Type 2 diabetes linked to cognitive decline in older adults

Type 2 diabetes can accelerate both a loss in cognitive function and impairment of cerebral vasoregulation in older adults, according to research in Neurology.

In a prospective study of older adults with and without type 2 diabetes, researchers found that global and regional cerebral vasoreactivity decreased by more than 50% during a 2-year period in the type 2 diabetes arm, and that vasoreactivity and vasodilation were positively associated with performance on daily living activities and executive function tests.

“Type 2 diabetes alters the regulation of blood flow in the brain, accelerates brain aging, and impairs mental functions and memory,” Vera Novak, MD, PhD, of Harvard Medical School and Beth Israel Deaconess Medical Center in Boston, told Endocrine Today. “Older adults with type 2 diabetes are at greater risk of profound impairment of mental function at younger age.”

Vera Novak

Vera Novak

Novak and colleagues analyzed data from 65 adults aged 50 to 85 years (mean age, 66 years; 33 women) enrolled in a 2-year study. Within the cohort, 35 participants had type 2 diabetes for more than 5 years. Researchers used MRI to measure global and regional cerebral perfusion and vasoreactivity, and they conducted verbal learning, memory function, visual-spatial ability and visual memory function tests at baseline and again at completion of the study. Researchers also measured serum glucose, HbA1c and inflammation markers, including soluble intercellular adhesion molecule, soluble vascular adhesion molecule, cortisol, interleukin-6 and tumor necrosis factor-alpha. Researchers used least-squares models to measure associations between serum inflammatory markers, regional cerebral vasoreactivity and cognitive function.

After 2 years of follow-up, researchers found that the type 2 diabetes arm had lower global gray matter volume and lower composite learning and memory compared with controls, as well as lower global and regional cerebral vasoreactivity and a decline in multiple cognitive tasks when compared with baseline (P < .0001-.012). In the control group, vasoreactivity declined in the insular cortex only, according to researchers.

In the type 2 diabetes arm, higher serum soluble intercellular and vascular adhesion molecules, higher cortisol, and higher C-reactive protein levels at baseline were linked to greater decreases in cerebral vasoreactivity and vasodilation, independent of diabetes control and 24-hour blood pressure.

Researchers found participants with a higher HbA1c at baseline showed a greater decline on Mini-Mental State Examination (MMSE) scores, composite executive function T-scores and overall composite T-scores independent of age, sex, education and baseline MMSE scores.

“Our results suggest that hyperglycemia imposes a chronic negative effect on cognitive functions in the [type 2 diabetes] population,” the researchers wrote. “These findings are consistent with previous studies that demonstrated that higher HbA1c levels are associated with faster cognitive decline.”

A study with a larger sample size and follow-up is needed to establish the time sequence of the relationship between blood flow and regulation and changes in cognition skills in older adults with type 2 diabetes, according to researchers.

“More studies are needed to find therapies protecting the brain in type 2 diabetes,” Novak said. “We are currently starting a research study that will evaluate whether intranasal insulin that is delivered directly to the brain can prevent cognitive decline in older adults with type 2 diabetes.” by Regina Schaffer

Disclosure: The researchers report no relevant financial disclosures.

For more information:

Vera Novak, MD
PhD, can be reached at the department of neurology, stroke division, at Beth Israel Deaconess Medical Center, 185 Pilgrim Road Palmer 127, Boston, MA 02215; email: vnovak@bidmc.harvard.edu

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