A study published today in eLife shows that the normal aging process is accelerated by around 26% in adults with type 2 diabetes compared to those without the disease.

The authors looked at how normal aging affects the brain and how type 2 diabetes affects the brain. They found that neurodegeneration in type 2 diabetes follows the same pattern as normal aging, but it happens faster. As a result, even normal brain aging may be associated with changes in insulin’s ability to regulate blood glucose levels in the brain.

The findings also show that by the time type 2 diabetes is properly diagnosed, severe anatomical damage to the brain may have occurred. Therefore, there is an urgent need for sensitive methods that can detect alterations that are related to diabetes in the brain.

Although there is considerable evidence that type 2 diabetes is linked to cognitive impairment, only a small percentage of patients receive a full cognitive assessment as part of their clinical care. It can be difficult to tell the difference between typical middle-age brain aging and brain aging induced or exacerbated by diabetes. So far, no studies have directly compared how the brains of healthy people change over the course of their lives with how the brains of people with diabetes change at the same age.

“Routine clinical assessments for diagnosing diabetes typically focus on blood glucose, insulin levels and body mass percentage,” explains Botond Antal. “However, the neurological effects of type 2 diabetes may reveal themselves many years before they can be detected by standard measures, so by the time type 2 diabetes is diagnosed by conventional tests, patients may have already sustained irreversible brain damage.”

The team used the largest available brain structure and function dataset spanning the human lifespan: UK Biobank data from 20,000 adults aged 50 to 80 years old to identify the impact of diabetes on the brain over and above normal aging. This dataset contains data from both healthy people and people who have been diagnosed with type 2 diabetes, and it includes brain scans and brain function assessments. They analyzed this to figure out which brain and cognitive changes are unique to diabetes rather than aging, and then backed up their findings using a meta-analysis of over 100 other studies.

Findings from their study indicate the effects of aging on executive skills, such as working memory, as well as type 2 diabetes on the brain’s processing speed. When compared to adults of the same age without diabetes, people with diabetes experienced a further 13.1 percent decline in executive function beyond age-related effects, and their processing speed reduced by 6.7 percent. Their meta-analysis of other studies verified this finding: people with type 2 diabetes had consistently and significantly worse cognitive function than healthy people of similar age and education.

MRI images were also used to assess brain anatomy and activity in patients with and without diabetes. They discovered a loss in grey brain matter with age, mainly in an area known as the ventral striatum, which is important for executive functions in the brain. When compared to normal aging, those with diabetes exhibited even more dramatic losses in gray matter, with a further 6.2 percent decline in grey matter in the ventral striatum, as well as loss of grey matter in other regions.

The findings imply that the patterns of type 2 diabetes-related neurodegeneration closely resemble those of normal aging, but that neurodegeneration occurs at a faster rate. Furthermore, the impairments on brain function were more severe as the duration of diabetes increased. Diabetic progression has been associated with a 26 percent faster rate of brain aging.

“Our findings suggest that type 2 diabetes and its progression may be associated with accelerated brain aging, potentially due to compromised energy availability causing significant changes to brain structure and function,” asserts senior author Lilianne Mujica-Parodi. “By the time diabetes is formally diagnosed, this damage may already have occurred. But brain imaging could provide a clinically valuable metric for identifying and monitoring these neurocognitive effects associated with diabetes. Our results underscore the need for research into brain-based biomarkers for type 2 diabetes and treatment strategies that specifically target its neurocognitive effects.”

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