly increase a person’s risk of dementia.

Researchers at the Washington University recruited more than 4,000 Seattle-area residents in a long-running dementia study. The participants were part of the Adult Changes in Thought (ACT) Study that began in 1994. Around 1000 of these people received a dementia diagnosis over the course of the study. The team at Washington aimed to analyze the risk factors of dementia in the recruited participants. They then conducted an analysis combining data from this study, and another that began in 1970 and measured air pollution levels in the area. The researchers aimed to evaluate the link between the risk of dementia and levels of particulate matter. The results of the study are available in the journal Environmental Health Perspectives.

Dementia is a major cause of disability among older people around the world. According to the World Health Organization, 50 million people worldwide have dementia. Over the years, researchers have discovered multiple risk factors for the disease. These range from increasing age to lack of sleep and even social isolation. Moreover, there is currently no effective treatment that can cure or alter the disease’s progression. In 2016, dementia was the fifth leading cause of death around the world. Therefore, the focus has now shifted to addressing modifiable risk factors of dementia in an effort to reduce the disease burden.

Several studies have implicated air pollution as a possible cause of dementia. However, along with other limitations, most of these studies include a short follow-up period of 5 years or less.

How we’ve understood the role of air pollution exposure on health has evolved from first thinking it was pretty much limited to respiratory problems, then that it also has cardiovascular effects, and now there’s evidence of its effects on the brain.

Professor Lianne Sheppard, senior author

Particulate Matter and the Brain

In an effort to address the limitations of previous studies, researchers at Washington conducted a population-based study looking at 10-year average fine particulate matter exposure. Once a person received a dementia diagnosis, researchers analyzed average air pollution exposure of the participant. They then compared the levels to other participants. Thus, finding the effect of varying air pollution levels and their contribution to the development of dementia.

The results showed that just a 1 microgram per cubic meter increase in exposure resulted in a 16% greater risk of dementia. This puts into perspective the neurodegenerative effect even a small increase in air pollution can have on a population.

We found that an increase of 1 microgram per cubic meter of exposure corresponded to a 16 percent greater hazard of all-cause dementia. There was a similar association for Alzheimer’s-type dementia.

Rachel Shaffer, lead author

Although individuals can take measures to reduce their exposure, the ultimate responsibility lies with a city’s ruling body and its policies.


Shaffer, Rachel M., et al. “Fine Particulate Matter and Dementia Incidence in the Adult Changes in Thought Study.” Environmental Health Perspectives, vol. 129, no. 8, 2021, p. 087001., doi:10.1289/ehp9018.


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