Gray-Matter Atrophy May Drive Cognitive Decline in Diabetes

Marlene Busko

August 22, 2013

Older individuals with type 2 diabetes are more likely to have brain atrophy than cerebrovascular lesions — and the pattern resembles that seen in preclinical Alzheimer's disease — according to a new study that was published online August 12 in Diabetes Care.

Chris Moran, MB, from Monash University, Melbourne, Australia, and colleagues used MRI scans and measures of cognitive performance to examine differences between people with and without type 2 diabetes.

Type 2 diabetes "was clearly associated with poorer function in visual construction, planning, visual memory, and cognitive speed," they report. "The findings suggest that the predominant pathway linking [type 2 diabetes] and cognition (at least early in the course of disease) is brain atrophy," they add.

According to Dr. Moran and colleagues, "this study is the first to demonstrate that brain atrophy rather than cerebrovascular lesions may substantially mediate the relationship between [type 2 diabetes] and cognitive impairment."

Brain Atrophy in Diabetes

Type 2 diabetes is linked with a greater risk of developing cognitive impairment, dementia, or Alzheimer's disease, but few studies have clarified the pattern of brain atrophy in diabetes, the researchers write.

They performed a cross-sectional study in 350 men and women age 55 years and older who lived in Southern Tasmania and participated in the Cognition and Diabetes in Older Tasmanians (CDOT) study between 2008 and 2010.

The comparison group consisted of 363 men and women aged 60 years and older who lived in the same region, participated in the Tasmanian Study of Cognition and Gait (TASCOG), and did not have diabetes.

The participants with diabetes had a mean age of 67.8 years, and 40% were women, whereas those without diabetes had a mean age of 72.1, and 46% were women. All had MRI brain scans and performed a series of cognitive tests. Voxel-based morphometry was used to study the distribution of brain atrophy.

"In addition to the previously established association with hippocampal atrophy, [type 2 diabetes] was associated with temporal, frontal, and limbic gray-matter atrophy and to a lesser extent with frontal and temporal white-matter atrophy," Dr. Moran and colleagues report.

Type 2 diabetes was also linked with poorer performance in certain cognitive tests, and the strength of these associations dropped by almost half when adjusted for hippocampal and total gray-matter volumes but was unchanged when adjusted for cerebrovascular lesions or white-matter volume.

Patients with type 2 diabetes were more likely to have gray-matter atrophy in several bilateral regions of the cortices, especially in the left hemisphere. This pattern was remarkably similar to the distribution of cortical atrophy that has been described in early Alzheimer's disease, the investigators note.

"Gray-matter atrophy associated with [type 2 diabetes] is widely and bilaterally distributed in hippocampi, temporal, frontal, and cingulate cortices and subcortical nuclei," they summarize. "It appears to be the primary driver of cognitive dysfunction in people with [type 2 diabetes]."

Dr. Moran is a recipient of an Alzheimer's Australia Dementia Research Foundation Scholarship. Disclosures for the coauthors are listed in the article.

Diabetes Care. Published online August 12, 2013. Abstract

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