Type 2 diabetes has been previously linked to memory and thinking problems. A new study published on May 24, 2022, in the medical journal eLife, suggests that the reason behind this is that type 2 diabetes makes the human brain age faster. The study findings add to a body of research on diabetes and brain health which includes several studies linking type 2 diabetes to a swifter decline in mental sharpness, and an increasingly higher risk of dementia.
In type 2 diabetes, the human body cannot use the insulin hormone effectively, which leads to poor peripheral utilization of glucose (sugar) by the body tissues and organs. This increases blood sugar levels which causes vascular damage and neuronal injuries throughout the human body. Individuals with type 2 diabetes are at risk of adverse complications such as cardiovascular disease, stroke, and kidney disease. But the diabetes connection with the brain is beyond that.
After analyzing data from 20,000 individuals aged 50 to 80 years, researchers found that individuals with type 2 diabetes generally performed worse on tests of thinking skills and memory skills compared to individuals without diabetes. The result was from past studies.
The study participants were a part of an ongoing research project called the United Kingdom (UK) Biobank. In this project, the researchers performed standard tests of cognitive abilities such as memory, information processing speed, and executive function involving planning and organization skills essential for accomplishing daily tasks. In addition, a smaller group also underwent magnetic resonance imaging (MRI) for the brain.
The study findings showed that on average, type 2 diabetics scored lower on the cognitive tests, than non-diabetic individuals matched for age, sex, and educational level with 13% lower executive function scores, and 7% lower processing speed.
It is a well-established fact that brain tissue gradually shrinks as we age, with certain areas withering to a higher extent and more rapidly than others. MRI scans reveal several alterations in the regions of the brain associated with these skills. Both groups demonstrated age-associated tissue thinning in the same brain regions, especially in the ventral striatum, a region vital for executive functions. However, diabetics demonstrated a greater degree of atrophy. Type 2 diabetics demonstrated more tissue shrinkage, akin to a 26% acceleration in normal aging of the human brain.
According to Lilianne Mujica-Parodi, senior researcher and professor at Stony Brook University School of Medicine in New York, type 2 diabetics have more atrophy in the same brain areas as non-diabetic individuals of their age; however, the aging happens much faster in type 2 diabetes.
The human brain is a huge consumer of glucose, and if the cells of the brain (neurons) fail to use the insulin hormone, the situation could be worrisome. “It’s like losing 10 years. If you starve a neuron, it’s going to undergo atrophy” said Mujica-Parodi. She further explained that it is starvation of the neurons of the brain, rather than vascular damage, that mainly drives the increased rate of brain aging in type 2 diabetes.
Michal Beeri, Professor of Psychiatry at Mount Sinai’s Icahn School of Medicine, New York City (NYC) who studies the relationship between diabetes and mental performance but was not involved in the research, said, “The findings do suggest that people with diabetes are showing accelerated aging in the brain.” Irrespective of the reasons underlying accelerated brain aging in individuals with type 2 diabetes, both Mujica-Parodi and Michal Beeri stressed the connection between the human brain and the rest of the body.
In agreement with Mujica-Parodi, Beeri said “There’s no reason to think that your diabetes stops at your neck. I’m surprised that when doctors talk to their patients with diabetes, they are often not bringing up brain health.” If type 2 diabetes contributes to faster cognitive decline, would treating diabetes help? In response to which Beeri said, “In theory, good glucose control should reduce the risk.”
Studies have linked the use of diabetes medications, like metformin, a to lesser risk of mental decline. But, Beeri states that those studies do not prove the medications, themselves, deserve the credit. However, in the present study, the use of metformin was not significantly linked to protecting the brain; the finding is inconclusive, according to Mujica-Parodi.
Beeri pointed out that good glucose control is essential for several reasons, and is something diabetics should be doing anyway. Prevention is ideal and although some risk factors for type 2 diabetes such as older age and family history cannot be changed, a healthy and balanced diet, regular exercise, and losing excess body weight can be beneficial.