Researchers said the effects can be seen even when levels of blood sugar, or glucose, are only moderately elevated, a finding that may help explain normal age-related cognitive decline, since glucose regulation worsens with age.
I wonder if this physiological link may also underlie the association between some mtDNA haplogroups and Alzheimer’s. In this case, the paper is able to analyze functional consequences of glucose levels because the authors were able to manipulate glucose levels in experimental animals. Remember this:
Previous observational studies have shown that physical activity reduces the risk of cognitive decline, and studies have also found that diabetes increases the risk of dementia. Earlier studies had also found a link between Type 2 diabetes and dysfunction in the dentate gyrus.
Here the causality is not necessarily clear. Maybe people who have healthy metabolic profiles are more likely to be active and less likely to exhibit cognitive declines. In that scenario, you wouldn’t necessarily benefit from changing your activity pattern.