The findings, however, highlight that physical activity, abstention from smoking, and avoiding heavy alcohol consumption could help keep brains young.

Elevated Blood Sugar Could Add Years to Brain Age

For the analysis, the researchers referred to medical information from more than 31,000 dementia-free adults from the UK Biobank, which included measures of cardiometabolic risk factors (obesity, hypertension, and cholesterol) as well as lifestyle behaviors like smoking, drinking, and physical activity.

According to the data, 53 percent had normal blood glucose, 43 percent were considered prediabetic, and 4 percent had type 2 diabetes.

By using a machine learning model, the researchers were able to estimate brain age in relation to a patient’s chronological age.

The results, published this week in the journal Diabetes Care, showed that type 2 diabetes was associated with brains that were 2.3 years older than their chronological age, while prediabetes increased brain aging by about four months. 

The researchers further noted that the brains of individuals with poorly controlled diabetes appeared more than four years older than their chronological age.

When they reviewed a subset of about 2,400 patients who underwent up to two MRIs over a follow-up of 11 years, researchers observed a slight increase in brain aging over time in patients with diabetes — just over three months annually.

“This study shows that even slightly high glucose levels — that aren't considered high enough to be diabetes but are consistent with prediabetes — can affect the brain and cause the brain to age more rapidly,” says Susan Elizabeth Spratt, MD, a professor of medicine at Duke University in Durham, North Carolina, with a specialty in endocrinology, metabolism, and nutrition, who was not involved in the current research.

What Magnetic Resonance Imaging Reveals

Through the use of MRIs, scientists captured measures such as brain volume, thickness of the cortex (also called gray matter, or the brain's outermost layer of nerve cell tissue), and degradation of white matter (networks of nerve fibers in the brain).

While this type of imaging may give detailed insight into brain aging for research, it may not be practical for evaluating cognition, according to Ajaykumar D. Rao, MD, the chief of the section of endocrinology, diabetes, and metabolism at the Lewis Katz School of Medicine at Temple University in Philadelphia, who was not involved in the study.

“We can't be subjecting all those living with prediabetes and diabetes to multiple MRIs — they may not be clinically meaningful,” says Dr. Rao, who was not involved in the study. “I think it's important for those patients to meet with their primary care teams and discuss whether they should undergo neurocognitive testing.”

How Healthy Living Helps

On the positive side, the study authors found that certain lifestyle habits significantly reduced the chances of rapid brain aging.

For Thomas Vidic, MD, an adjunct clinical professor of neurology at Indiana University School of Medicine at South Bend and a practicing physician at the Elkhart Clinic, the results were not surprising, since diabetes causes vascular disease and inflammation, and those factors can affect blood supply to the brain and affect brain tissue. Exercise, on the other hand, can improve blood flow to the brain. He further stresses that alcohol and smoking can be toxic to brain cells, while abstention protects them.

“Brain health is a lifelong process, and we need to take care of all aspects of brain health throughout our lifetime,” says Dr. Vidic, who is also a fellow of the American Academy of Neurology and not an author of the new study. “It's not one of those things that you turn 65 and say, ‘I need to get started on this.’”