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Alzheimer's and Air Quality

Delivered February 4, 2020. Contributor: Kiersten M.

Goals

To understand any connection which might exist between air pollution and Alzheimer's, including any evidence that climate change could lead to an increase in the number of patients being diagnosed with dementia and/or Alzheimer's.

Early Findings

  •  A recent study conducted in London and published in BMJ has found that there is a positive correlation between decreased air quality and the incidence of dementia.
  • The study looked at adults between the ages of 50 and 79 and with no prior diagnosis or symptoms of dementia or Alzheimer's. The researchers "found evidence of a positive association between residential levels of air pollution across London and being diagnosed with dementia, which is unexplained by known confounding factors".
  • "Taking the data further, researchers attempted to quantify how much air pollution can raise the risk of dementia. To do this, they assumed what would happen if all patients in the study have been exposed at the levels associated with the bottom 20 percent, finding the difference to be seven percent."
  •  A 2018 study published in Medical News Today "suggests that people with the most exposure to top air pollutants have a higher risk of dementia, while another went as far as to argue that poor air quality causes around a fifth of dementia cases".
  • Another research study - published in 2019 in Brain - found that the reason poor air quality contributes to Alzheimer's and dementia incidence rates is because of PM2.5 particles, which are "tiny pollutants measuring about one-thirtieth of the width of a human hair. They enter ambient air through traffic exhaust fumes and smoke. Because PM2.5 particles can remain airborne for a long time, they are easily inhalable, which means that they can accumulate in unhealthful amounts in people's bodies — including inside the brain".
  • This study "found that the higher a person's exposure to fine particle pollution, the likelier they were to experience cognitive function impairments, such as problems with memory".
  • Other studies, including ones on both mice and dogs, have found a positive correlation between poor air quality and brain health in animals. "Studies of mice and dogs living in polluted areas suggest that air pollution could be associated with cognitive impairment. Exposure of mice and rats to traffic pollution in the lab resulted symptoms such as poorer learning ability, memory and motor skills."
  •  In 2016, a study in Canada looked at more than six million people and found that "those living within 50 metres of a major road were 7 percent more likely to develop dementia than people living more than 300 meters away, where fine particulate matter levels can be up to 10 times lower".

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