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Type 2 Diabetes and the Brain

A recent study adds to the list of health reasons to try to avoid type 2 diabetes if at all possible, such as making lifestyle changes (e.g. lose weight if overweight, improve diet,  exercise). Earlier studies found that the brain atrophies (decreases in volume) with type 2 diabetes, and that the presence of type 2 diabetes doubles the risk of dementia in older age. Yikes!

Similarly, Australian researchers in the recent study found that type 2 diabetes in older individuals is associated with decline in verbal memory and verbal fluency over a five year period, but the findings suggest that this may start in midlife.  This is because at the start of the study those with type 2 diabetes already showed signs of greater brain atrophy than those without type 2 diabetes. The type 2 diabetes group had "poorer cognitive function" at the start of the study, and then they continued to decline over the 5 year study time, but not at any greater rate than individuals without diabetes. In contrast to the decline in verbal fluency over the 5 year period in the diabetes group, the non-diabetes group actually showed an slight increase in verbal fluency each year.

Of the 705 persons in the study, the average age of the type 2 diabetes group was 68.2 years, while the non-diabetes group was 72.5 years - so can see that the diabetes group was generally younger. [Note that the brain shrinks a little as we age, and it's a normal part of aging, but you want to minimize it. The more "youthful" the brain, the better for cognitive functioning.

From Science Daily: In older people, type 2 diabetes is associated with a decline in brain function over 5 years, study shows

New research published in Diabetologia (the journal of the European Association for the Study of Diabetes [EASD]) shows that in older people living in the community, type 2 diabetes (T2D) is associated with a decline in verbal memory and fluency over 5 years

However, contrary to previous studies, the decrease in brain volume often found in older people with T2D was not found to be directly associated with cognitive decline during this time period. Yet compared with people without T2D, those with T2D had evidence of greater brain atrophy at the beginning of the study.

Previous research has shown that T2D can double the risk of dementia in older people. In this new study, Dr Michele Callisaya (University of Tasmania, Hobart, TAS, and Monash University, Melbourne, VIC, Australia) and colleagues aimed to discover whether type 2 diabetes is associated with greater brain atrophy and cognitive decline, and whether the two are linked.

The trial recruited 705 people aged 55-90 years from the Cognition and Diabetes in Older Tasmanians (CDOT) study. There were 348 people with T2D (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.

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 time course in this study. There was also no evidence in the study that the rate of brain atrophy directly impacted on the diabetes-cognition relationship.

In people without type 2 diabetes, verbal fluency slightly increased on average each year (0.004 SD/units per year), whereas it declined in those with type 2 diabetes (0.023 SD/units per year). The authors say: "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."

They conclude: "In older community-dwelling people, type 2 diabetes is associated with a decline in verbal memory and fluency over approximately 5 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 T2D at the start of the study. If this is the case, both pharmacological and lifestyle interventions to prevent brain atrophy in people with T2D may need to commence before older age."

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