Study finds 3 big risk factors for dementia

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Diabetes, air pollution and alcohol consumption could be the biggest risk factors for dementia, a study has found.

Researchers compared modifiable risk factors for dementia — which is characterized by the impairment of memory, thinking and reasoning — and studied how these factors appear to affect certain brain regions that are already particularly vulnerable to Alzheimer's disease and schizophrenia.

The research, based on brain scans of nearly 40,000 adults, between ages 44 and 82, in Britain was published Wednesday in Nature Communications.

These vulnerable regions of the brain develop during adolescence and help the brain process and integrate "bits of information across different modalities, across different senses," said Gwenaëlle Douaud, an associate professor at the University of Oxford and co-author of the study. But "they're the first ones to go when we start aging."

"What we're trying to do is say: What are the common risk factors for dementia that are affecting these regions?" Douaud said. "These are the three most harmful but then, obviously, the others, they have an effect."

• Researchers investigated the genetic and modifiable risk factors that contribute to the vulnerability of the "most fragile parts of the brain" by studying the brain scans of nearly 40,000 relatively healthy participants from the U.K. Biobank.
• The study examined 161 modifiable risk factors, including blood pressure, cholesterol, diabetes, weight, alcohol consumption, smoking, mood, inflammation, pollution, hearing, sleep, socialization, diet, physical activity and education.
• A diagnosis of diabetes, the amount of nitrogen dioxide in the air and how often someone drinks alcohol — from never to daily, or nearly every day — were found to be the three most detrimental risk factors to these regions of the brain, Douaud said.
• Diabetes, air pollution and alcohol consumption each has an effect that is about twice as much as the other leading risk factors, Douaud said. The next major risk factors are sleep, weight, smoking and blood pressure.
• Researchers identified seven genetic clusters that affect these vulnerable parts of the brain, some of which are also associated with Parkinson's and Alzheimer's diseases. Douaud said the genetic and modifiable risk factors are not comparable.

More than 55 million people live with dementia around the world, and that figure is expected to increase to 153 million by 2050, according to the World Health Organization.

Dementia is the loss of cognitive function, and symptoms result from brain neurons losing their connection to other brain cells and eventually dying, according to the National Institute on Aging. Everyone loses neurons over time, but the loss is more significant in dementia patients.

Diabetes and alcohol consumption "have been consistently shown to be associated with both cerebral and cognitive decline," the researchers wrote in the Nature Communications study. And there is growing evidence that exposure to air pollution is a risk factor for cognitive decline and dementia.

A 2020 Lancet report on dementia found that a dozen modifiable risk factors such as hypertension, hearing impairment, smoking and obesity together account for up to 40 percent of dementia cases worldwide.

A person's age, genes, family history, a traumatic brain injury or a stroke also are potential risk factors.

Gill Livingston, a professor of psychiatry of older people at University College London and the lead author of the 2020 Lancet report, said that the new study was "very interesting" but that the participants in the U.K. Biobank are a "much healthier" and highly motivated group. The findings may not be applicable to a broader population.

Still, they show that people can make decisions to reduce their risk of cognitive decline as they age, Livingston said.

"There's quite a lot people can do in their everyday life to maintain cognitive health," she said. "This just reinforces it."

Try to eat a healthy, varied diet to help lower your blood sugar, take measures to protect against "traffic-related pollution" and drink alcohol in moderation, Douaud said in an email.

"Of course, some of these should not only be down to individuals, and the burden should also be shared with (local) governments devising helpful policies," she said.

Livingston said social and physical activity — talking with friends and exercising — "make a huge difference." And stimulating experiences, walking outside, "seeing different things" can be beneficial, she said.

Hearing loss, which is more likely as a person ages, can take away opportunities for conversations that lead to "rapid brain stimulation," Livingston said.

"And if you smoke, stop," she said.

Marlene Cimons contributed to this report.