A study involving older adults has found that diabetes was associated with higher levels of tau protein and greater brain atrophy.
The study involved 816 older adults (average age 74), of whom 397 had mild cognitive impairment, 191 had Alzheimer's disease, and 228 people had no cognitive problems. Fifteen percent (124) had diabetes.
Those with diabetes had greater levels of tau protein in the spinal and brain fluid regardless of cognitive status. Tau tangles are characteristic of Alzheimer's.
Those with diabetes also had cortical tissue that was an average of 0.03 millimeter less than those who didn't have diabetes, regardless of their cognitive status. This greater brain atrophy in the frontal and parietal cortices may be partly related to the increase in tau protein.
There was no link between diabetes and amyloid-beta, the other main pathological characteristic of Alzheimer's.
Previous research has indicated that people with type 2 diabetes have double the risk of developing dementia. Previous research has also found that those who had been diabetic for longer had a greater degree of brain atrophy
The findings support the idea that type 2 diabetes may have a negative effect on cognition independent of dementia, and that this effect may be driven by an increase in tau phosphorylation.
 Type 2 diabetes mellitus and biomarkers of neurodegeneration. Neurology [Internet]. 2015 :10.1212/WNL.0000000000001982. Available from: http://www.neurology.org/content/early/2015/09/02/WNL.0000000000001982