How does type 2 diabetes mellitus (DM) accelerate cognitive decline?

Updated: Oct 23, 2019
  • Author: Romesh Khardori, MD, PhD, FACP; Chief Editor: George T Griffing, MD  more...
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In a cross-sectional study of 350 patients aged 55 years and older with type 2 diabetes and 363 control participants aged 60 years and older without diabetes, diabetic individuals were more likely to have brain atrophy than cerebrovascular lesions, with patterns resembling those of preclinical Alzheimer disease. [31, 32] Type 2 diabetes was associated with hippocampal atrophy; temporal, frontal, and limbic gray-matter atrophy; and, to a lesser extent, frontal and temporal white-matter atrophy.

Type 2 diabetes was also linked with poorer performance on certain cognitive tests. The strength of these associations dropped by almost 50% when adjusted for hippocampal and total gray-matter volumes but was unchanged when adjusted for cerebrovascular lesions or white-matter volume. [31, 32] 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, similar to the distribution of cortical atrophy described in early Alzheimer disease. [31]

In a 40-month study of 2977 middle-aged and older adults with long-standing type 2 diabetes, depression at baseline was associated with accelerated cognitive decline. [33, 34] The 531 subjects with scores of 10 or higher on the Patient Health Questionnaire Depression Scale at baseline had significantly lower scores on the Digit Symbol Substitution Test (DSST), the Rey Auditory Verbal Learning Test (RAVLT), and the modified Stroop test. Adjustment for other risk factors did not affect the association.

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