Summary

People with dementia show distinctive patterns of brain damage post-mortem, often deposits known as plaque. However, a new study shows that when treated diabetes and dementia occur together, a different pattern of brain lesions is found. This distinction might affect the way in which diabetes is managed in the context of dementia.

Introduction

Having diabetes increases the risk of developing dementia in later life. The reasons why are not clearly established. It may be that elevated blood glucose somehow promotes the development of plaques and tangles in the brain that are characteristic of Alzheimer's disease. It may also be that the vascular problems of diabetes increase the risk of multiple infarcts in the brain which are also a well-known sign of dementia. In a new study, the influence of diabetes upon the pattern of brain damage of dementia was uncovered.

What was done

Researchers at the University of Washington, Seattle, and colleagues elsewhere studied post-mortem brains of 196 individuals as part of the Adult Changes in Thought study, an community based study of dementia. They were divided into four groups: dementia and diabetes, dementia only, diabetes only, and neither disease.

What was found

In the 125 patients without dementia, the presence of diabetes did not affect any neurological or biochemical findings. But for those with dementia, there were clear differences in patterns of brain damage depending on whether the person had treated diabetes or not. Those with treated diabetes were more likely to have many tiny infarcts (areas of stroke damage) and more inflammation, while those with untreated diabetes or without diabetes had the more usual plaque deposits.

What this study means

The findings show a clear difference between those whose diabetes is treated and those whose disease is not. Further investigation is needed, but these differences in patterns of brain damage in dementia may help explain just why diabetes increases the risk of dementia. Both diseases are on the increase so any new understanding that can be used in prevention or treatment is to be welcomed.

Source

Sonnen JA, Larson EB et al Archives of Neurology advance online January 2009 66[3]:(doi:10.1001/archneurol.2008.579