Many studies have pointed to the links between diabetes and an increased risk of dementia. Experts say it is likely because diabetes can harm the disease brain in various ways.
Now, new findings suggest that young people with diabetes may be at special risk along the way.
At age 70, according to the study, people who had recently been diagnosed with type 2 diabetes did not have a higher risk of dementia than people without diabetes. The picture was different for people who had been diagnosed more than ten years earlier: they had twice the risk of dementia than people without a diabetic age of their age.
This may be simply because they have been living with diabetes for years.
“Younger age at the onset of diabetes implies a longer duration, which allows all the adverse effects of diabetes to develop over a longer period,” said senior researcher Archana Singh-Manoux. She is a research professor at the University of Paris and at the French national institute of health INSERM.
Type 2 diabetes arises when the body loses sensitivity insulin, a hormone that regulates blood sugar. This causes a chronic rise in blood sugar, which over time can damage large and small blood vessels throughout the body.
These effects, which can affect blood flow to the brain, are one of the reasons diabetes is linked to dementia, Singh-Manoux said.
He also pointed to other potential pathways: insulin plays a role in brain function and diabetes can prevent it from doing its job. Meanwhile, treatment for diabetes can cause frequent episodes of low blood sugar, which for long periods can also harm the brain, Singh-Manoux said.
The findings, published on April 27 in Journal of the American Medical Association, have broad implications for public health.
In the United States alone, more than 34 million people have diabetes, and the vast majority have type 2 diabetes, according to the American Diabetes Association.
At the same time, type 2 diabetes was a disease of older adults. But with the growing prevalence of obesity, a major risk factor for type 2 diabetes, the disease is increasingly being diagnosed in young people.
“The prevalence of diabetes continues to rise,” Singh-Manoux said, “and the age at the beginning is getting younger.”
This means that more people will live longer with diabetes and will be vulnerable to the complications of the disease. It is already known that younger people are when diabetes arises, the higher the risk of heart disease, stroke and premature death, Singh-Manoux said.
This study adds dementia to that list, he said.
The research included more than 10,000 adults in the UK who were between the ages of 35 and 55 in the early 1980s. Over the next three decades, 1,710 people developed type 2 diabetes, while 639 were diagnosed with dementia.
At age 70, people who had developed diabetes over the past five years had no higher risk of dementia than people without diabetes.
But those who had been diagnosed more than ten years earlier showed a double in their risk of dementia. The actual rate of brain disease was 18 cases per 1,000 people each year, compared with nine cases per 1,000 in adults without diabetes.
Overall, the risk of dementia at age 70 increased by 24% for every five years people had lived with diabetes.
This is not a surprising finding, according to Dr. Medha Munshi, who runs the geriatric diabetes program at the Joslin Diabetes Center in Boston.
On the other hand, Munshi said, there is “some peace of mind” in the lack of additional risk among seniors recently diagnosed with diabetes.
The question is: can young patients with diabetes curb the risk of dementia by achieving better blood sugar control?
Other studies, Singh-Manoux said, have found that people with well-controlled diabetes have a slower mental decline than those with poor control. And in this study, he noted, the risk of dementia was particularly high among patients with diabetes who also developed heart disease.
What is key, Munshi said, is that prevention begins soon.
“People in their forties and fifties aren’t usually worried about dementia,” he said. “But this is the time to try to avoid it.”
Diabetes control often means taking medication or insulin, along with changes in diet and regular exercise, which, according to Munshi, can have numerous long-term health benefits.
“What we do at a younger and middle age will change the way we end up in old age,” he said.
The American Diabetes Association has more benefits manage type 2 diabetes.
SOURCES: Archana Singh-Manoux, PhD, Research Professor, University of Paris, INSERM, Paris; Medha Munshi, MD, director of the geriatric diabetes program at the Joslin Diabetes Center and associate professor of medicine at Harvard Medical School in Boston; Journal of the American Medical Association, April 27, 2021