Diabetes Is a Risk Factor for Alzheimer's Disease

NEW YORK (Reuters Health) May 17 - Findings from a new study indicate that patients with diabetes mellitus are 65% more likely to develop Alzheimer's disease than people without diabetes. The results support several recent reports that have linked the two diseases.

In contrast, in some earlier studies, researchers were unable to show an association.

According to lead author Dr. Zoe Arvanitakis, from Rush University Medical Center in Chicago, what sets the current study apart from its predecessors is its longitudinal design and the rigorous method of assessing cognitive function.

"Surprisingly few longitudinal studies have examined the relationship of diabetes to Alzheimer's disease," Dr. Arvanitakis told Reuters Health. Also, unlike previous studies, "we used a detailed battery of neuropsychological tests to derive five cognitive abilities" that were used to evaluate changes in cognitive function, she added.

As reported in the Archives of Neurology for May, the researchers assessed the outcomes of 824 older Catholic nuns, priests, and brothers who participated in the Religious Orders Study. At baseline, all of the subjects were Alzheimer's-free and 127 had diabetes mellitus.

During an average follow-up period of 5.5 years, 151 subjects developed Alzheimer's disease, the authors note. As noted, the presence of diabetes raised the risk of Alzheimer's disease by 65%.

In terms of cognitive abilities, only perceptual speed demonstrated an accelerated rate of functional decline associated with diabetes (p = 0.02). This rate was increased by about 44% in diabetics compared with nondiabetics. "This was an interesting finding-it helps us understand some subtle issues that may help us shed light on the mechanisms" linking diabetes with Alzheimer's disease, Dr. Arvanitakis said.

Further answers may come with additional follow-up of the present cohort, she said. In addition, "all participants in the Religious Orders Study have agreed to brain donation at the time of death, which will allow us to look closer at the pathologic basis for the association."

Arch Neurol 2004;61:661-666.