Abstract
Despite the high risk of dementia in older adults with type 2 diabetes, the neuroanatomical correlates of cognitive dysfunction that are particularly affected by diabetes are not well characterized. This study is aimed to examine the structural brain alterations in dysglycemic older adults. Using voxel-based morphometric and tract-based spatial statistics, we examined changes in gray matter volume, white matter volume, and microstructural integrity in older adults with prediabetes and diabetes. We also assessed the correlation of these structural changes with diabetes biomarkers and cognitive performance. A total of 74 non-demented older adults (normal, n = 14; prediabetes, n = 37; and diabetes, n = 23) participated in this study and underwent structural and diffusion magnetic resonance imaging (MRI) scans and neuropsychological tests. Subjects with diabetes showed reduced volume of cerebellar gray matter and frontal white matter and diffuse white matter dysintegrity, while those with prediabetes only showed reduced volume of insular gray matter. Atrophic changes in the cerebellum and frontal lobe and frontal white matter dysintegrity were correlated with chronic hyperglycemia and insulin resistance and worse performance in verbal memory recognition and executive function tests. Our findings suggest that chronic hyperglycemia and insulin resistance may alter brain structures forming the fronto-cerebellar network, which may cause cognitive dysfunction in older adults.
Highlights
The prevalence rates of both type 2 diabetes and dementia increase with age, and older adults are often concomitantly affected by both diseases [1]
The prediabetes group had smaller gray matter volume in the left anterior insula and left frontal lobe than the normal glucose tolerance (NL) group; there was no significant difference between prediabetes group and NL group with respect to white matter volume
With respect to white matter microstructural alterations, the diabetes group showed widespread reduction in fractional anisotropy (FA) and increase in mean diffusivity (MD) compared to the NL group (Figure 2)
Summary
The prevalence rates of both type 2 diabetes and dementia increase with age, and older adults are often concomitantly affected by both diseases [1]. Previous studies have found that type 2 diabetes increases the risk of cognitive decline and incident dementia [2,3,4]. Many researchers have reported alterations of brain structures in diabetes; there are several unresolved questions. It remains unclear whether volume changes in specific brain areas are associated with diabetes. The lack of voxel-based morphometry (VBM) studies in this field has limited the identification of unexpected regions related to the pathophysiology of diabetes. It has not been identified whether alteration of brain atrophy in specific regions is correlated with cognitive decline in dysglycemic older adults. Use of diffusion tensor imaging (DTI) or VBM analysis may help overcome the limitations of previous studies; these modalities have not been applied to participants with prediabetes
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