The negative effects of air pollution on human health have caused it to become a global issue of increasing concern. According to recent studies, dementia risk may indeed be higher when one is exposed to air pollution. The link between air pollution and dementia, however, is complicated and influenced by a number of variables, including genetics.
Researchers explain how exposure to ambient air pollution – including emissions from power plants and automobile exhaust – is linked to a measurably higher risk of dementia over time. An international study that was commissioned by the journal Lancet three years ago identified 12 modifiable risk factors for dementia, including three new ones: excessive alcohol use, head trauma, and air pollution.
Writing in the May 2, 2023 issue of the Journal of Alzheimer’s Disease, a team of researchers, led by scientists at the University of California San Diego, further elaborate on how exposure to the last of those new factors – ambient air pollution, such as car exhaust and power plant emissions – is associated with a measurably greater risk of developing dementia over time.
Our findings emphasize the importance of identifying modifiable risk factors as early as possible in life and that the processes by which air pollution affects risk of later-life cognitive decline begin earlier than previous studies suggest.
William S. Kremen
Senior author William S. Kremen, Ph.D., professor of psychiatry and co-director of the Center for Behavior Genetics of Aging at UC San Diego School of Medicine, and colleagues examined baseline cognitive assessments of approximately 1,100 men participating in the ongoing Vietnam Era Twin Study of Aging. The average baseline age was 56, with 12 years of follow-up.
They also assessed episodic memory, executive function, verbal fluency, brain processing speed, and APOE genotype, as well as exposure to specific matter (PM2.5) in the air and nitrogen dioxide (NO2), which is produced when fossil fuels are burned.
APOE is a gene that codes for a protein that is essential for the transport of cholesterol and other fats in the bloodstream. APOE-4, a variant or allele of APOE, has been identified as a strong risk factor gene for Alzheimer’s disease.
Researchers discovered that participants with higher levels of PM2.5 and NO2 exposure in their 40s and 50s had poorer cognitive functioning in verbal fluency from age 56 to 68. Persons carrying the APOE-4 allele appeared to be even more sensitive, with those exposed to higher PM2.5 levels performing worse in executive function and those exposed to higher NO2 levels performing worse in episodic memory.
The term “executive function” refers to higher-level cognitive abilities that are used to plan, control, and coordinate mental behaviors and acts. The ability to recall and relive distinct, specific past events is referred to as episodic memory.
“The 2020 Lancet report concluded that modifying 12 risk factors, which include others like education and depression in midlife, could reduce dementia incidence by as much as 40%,” said first author Carol E. Franz, Ph.D., professor of psychiatry and co-director of the Center for Behavior Genetics of Aging.
“According to the report, ambient air pollution is a greater risk factor for Alzheimer’s and related dementias than diabetes, physical activity, hypertension, alcohol consumption, and obesity.” Our findings emphasize the importance of identifying modifiable risk factors as early as possible in life – and that the processes by which air pollution affects risk of later-life cognitive decline begin earlier than previous studies suggest.”
