Racial Differences in Gray Matter Integrity by Diffusion Tensor in Black and White Octogenarians.
OBJECTIVE
To quantify racial differences in brain structural characteristics in white and black octogenarians, and to examine whether these characteristics contribute to cognition.


METHODS
Cross-sectional study of 283 adults 79-89 years old (59.4% white;42.0% women) with data on gray matter integrity via diffusion tensor imaging (mean diffusivity), gray matter atrophy (GMA), white matter hyperintensities (WMH), literacy, smoking, drinking, income, hypertension and diabetes. Participants were recruited from an ongoing epidemiological study of older adults living in the community with a range of chronic conditions, physical and cognitive function. Standardized betas (sβ) of neuroimaging markers predicting Digit Symbol Substitution Test (DSST) and Modified Mini-Mental State Examination (3MS) scores were computed in multivariable regression models stratified by race.


RESULTS
Compared to whites, blacks had lower DSST (p=0.001) and lower 3MS (p=0.006), but also lower mean diffusivity (i.e. higher gray matter microstructural integrity, p=0.032), independent of gender, income, literacy, body mass index, diabetes and drinking habits. Racial differences were not significant for WMH (p=0.062) or GMA (p=0.4). Among blacks, mean diffusivity and WMH were associated with DSST (sβ=-.209, p=0.037 and -.211, p=.038, respectively) independent of each other and other covariates; among whites, mean diffusivity, but not WMH, was significantly associated with DSST and 3MS (sβ =-.277, p=.002 and -.250, p=0.029, respectively).


CONCLUSIONS
In this cohort of octogenarians living in the community, blacks appeared to have higher microstructural integrity of gray matter as compared to whites. This neuroimaging marker was related to higher cognition even in the presence of WMH and other cardiovascular conditions. If confirmed, these findings suggest microstructural gray matter integrity may be a target to improve cognition, especially among blacks who survive to very old age with a range of chronic cardiovascular conditions.
Ge
G
Liu
Ben
B
Allen
Oscar
O
Lopez
Howard
H
Aizenstein
Robert
R
Boudreau
Anne
A
Newman
Kristine
K
Yaffe
Stephen
S
Kritchevsky
Lenore
L
Launer
Suzanne
S
Satterfield
Eleanor
E
Simonsick
Center for Aging and Population Health, 130 N. Bellefield Avenue, Pittsburgh PA, 15213, USA. RosanoC@edc.pitt.edu.
Caterina
C
Rosano
D001741:Black or African American / Q000523:psychology; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000473:pathology* / Q000523:psychology; D001921:Brain / Q000473:pathology*; D003071:Cognition; D003430:Cross-Sectional Studies; D038524:Diffusion Magnetic Resonance Imaging; D056324:Diffusion Tensor Imaging; D005260:Female; D066128:Gray Matter / Q000473:pathology*; D006801:Humans; D008297:Male; D015999:Multivariate Analysis; D009483:Neuropsychological Tests; D010414:Pennsylvania / Q000453:epidemiology; D044465:White People / Q000523:psychology