Cars and fires join the list of Alzheimer’s risk factors

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The higher the air pollution, the higher the probability of amyloid plaques

A new study led by researchers at the University of California, San Francisco has found that among older Americans with cognitive impairment, the higher the air pollution in their neighborhood, the greater the likelihood of amyloid plaques, a hallmark of the disease. of Alzheimer.

The study, published in the journal JAMA Neurology, adds to a body of evidence indicating that pollution from cars, factories, power plants, and wildfires adds to established dementia risk factors such as smoking and diabetes.

The researchers looked at the positron emission scans of more than 18,000 older people whose average age was 75 with dementia or mild cognitive impairment and who lived in zip codes across the nation. They found that those in the most contaminated areas were 10% more likely that a PET scan would show amyloid plaques, compared to those in the least contaminated areas.

“This study provides additional evidence to a growing and convergent literature, ranging from animal models to epidemiological studies, that suggests that air pollution is a significant risk factor for Alzheimer’s disease and dementia,” says lead author Gil Rabinovici, UCSF Memory and Aging Center, Department of Neurology and the Weill Institute of Neurosciences.

The 18,178 participants had been recruited for the IDEAS (Imaging Dementia – Evidence for Amyloid Scanning) study, which had enrolled Medicare beneficiaries whose mild cognitive impairment or dementia had been diagnosed after a comprehensive evaluation.

It was later found that not all participants had positive PET scans: 40% showed no evidence of plaques on the scan, suggesting diagnoses other than Alzheimer’s, such as frontotemporal or vascular dementias, that are not associated with telltale amyloid plaques.

Air pollution in the neighborhood

Air pollution in each participant’s neighborhood was estimated with data from the Environmental Protection Agency that measured ground-level ozone and PM2.5, atmospheric particulate material that has a diameter of fewer than 2.5 micrometers.
The researchers also divided the locations into quartiles based on the concentration of PM2.5. They found that the probability of a positive PET scan progressively increased as contaminant concentrations increased, and predicted a 10% probability difference between the least and most contaminated areas.

“Exposure in our daily life to PM2.5, even at levels that would be considered normal, could contribute to inducing a chronic inflammatory response,” says first author Leonardo Iaccarino, also from the UCSF Memory and Aging Center, Department of Neurology and the Weill Institute for Neuroscience – Over time, this could affect brain health in a number of ways, including contributing to the build-up of amyloid plaques. “

Overall PM2.5 concentrations would not be considered too high to have a significant association with amyloid plaques, which is equivalent to annual averages in San Francisco during the time of the study, Rabinovici adds.

“I think it’s very appropriate that air pollution has been added to the modifiable risk factors highlighted by the Lancet Commission on dementia,” he acknowledges, referring to the magazine’s decision this year to include air pollution, along with binge drinking and traumatic brain injury, to your list of risk factors.

The study complements previous large-scale studies linking air pollution to dementia and Parkinson’s disease and adds novel findings by including a cohort with mild cognitive impairment, a frequent precursor to dementia, and using amyloid plaques as a biomarker of the illness.

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