Diabetes Care, Vol 23, Issue 10 1486-1493, Copyright © 2000 by American Diabetes Association
Circumscribed cognitive dysfunction in middle-aged adults with type 2 diabetes
CM Ryan and MO Geckle
Department of Psychiatry, University of Pittsburgh School of Medicine, Pennsylvania, USA. ryancm@msx.upmc.edu
OBJECTIVE: To examine the extent to which type 2 diabetes is associated
with poorer performance on measures of learning, memory, psychomotor speed,
and problem-solving in middle-aged adults. RESEARCH DESIGN AND METHODS:
This cross-sectional study evaluated 50 adults (age range 34-65 years, mean
50.8) with type 2 diabetes and 50 demographically similar community control
subjects without diabetes. Each subject received a thorough physical
examination and a detailed neuropsychological assessment. Factor analysis
was used to assign specific tests to 1 of 4 cognitive domains (learning,
memory for stories, problem-solving, and psychomotor speed). Hierarchical
regression analysis was used to identify demographic and biomedical
variables associated with cognitive dysfunction. RESULTS: Learning, memory,
and problem-solving skills were unaffected by type 2 diabetes. In contrast,
psychomotor slowing was predicted by a diagnosis of diabetes (r2 change =
0.075, P < 0.002) with additional variance in psychomotor efficiency
explained independently by HbA1 (r2 = 0.064, P < 0.003) and vibratory
threshold (r2 = 0.112, P < 0.0001). The magnitude of psychomotor slowing
on specific tests ranged from 12% (Digit Vigilance) to 23% (Grooved
Pegboard). CONCLUSIONS: Middle-aged adults with type 2 diabetes manifest
psychomotor slowing that is associated with poorer metabolic control,
whereas learning, memory, and problem-solving skills appear to be largely
intact. The development of psychomotor slowing may be a manifestation of a
"central neuropathy" induced by chronic hyperglycemia.