Diabetes, markers of brain pathology and cognitive function: the Age, Gene/Environment Susceptibility-Reykjavik Study.
OBJECTIVE
We investigated whether, and the extent to which, vascular and degenerative lesions in the brain mediate the association of diabetes with poor cognitive performance.


METHODS
This cross-sectional study included 4,206 participants (age > 65 years; 57.8% women) of the Age, Gene/Environment Susceptibility-Reykjavik Study. Data were collected through interview, clinical examination, psychological testing, and laboratory tests. The composite scores on memory, information-processing speed, and executive function were derived from a cognitive test battery. Markers of cerebral macrovascular (cortical infarcts), microvascular (subcortical infarcts, cerebral microbleeds, and higher white matter lesion volume), and neurodegenerative (lower gray matter, normal white matter, and total brain tissue volumes) processes were assessed on magnetic resonance images. Mediation models were employed to test the mediating effect of brain lesions on the association of diabetes with cognitive performance controlling for potential confounders.


RESULTS
There were 462 (11.0%) persons with diabetes. Diabetes was significantly associated with lower scores on processing speed and executive function, but not with memory function. Diabetes was significantly associated with all markers of brain pathology. All of these markers were significantly associated with lower scores on memory, processing speed, and executive function. Formal mediation tests suggested that markers of cerebrovascular and degenerative pathology significantly mediated the associations of diabetes with processing speed and executive function.


CONCLUSIONS
Diabetes is associated with poor performance on cognitive tests of information-processing speed and executive function. The association is largely mediated by markers of both neurodegeneration and cerebrovascular disease. Older people with diabetes should be monitored for cognitive problems and brain lesions.
Laboratory of Epidemiology and Population Sciences, National Institute on Aging, National Institutes of Health, Bethesda, MD; Aging Research Center, Department of Neurobiology, Care Sciences, and Society, Karolinska Institutet-Stockholm University, Stockholm, Sweden.
Chengxuan
C
Qiu
Sigurdur
S
Sigurdsson
Qian
Q
Zhang
Maria K
MK
Jonsdottir
Olafur
O
Kjartansson
Gudny
G
Eiriksdottir
Melissa E
ME
Garcia
Tamara B
TB
Harris
Mark A
MA
van Buchem
Vilmundur
V
Gudnason
Lenore J
LJ
Launer
D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000235:genetics* / Q000378:metabolism* / Q000473:pathology; D001921:Brain / Q000473:pathology; D001927:Brain Diseases / Q000453:epidemiology* / Q000235:genetics* / Q000473:pathology; D003071:Cognition / Q000502:physiology; D003072:Cognition Disorders / Q000453:epidemiology* / Q000235:genetics* / Q000473:pathology; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D003920:Diabetes Mellitus / Q000453:epidemiology* / Q000235:genetics* / Q000473:pathology; D004198:Disease Susceptibility / Q000378:metabolism / Q000473:pathology; D005260:Female; D006801:Humans; D007055:Iceland / Q000453:epidemiology; D008297:Male