Air Pollution May Be Linked to Alzheimer’s

According to brain scans of many seniors, evidence shows that people who live in areas with poor air conditions may have a higher chance of amyloid plaques.

Living with pollution from cars, factories, power plants, and forest fires may add to your risk of Alzheimer's disease — along with smoking, diabetes, drinking too much alcohol, and traumatic brain injury.

Researchers at the University of California in San Francisco looked at brain scans of more than 18,000 seniors, with an average age of 75. All were diagnosed with mild cognitive impairment or dementia — although 40 percent of the brain scans did not show any amyloid plaques, a sign of Alzheimer’s.

Some of the volunteers may instead have had another kind of dementia. The volunteers lived around the country. When the researchers compared the scans of people living in the most polluted zip codes to those of volunteers in the least polluted, the first group had a 10 percent higher chance of amyloid plaques.

More than 6 million people over 65 in the United States have Alzheimer's disease. Based on the numbers in the research, exposure to air pollution may be part of the problem for tens of thousands. The exposure that seemed to trigger the plaques was close to annual averages in San Francisco, the researchers noted.

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The team estimated air pollution in the neighborhood of each participant, using Environmental Protection Agency data that measured ground-level ozone and PM2.5, fine, inhalable particles with a diameter of less than 2.5 micrometers. The team also divided locations into groups, according to the concentration of PM2.5, which limit visibility and cause air to appear hazy.

It found that the probability of a positive PET scan rose progressively as concentrations of pollutants increased, corresponding with a difference of 10 percent probability between the least and most polluted areas.

"Exposure in our daily lives to PM2.5, even at levels that would be considered normal, could contribute to induce a chronic inflammatory response," said first author Leonardo Iaccarino, PhD, from the University of California, San Francisco Memory and Aging Center, Department of Neurology, and the Weill Institute of Neurosciences. "Over time, this could impact brain health in a number of ways, including contributing to an accumulation of amyloid plaques."

Bad air is bad for you

Ever since the Great Smog in London in 1952, researchers have documented that exposure to polluted air is linked to heart and lung disease and death. The study adds to a growing body of research that ties air pollution to both dementia and Parkinson's disease. One study, for example, claimed to estimate how much extra black carbon exposure from traffic accelerated aging-related cognitive decline by two years in men.

Other studies have linked air pollution to bad effects on the cognition of children, affecting even unborn babies through pregnant women.

The study is the first to include people with mild cognitive impairment, which often comes before a dementia diagnosis.

What you can do

If you live in a polluted area and have Alzheimer’s in your family or are experiencing mild cognitive impairment, take precautions.

For example, if your area is full of wildfire smoke, stay indoors. Close your windows and doors tight and seal any air leaks. Masking tape works. Use an air purifier indoors. Use a vacuum with a HEPA filter.

Healthy habits may help delay Alzheimer's symptoms. Aim for 30 minutes of moderately vigorous aerobic exercise, three to four days a week.

The Mediterranean diet helps. Cut way back on red meat and favor fish and some chicken. For other protein sources, consume nuts, dairy, and legumes. Use olive oil and eat plenty of vegetables.

You also should get enough sleep.

The evidence is weaker that learning new things will put off dementia, but it could improve your zest for life. Socializing may also help.

The good news: Dementia isn't increasing as fast as expected as the world’s population gets older. In a study of nearly 50,000 seniors over 25 years, researchers found that the percentage with the disease adjusted for age has dropped in each of the past three decades.

The authors noted that in China and Nigeria, the percentages have stayed stable or increased, and the evidence is mixed for minorities in the United States. Air pollution is part of that story. China, Nigeria, and the United States are in the top 10 countries globally for the number of premature deaths linked to air pollution.

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