New research shows that type 2 diabetes is associated with a decline in verbal memory and fluency in older people.
However, contrary to previous studies, the decrease in brain volume often found in older people with type 2 diabetes was not found to be directly associated with cognitive decline during the five-year time period which was measured for the research.
Previous research has also shown that type 2 diabetes can double the risk of dementia in older people.
In this new study, Dr Michele Callisaya, from the University of Tasmania and Monash University, aimed to discover whether type 2 diabetes is associated with greater brain atrophy and cognitive decline, and whether the two are linked.
It is the first study to compare decline in both cognition and brain atrophy between people with and without type 2 diabetes together in the same study.
The trial recruited 705 people aged 55 to 90 years from the Cognition and Diabetes in Older Tasmanians (CDOT) study. There were 348 people with type 2 diabetes (mean age 68 years) and 357 without (mean age 72 years) who underwent brain MRI (lateral ventricular and total brain volume – measures of brain atrophy) and neuropsychological measures (global function and seven cognitive domains) at three time points over a mean follow-up period of 4.6 years.
The results were adjusted for age, sex, education and vascular risk factors including past or current smoking, heart attack, stroke, high blood pressure, high cholesterol and body mass index.
The authors reported there were significant associations found between type 2 diabetes and greater decline in both verbal memory and verbal fluency.
Although people with diabetes had evidence of greater brain atrophy at the start of the study, there was no difference in the rate of brain atrophy between those with and without diabetes over the course in this study.
There was also no evidence in the study that the rate of brain atrophy had a direct impact on the diabetes-cognition relationship.
In people without type 2 diabetes, verbal fluency slightly increased on average each year, whereas it declined in those with type 2 diabetes.
“Such accelerated cognitive decline may contribute to executive difficulties in everyday activities and health behaviours – such as medication compliance – which in turn may poorly influence future vascular health and cognitive decline, and possibly an earlier onset of dementia in those with type 2 diabetes,” the authors said in their report.
“In older community-dwelling people, type 2 diabetes is associated with a decline in verbal memory and fluency over approximately five years, but the effect of diabetes on brain atrophy may begin earlier, for example in midlife, given the evidence of greater brain atrophy in people with type 2 diabetes at the start of the study.
“If this is the case, both pharmacological and lifestyle interventions to prevent brain atrophy in people with type 2 diabetes may need to commence before older age.”
What do you think? Do you have diabetes? How is your memory holding up?