Alzheimer’s disease and related dementias impact approximately seven million Americans, but scientists are still investigating what causes the condition — and how to prevent it.
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Now, new research suggests that poorly controlled blood sugar may play a role.The study, published in the journal Diabetes, Obesity, and Metabolism, found a link between higher blood sugar spikes after meals and a greater risk of developing Alzheimer’s disease.
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“We are slowly piecing together the mechanism that links [blood sugar] to brain health,” says Andrew Mason, PhD, lead study author and a researcher at the University of Liverpool.
“Our research suggests that keeping blood sugar stable may be good not only for diabetes prevention, but also for brain health in the longer term,” adds Vicky Garfield, PhD, a study coauthor and genetic epidemiologist also at the University of Liverpool in England.
Genetic Analysis Linked Blood Sugar Spikes to Alzheimer’s Risk
For the study, researchers analyzed genetic data from more than 350,000 people between the ages of 40 and 69 who participated in the UK Biobank, a long-term biomedical database.
The researchers zeroed in on markers of how the body processes sugar, specifically looking at genes related to:
- Fasting glucose, or blood sugar levels when someone hasn’t eaten for at least eight hours
- Insulin, a hormone naturally produced by the pancreas that helps the body move sugar from the blood into cells for energy
- Blood sugar levels two hours after eating
The researchers then used a technique called Mendelian randomization to see whether these factors were likely to play a role in dementia risk.
The analysis suggested that people with a lifelong predisposition to higher glucose levels two hours after eating had a 69 percent higher relative risk of developing Alzheimer’s dementia compared with those who don’t have the genetic risk, Dr. Garfield explains.
“But it doesn’t mean 69 out of 100 [people] will get Alzheimer’s — the actual risk still depends on age and other factors,” she says.
For example, if a person’s baseline risk of developing Alzheimer’s disease over the next 10 years is 5 percent, a 69 percent relative increase would raise it to 8.5 percent.
If a person’s baseline lifetime risk is 20 percent, having this genetic profile would raise the absolute risk to about 34 percent, Garfield says.
“We can’t derive these absolute numbers from the Mendelian randomization analysis alone, unfortunately,” she adds.
In the United States, the lifetime risk for developing Alzheimer’s disease is 1 in 5 for women and 1 in 10 for men.
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There Is an Existing Link Between Diabetes and Dementia
Diabetes describes a number of conditions where the body has a hard time processing blood sugar. Poorly managed diabetes has long been implicated in the development of Alzheimer’s, Dr. Masons says, “and this is yet more evidence of a causal genetic link between an individual’s metabolism and Alzheimer’s.”
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Earlier research found that up to 81 percent of people living with Alzheimer’s disease also have type 2 diabetes.
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There are several reasons for this link, say Cathryn Devons, MD, chief of geriatrics at Northwell’s Phelps Hospital in Sleepy Hollow, New York. “High blood sugars are linked to oxidative stress and damage to the blood vessels to the brain,” she says.
Insulin resistance — when the body doesn’t respond as well to the hormone that escorts blood sugar to cells — is also linked to a buildup of amyloid plaques in the brain, a marker of Alzheimer’s disease, Dr. Devons adds.
“When your blood sugar gets high, parts of your body are unable to get blood, and many parts of your body start being affected, including your brain, in addition to your heart, kidneys, nerves, and eyes,” says Clifford Segil, DO, a neurologist at Providence Saint John’s Health Center in Santa Monica, California.
Another Reason to Get Prediabetes Under Control
The findings emphasize the importance of blood sugar management in people with diabetes, Devons says. “Working with your doctor to monitor blood sugar carefully through diet, exercise, and medication is essential,” she says.
If you have prediabetes (high blood sugar that hasn’t yet become diabetes), Devons recommends talking to your healthcare provider about diet and exercise changes you can make to lower the risk your condition will progress to diabetes. “Good glucose control is one way to lower risk of cognitive decline with aging,” Devons says.
