Study finds three biggest risk factors for dementia

 While there are a few risk factors for dementia that you can’t control — like age and family history — a growing body of research shows that there are several that can potentially be changed throughout life. And a new study suggests that three of these so-called modifiable risk factors may have a big impact on an aging brain.

Diabetes, alcohol consumption (measured by frequency) and exposure to air pollution are the most harmful modifiable risk factors for dementia out of 15 that were studied in a new report published in the journal Nature Communications. A team of researchers examined brain scans of nearly 40,000 UK Biobank participants and found that parts of the brain associated with Alzheimer’s disease, the most common form of dementia, that are more prone to earlier and accelerated aging were most affected by these three factors.

“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,” study coauthor Gwenaëlle Douaud, an associate professor at the University of Oxford, said in a statement.

Other known modifiable risk factors studied were blood pressure, cholesterol, weight, smoking, depression, inflammation, hearing, sleep, socialization, diet, physical activity and education.

A closer look at the big three

The study findings are not surprising, says Andrew Bender, a neuroimaging researcher at the Cleveland Clinic Lou Ruvo Center for Brain Health. 

Excessive alcohol use — defined as more than 21 drinks weekly — is among the 12 modifiable risk factors for dementia noted in a 2020 report published by the Lancet Commission. The Centers for Disease Control and Prevention (CDC) says that over time, too much alcohol can lead to learning and memory problems, including dementia.

And Bender, who was not involved in the latest study, says “diabetes is a really well studied and well known risk factor.” If diabetes is not well controlled and too much sugar remains in the blood, it can damage the organs over time, including the brain, explains the Alzheimer’s Association. High blood sugar is also linked to inflammation and cardiovascular disease — both of which can contribute to declining brain health.

Research on the health effects of air pollution is newer, but has been accumulating in recent years. A 2023 study published in JAMA Internal Medicinelooked at data from more than 27,000 adults older than 50 and found that those who went on to develop dementia were more likely to live in places with higher levels of fine particulate matter. This type of air pollution can come from vehicles and factories, though in this particular study, fine particulate matter from agriculture and wildfires was specifically associated with an increased risk of dementia. 

Another study published this year in the journal Neurology found that people with greater exposure to traffic-related air pollution were more likely to have high levels of amyloid plaques in their brains after they died. These plaques are a hallmark of Alzheimer’s disease.

Inflammation could help explain the emerging link between air pollution and brain health. Some animal studies suggest that “there is a relationship between particulate matter in pollution and inflammation in the brain,” Bender says. Researchers have also found that tiny pollution particles — the kind you might inhale from smoke or exhaust in the air — can circulate in the blood and work their way into the brain, where they may cause direct damage.

Managing your dementia risk

In the study, the researchers also looked at genetic factors that may be associated with dementia and other brain changes. Bender says this area of research could one day influence how we assess and manage our individual risks.

“I think that in time, we’ll likely have a more personalized approach for assessing risk for dementia that includes not just these modifiable factors, but how they may also interact with someone’s genetic profile,” Bender says. “We’re certainly not there yet, but it’s studies like this that help lead the way in providing the necessary information to translate these findings into something that can be clinically applied in the future.”

For now, he says, the takeaway is that individuals do have some control over their dementia risk. In fact, experts say that nearly 40 percent of dementia cases may be prevented or delayed with lifestyle and behavior changes.

Air pollution is a risk factor that’s less modifiable since many people are more restricted when it comes to choosing where they live or work. But others, such as alcohol intake and chronic health conditions like diabetes “are all really well established factors [for dementia] that are individually controllable,” Bender says. “In addition, other things like smoking, regular cardiovascular exercise, and [socialization] are all associated with reduced dementia outcomes.”