A recent Australian study finds that older patients with diabetes may struggle more with verbal memory and fluency than those without diabetes.
Scientists have known a link between cognitive decline and diabetes exists in older patients, but according to Dr. Michele L. Callisaya, one of the study authors, “it is still not entirely clear why people with T2D are at greater risk of dementia.”
However, she tells dLife there are likely to be multiple mechanisms at play:
Glucose is the primary source of energy for the brain, but both high and low blood sugars are likely to adversely affect the brain’s ability to function.
“High blood sugar levels, as well as hypertension and chronic low-grade neuro-inflammation, may result in damage to the blood vessels in the brain or frequent episodes of blood sugar levels dropping too low may also increase the risk of cognitive impairment,” she tells dLife.
Keeping blood sugars within a healthy range is important to prevent a number of diabetes related complications.
However, Callisaya points out that results of a large randomized controlled study (the Memory in Diabetes sub-study of the Action to Control Cardiovascular Risk in Diabetes), did not find that intensive glucose control (target A1c <6.0%) was more beneficial than that standard control (target A1c 7.0-7.9%) for cognitive function.
The aim of Callisaya and her colleagues’ current study was to examine whether type 2 diabetes is associated with greater brain atrophy and cognitive decline and whether brain atrophy intervenes between type 2 diabetes and cognitive decline in any way.
Previous research has shown that T2D is associated with cognitive decline and can double the risk of dementia. “We set out to determine whether brain atrophy might explain this greater risk in people with T2D,” she says.
The researchers found that although memory and executive function declined at a greater rate in people with T2D, this was not explained by the decline in brain volume.
“The findings of an accelerated cognitive decline in people with T2D are important as they may contribute to difficulties in everyday activities and health behaviors —such as remembering to take medication,” she states.
Interestingly, brain volume was lower in people with T2D at the start of the study suggesting that the effect of T2D on the brain volume begin earlier in life – for example, during midlife.
How was the Study Conducted?
Participants who did not have dementia ranging from 55–90 years old were recruited from the Cognition and Diabetes in Older Tasmanians study.
They underwent brain MRI and neuropsychological measures, which tested for global function and seven cognitive domains.
The assessments were done during three different time intervals over five years.
The researchers used mixed models to examine associations of type 2 diabetes with cognitive and MRI measures. A test of mediation was used to determine whether brain atrophy explained associations between type 2 diabetes and cognitive decline.
What did Researchers Find?
Out of a total of 705 participants, 348 had diabetes, with a mean age of 68, and 357 participants did not diabetes, with a mean age of 72.5 years.
Adjusting for age, sex, education and vascular risk factors, the researchers found that in people with diabetes, verbal fluency declined slightly over the course of the study, while it improved slightly in participants without diabetes.
The researchers indicate people with diabetes already had more brain atrophy at the start of the study, however, there was no difference between those with and without diabetes in the rate of brain atrophy during the study.
They also state that atrophy doesn’t clearly explain the link between diabetes and cognitive decline.
The researchers conclude that in the older community, type 2 diabetes is associated with a decline in verbal memory and fluency over approximately 5 years.
As far as if there is anything that older patients can do to prevent the decline of verbal memory and fluency, Callisaya says “what is good for the heart is good for the brain,” and this should include physical activity, a healthy diet, healthy weight range, and checking blood pressure and cholesterol, and keeping blood sugars in a healthy range.
The message for patients, Callisaya emphasizes, is don’t wait until an older age. She says mentally challenging the brain and enjoying social activities, is also an important part of prevention.
“Recommendations for good brain health include physical activity, following a healthy diet, maintaining a healthy weight, checking blood pressure and cholesterol, mentally challenging the brain and enjoying social activities.”
The research has been published in Diabetologia.
Callisaya, M., Beare, R., Moran, C., Phan, T., Wang, W., Srikanth, V., Type 2 diabetes mellitus, brain atrophy and cognitive decline in older people: a longitudinal study. (2018, Dec. 13). Diabetologia. Retrieved: https://link.springer.com/article/10.1007%2Fs00125-018-4778-9.