Can diabetes trigger Alzheimer's disease?

Summarized by Robert W. Griffith, MD
March 24, 2000 (Reviewed: November 11, 2002)

It is well known that people with diabetes are likely to have problems with their circulation. Moreover, some studies have shown that a form of dementia, called vascular dementia, is commoner in people with diabetes. There is therefore considerable interest as to whether Alzheimer's disease is also commoner in people with diabetes. This was examined in the article summarized, which analyzed information from a large population of persons living in a suburb of the Dutch city Rotterdam.

All persons 55 or over in this suburb were invited to take part. About 8,000 accepted, and, after extensive testing, over 6,500 of them who were free of Alzheimer's disease or any similar dementia were enrolled. Their average age was 69, and 59% of them were women.

Diabetes was diagnosed based on whether the participants took antidiabetic medication, or if their blood glucose level was raised (above 200 mg/dL, or 11 mmol/L) after a glucose drink. They answered questions concerning their lifestyle and a range of activities that might be relevant - smoking, use of alcohol, level of education, other diseases, and so on.

After an average of just over two years the participants were examined again for any evidence of dementia. At that time, 126 had developed dementia, 70% of them having Alzheimer's disease, and 14% so-called vascular dementia.

Having diabetes almost doubled the risk of having dementia (the risk was 1.9 times greater). The risk of diabetics getting Alzheimer's disease was also nearly double. And in diabetics taking insulin, the risk was over 4 times that in non-diabetics. Even after adjusting for possible effects of sex, age, educational level and the other factors measured, the findings were the same.

This large study showed clearly that diabetes was associated with an increased risk of developing dementia - either Alzheimer's disease or other types of dementia. Although it was anticipated that diabetes would increase the risk of vascular dementias, the results for Alzheimer's disease were unexpected. However, the study was large, and carefully conducted, so that reliance can be placed in the findings.

One must conclude from these results that diabetes is a risk factor for the development of dementias, including Alzheimer's disease. This makes it important to treat diabetes vigorously, so that blood sugar levels are kept under quite tight control; this should, one hopes, make the occurrence of dementia less likely.

Source

• Diabetes mellitus and the risk of dementia A. Ott, RP. Stolk, F. Van Harskamp, The Rotterdam Study. Neurology, 1999, vol. 53, pp. 1937--1942

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