Diabetes and dementia: Linked through insulin

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Systemic insulin resistance is the hallmark of type 2 (adult onset) diabetes. Studies done over the past several years have also found that a similar mechanism applies in the brain cells of Alzheimer s patients. Now, a study of over 1,000 people in Japan has found that diabetics may be at an increased risk for Alzheimer s disease (AD). The authors propose that the reason may have to do with brain neurons (nerve cells) of AD patients being insulin resistant.

The study, published in the journal Neurology, followed participants aged 60 and older over the course of 11 years, on average. Researchers used a glucose tolerance test to determine whether participants were diabetic or pre-diabetic. The researchers found that over one-fourth of those with diabetes developed dementia, compared to one-fifth of those with normal blood glucose levels findings that suggest that diabetes confers an increased risk of dementia.

In addition to the link between insulin resistance and dementia, the vascular diseases associated with diabetes disrupt the flow of oxygen to the brain which, researchers theorize, might also put one at risk for dementia. That is, a brain deprived of an adequate oxygen supply will result in declining cognitive function.

In response to the study results, doctors suggest that it may lead to a more rapid referral of diabetics to neurologists upon the first signs of any cognitive problems. It s also one more good reason for diabetic patients to make an effort to prevent the progression of vascular disease and to maintain proper blood sugar levels.

ACSH's Dr. Gilbert Ross says that, despite the relatively small difference in dementia risk, the study is still important. He notes the biological plausibility of the link between the two diseases: It s more research that suggests we do have control over some of the factors that contribute to dementia.