Diabetes mellitus is a known risk factor for several diseases including cardiovascular and cerebrovascular diseases such as heart attack and stroke. Diabetes causes elevated blood glucose levels which contribute to the formation of atherosclerotic plaque within the arteries. Atherosclerosis leads to the stenosis, or narrowing, of coronary arteries and cerebral arteries which can then progress to acute myocardial infarctions and cerebrovascular accidents. Researchers, lead by Dr. Yutaka Kiyohara, have provided evidence that diabetes mellitus is also associated with an increased risk of developing dementia. The results of their study were published online in the journal Neurology. The investigators evaluated the association between glucose tolerance status and the development of dementia using an oral glucose tolerance test. There were 1,017 dementia free individuals aged greater than 60 years enrolled in the Hisayama Study that participated in the current investigation. The researchers assessed glucose tolerance at the onset of the study and followed the participants for a 15 year period. The onset of diabetes, all cause dementia, Alzheimer’s disease, and vascular dementia was assessed. It was found that individuals with diabetes were twice as likely to develop Alzheimer’s disease as compared to the non-diabetic study participants. Diabetic study participants were found to be 74% more likely to develop all cause dementia. These associations remained even after adjustments were made for confounding factors such as age, sex, hypertension, body mass index, smoking, and total cholesterol level. In addition, the risks of developing all-cause dementia, Alzheimer’s disease, and vascular dementia were significantly increased with elevated 2-hour postload glucose levels. The diagnosis of dementia was confirmed by imaging studies or at autopsy in the study participants. The authors wrote, “Our findings emphasize the need to consider diabetes as a potential risk factor for all-cause dementia, [Alzheimer’s disease], and probably [vascular dementia]. The other main finding, that elevated 2-hour [postload glucose] levels are closely associated with increased risks of all-cause dementia and its subtypes, supports the view that postprandial glucose regulation is critical to prevent future dementia”. It is important to note that this is an association and does not prove a causal relationship. Further investigations will need to determine the exact mechanism for this association. In addition, future studies will need to determine whether controlling blood glucose levels, especially postprandially, can reduce the observed risk of developing dementia in diabetics.
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T. Ohara et al. “Glucose tolerance status and risk of dementia in the community: The Hisayama Study” Neurology September 20, 2011 77:1126-1134.