There are more than six million people living with dementia in the United States, but scientists are still trying to figure out how to lower the odds of experiencing poor brain health. New research suggests that avoiding three risk factors in middle age — high blood pressure, diabetes, and smoking — could give you 13 more dementia-free years later in life.
The research makes a case for continuing to focus on health in midlife and beyond. But it also helps people better understand their dementia risk, which is often broken down by the percentage of adults who develop cognitive issues such as memory loss.
“We wanted a measure people actually think in: years,” says Josef Coresh, MD, PhD, study coauthor and founding director of the Optimal Aging Institute at NYU Langone Health. “How many years of life can you expect to live with your mind intact?”
3 Factors Tied to Earlier Dementia Onset
Everyone involved in the study was dementia-free at the start. The researchers analyzed participants’ health data to look for three risk factors: high blood pressure, diabetes, and smoking. From there, the researchers followed the participants for an average of 26 years.
During the study period, about 3,000 participants developed dementia, and more than 5,000 died without developing dementia.
Researchers found that participants who had none of the risk factors lived without developing dementia for nearly 13 years longer than adults who had all three risk factors. That translated to 30 years of dementia-free life for those with no risk factors, compared with 17 years for those with three risk factors.
The findings don’t mean that everyone with these risk factors is bound to develop dementia eventually, but the odds go up with time, says Janet M. O’Mahony, MD, an internal medicine doctor at Mercy Medical Center in Maryland. “People who live long enough may develop dementia because it is more common in people in their eighties than people in their seventies, so long-livers are at risk,” she says. “On the other hand, healthier people are less prone to dementia, but are more likely to be long-livers. This is why they described it as dementia-free years of life.”
Dementia onset also varied by sex. Researchers found that women with all three risk factors lived an average of 18.1 years from the start of the study without developing dementia, compared with 16.6 years for men who met the same criteria.
White participants with all three risk factors lived an average of 19.6 more years without developing dementia, while Black participants with the same risk factors had 16 more years of dementia-free life.
The 3 Risk Factors Make Sense to Doctors
The brain is a vascular organ that uses about 20 percent of the blood pumped by the heart, according to Dr. Coresh. “It has almost no reserve; it can’t store fuel,” he says. “High blood pressure, diabetes, and smoking all damage the small vessels that supply it, through large and smaller silent strokes, white matter injury, reduced blood flow, and chronic inflammation.”
Injury to blood vessels makes it easier for harmful proteins to accumulate in the brain, like amyloid plaques and tau tangles linked to Alzheimer’s disease, he adds.
Scientists have already established that there’s a strong link between heart disease and dementia. Most recently, an analysis of 800,000 adults published in the Journal of the American Heart Association found that people with hypotension, or low blood pressure, were about three times more likely to develop Alzheimer’s disease, compared with those without low blood pressure. Adults with high blood pressure were about 1.6 times more likely to be diagnosed with Alzheimer’s disease, compared with those without.
“It is assumed that controlling [these factors] will diminish the likelihood of developing cardiovascular disease, but also dementia,” says Jonathan Moray, MD, a neurologist at Tufts Medicine Lowell General Hospital in Massachusetts. “So keeping your blood pressure normal, avoiding diabetes, and not smoking reduces the cardiovascular damage that is itself tied to dementia onset, buying you more years to live free of the disease.”
Coresh notes that focusing on these three risk factors can yield significant health benefits. “These are the same conditions that cause the heart attacks and strokes that end people’s lives in their sixties and seventies,” he says. “So good vascular health buys you two things at once: more years, and better brain years within them.”
Still, dementia is a complex condition, making it hard to say that controlling these three lifestyle factors will eliminate risk, points out Amalia Peterson, MD, a behavioral neurologist and assistant professor of neurology at Vanderbilt University Medical Center in Nashville, Tennessee.
“For a majority of people, Alzheimer’s disease and related dementias are the result of a combination of genetics and the environment,” she says. “This study highlights the importance of the environment, but there are still genetic factors that are outside of people’s control.”
The Study Has a Few Strengths and Limitations
The researchers looked at a large, diverse group of patients with decades of follow-up data. But they only looked at risk factors at a single point in time, rather than tracking participants’ health in relation to those factors over time.
Dementia assessments might also have differed between participants who recently went to the doctor and those who did not. Testing for cognition and dementia often requires comprehensive exams that may not have been performed during those routine visits.
Finally, the study is observational, making it difficult to say that having high blood pressure, diabetes, or smoking actually causes dementia or whether there are other influences.
The Best Way to Lower Your Dementia Risk, According to Doctors
Doctors agree that doing your best to manage blood pressure and diabetes risk and avoiding smoking are all important for lowering dementia risk.
Coresh also recommends focusing on healthy diet choices, movement, sleep, weight, and cholesterol, noting that he chose to study other risk factors that were easy to classify as a “yes” or “no” and could be prevented and addressed after they happened.
Dr. Peterson stresses the importance of staying on top of your health. “What is good for your heart is good for your brain,” she says. “I advise patients to follow up with their primary care physician to make sure that their blood pressure and cholesterol are under good control, that they monitor for diabetes and treat if they have it, and to not smoke.”
Overall, Coresh says that the findings should encourage people in midlife to change their health habits where they can. “It’s never too early, and it’s never too late,” he says.
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