Nothing’s simple when it comes to dementia, which appears to be influenced by both genetic and modifiable risk factors. But a new study finds a “weak spot” in the brain — a network of higher-order regions that develop later and can degenerate earlier than other regions — that are vulnerable to both schizophrenia and Alzheimer’s disease.
Of a list of 161 modifiable risk factors for dementia, three seem to hit that region the hardest, increasing risk of dementia: diabetes, air pollution and alcohol consumption. Those are also implicated in cardiovascular deaths and Parkinson’s disease, according to a new study published in the journal Nature Communications.
For the study, the researchers looked at brain scans of 40,000 individuals between the ages of 44 and 82 who were part of the UK Biobank database. Then they compared the images to their list of risk factors, which they broke into 15 bigger categories, including blood pressure, cholesterol, diabetes, weight, alcohol consumption, smoking, depression, inflammation, pollution, hearing, sleep, social aspects of life, diet, physical activity and education attainment.
A news release from University of Oxford quoted Gwenaëlle Douaud, who led the study: “We know that a constellation of brain regions degenerates earlier in aging, and in this new study we have shown that these specific parts of the brain are most vulnerable to diabetes, traffic-related air pollution — increasingly a major player in dementia — and alcohol, of all the common risk factors for dementia.”
The researchers point out that the three factors may be the most harmful, but the others have a negative effect, as well. Diabetes, air pollution and alcohol intake have twice the impact of other leading factors, followed by sleep issues, excess weight, smoking and high blood pressure.
The Washington Post reported that the researchers were not able to compare the genetic and modifiable risk factors with each other.
“What makes this study special is that we examined the unique contribution of each modifiable risk factor by looking at all of them together to assess the resulting degeneration of this particular brain ‘weak spot.’ It is with this kind of comprehensive, holistic approach — and once we had taken into account the effects of age and sex — that three emerged as the most harmful: diabetes, air pollution, and alcohol,” said Anderson Winkler, a co-author from the National Institutes of Health and a professor at University of Texas Rio Grande Valley, per the release.
What is dementia?
The Alzheimer’s Association calls dementia a “general term for loss of memory, language, problem-solving and other thinking abilities that are severe enough to interfere with daily life.”
Dementia is not a disease, but rather a group of symptoms. The group says about 7 million Americans have Alzheimer’s, which is the most common form of dementia. But as the number of cases increase due to the population getting older, the share of the population who has it is actually going down.
The findings are not entirely new. In 2020, a study in The Lancet reported that the age-specific incident of dementia decreased in some parts of the world, probably due to more education, better nutrition, access to health care and lifestyle changes. But there were common factors that increased risk.
The 2017 Lancet Commission had already noted a number of those, including: “less education, hypertension, hearing impairment, smoking, obesity, depression, physical inactivity, diabetes, and low social contact. We now add three more risk factors for dementia with newer, convincing evidence. These factors are excessive alcohol consumption, traumatic brain injury and air pollution,” those researchers wrote.
Per the Post article, “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.”
More dementia news
Also this week, a new study from University of California Davis Health reported that human brains are getting bigger, noting that the brains of people born in the 1970s are 6.6% larger by volume and 15% larger in terms of brain surface compared to the brains of folks born in the 1930s.
The findings were published in JAMA Neurology.
The researchers theorize that bigger brains means bigger brain reserve, potentially reducing risk of age-related dementia.
“Genetics plays a major role in determining brain size, but our findings indicate external influences — such as health, social, cultural and educational factors — may also play a role,” Charles DeCarli, the study’s first author, a professor of neurology who directs the UC Davis Alzheimer’s Disease Research Center, said in a written statement.
The findings are based on brain imaging of participants in the Framingham Heart Study, which has been ongoing for decades and now involves a second and third generation of participants. Between 1999 and 2019, 3,226 participants born in the 1930s through the 1970s had MRIs done. The average age at the time of the scan was 57.
There’s also reason to believe that more modern lifestyles have increased the risk of dementia, lending further credence to the role of modifiable lifestyle-related risk factors.
The University of Southern California this week had a study published in the Journal of Alzheimer’s Disease that “bolsters the idea that Alzheimer’s disease and related dementias are diseases of modern environments and lifestyles, with sedentary behavior and exposure to air pollution largely to blame,” per an article on SciTech Daily. The author wrote that there’s no evidence that dementia was a problem in ancient Rome and Greece.
