Air pollution has longed been linked to poor health outcomes, but in a report released Tuesday from a team of researchers led by scientists at UC San Diego, it was also said to create a significantly greater risk of dementia.
Three years ago, an international study commissioned by the journal Lancet listed 12 modifiable factors that increased the risk of dementia, including three new ones: excessive alcohol, head injury and air pollution.
The scientists monitored the impact of ambient air pollution -- such as car exhaust and power plant emissions -- on around 1,100 men participating in the ongoing Vietnam Era Twin Study of Aging.
Senior author William Kremen, professor of psychiatry and co-director of the Center for Behavior Genetics of Aging at the UCSD School of Medicine, and colleagues studied the men with a baseline age of 56, with 12 years of follow-up.
Get top local stories in Southern California delivered to you every morning. Sign up for NBC LA's News Headlines newsletter.
The researchers additionally looked at measures of exposure to particular matter in the air and nitrogen dioxide, which is created when fossil fuels are burned, and "assessments of episodic memory, executive function, verbal fluency, brain processing speed" and a genotype that provides instructions for making a protein crucial to the transport of cholesterol and other fats in the bloodstream.
The genotype -- known as APOE -- has a version called APOE-4 that has been identified as a strong risk factor gene for Alzheimer's disease.
Researchers found that participants with higher levels of exposure to air pollution in their 40s and 50s displayed worse cognitive functioning in verbal fluency from age 56 to 68. And persons with APOE-4 appeared even more sensitive.
"The 2020 Lancet report concluded that modifying 12 risk factors, which include others like education and depression at midlife, could reduce dementia incidence by as much as 40%," said first author Carol Franz, professor of psychiatry and co-director of UCSD's Center for Behavior Genetics of Aging. "That report placed ambient air pollution as a greater risk for Alzheimer's and related dementias than diabetes, physical activity, hypertension, alcohol consumption and obesity."
"Our findings underscore the importance of identifying modifiable risk factors as early in life as possible -- and that the processes by which air pollution affects risk for later-life cognitive decline begins earlier than previous studies suggest," she said.
