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Type 2 Diabetes Slows Mental Processing Speed

Nov 25, 2008

New research shows that among the cognitive abilities that are affected by type 2 diabetes, processing speed appears to be the most severely impaired, particularly in patients with undiagnosed disease.

Findings from several studies have linked type 2 diabetes with cognitive dysfunction, Dr. Jane S. Saczynski, from the University of Massachusetts Medical School, Worcester, and colleagues state. However, it was unclear which cognitive domains were most affected and how undiagnosed diabetes and abnormal fasting glucose levels influenced cognitive performance.


To investigate, Dr. Saczynski’s team analyzed data from 1917 non-demented men and women enrolled in the Age, Gene/Environment Susceptibility — Reykjavik Study, a population-based investigation that ran from 2002 to 2006. The study participants were born in Reykjavik between 1907 and 1935, and the average age was 76 years old.

The subjects included 955 who were normoglycemic, 744 with impaired fasting glucose, 163 with diagnosed diabetes, and 55 with undiagnosed diabetes. A neuropsychological battery was used to construct composites of memory, processing speed, and executive function.

Compared with normoglycemic subjects, patients with diagnosed diabetes had significantly slower processing speed (p < 0.05). Memory performance and executive function were comparable in the two groups, except for those who had diabetes for 15 years or longer, for whom significantly poorer executive function was also observed.

For those with undiagnosed diabetes, both processing speed (p < 0.001) and memory performance (p < 0.05) were significantly worse relative to their normoglycemic peers.

For patients with impaired fasting glucose, cognitive performance in all three areas was on par with that seen in normoglycemic subjects.

“Given the increasing prevalence of type 2 diabetes in older adults and the complexity of disease management in these high-risk individuals, future treatment protocols should be developed with the cognitive status of patients with type 2 diabetes in mind,” the research team concludes.

Am J Epidemiol Nov. 15 2008;168:1132-1139.


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