Type 2 diabetes is associated with brain atrophy

Type 2 diabetes subjects the brain to insult by high levels of both insulin and glucose. A study just published in the journal Diabetes Care shows that brain atrophy resembling Alzheimer's disease exceeds cerebrovascular disease (brain ischemia and stroke) in type 2 diabetes. The authors determined to resolve whether cognitive dysfunction in T2DM was linked more to brain atrophy or vascular disease in the brain:

"Type 2 diabetes (T2DM) is associated with brain atrophy and cerebrovascular disease. We aimed to define the regional distribution of brain atrophy in T2DM and to examine whether atrophy or cerebrovascular lesions are feasible links between T2DM and cognitive function."

They examined 350 type 2 diabetes subjects with MRI and cognitive tests (and 363 controls without T2DM). With the MRI they mapped the regional distribution of brain atrophy. They also measured cerebrovascular lesions (infarcts, microbleeds, and white matter hyperintensity [WMH] volume) and atrophy (gray matter, white matter, and hippocampal volumes), and looked for links with loss of cognitive function.

"T2DM was associated with more cerebral infarcts and lower total gray, white, and hippocampal volumes but not with microbleeds or WMH [white matter hyperintensity]. T2DM-related gray matter loss was distributed mainly in medial temporal, anterior cingulate, and medial frontal lobes, and white matter loss was distributed in frontal and temporal regions. T2DM was associated with poorer visuospatial construction, planning, visual memory, and speed independent of age, sex, education, and vascular risk factors. The strength of these associations was attenuated by almost one-half when adjusted for hippocampal and total gray volumes but was unchanged by adjustment for cerebrovascular lesions or white matter volume."

In other words, as the authors were quoted in Medscape Family Medicine:

"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."

Additionally as noted in Medscape Family Medicine...

"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]."

Clinical note: Brain atrophy doesn't occur overnight. Practitioners should bear in mind that early elevations of HgbA1c and other markers of insulin resistance are a risk factor for cognitive dysfunction associated with brain atrophy. Biological functions regulated by brain arousal and inhibition are also vulnerable. The authors conclude:

"Cortical atrophy in T2DM resembles patterns seen in preclinical Alzheimer disease. Neurodegeneration rather than cerebrovascular lesions may play a key role in T2DM-related cognitive impairment."