Steeper Slope of Age-Related Changes in White Matter Microstructure and Processing Speed in Bipolar Disorder.
OBJECTIVE
Bipolar disorder (BD) is associated with compromised white matter (WM) integrity and deficits in processing speed (PS). Few studies, however, have investigated age relationships with WM structure and cognition to understand possible changes in brain health over the lifespan. This investigation explored whether BD and healthy counterpart (HC) participants exhibited differential age-related associations with WM and cognition, which may be suggestive of accelerated brain and cognitive aging.


METHODS
Cross-sectional study.


METHODS
University of California San Diego and the Veterans Administration San Diego Healthcare System.


METHODS
33 euthymic BD and 38 HC participants.


METHODS
Diffusion tensor imaging was acquired as a measure of WM integrity, and tract-specific fractional anisotropy (FA) was extracted utilizing the Johns Hopkins University probability atlas. PS was assessed with the Number and Letter Sequencing conditions of the Delis-Kaplan Executive Function System Trail Making Test.


RESULTS
BD participants demonstrated slower PS compared with the HC group, but no group differences were found in FA across tracts. Multiple linear regressions revealed a significant group-by-age interaction for the right uncinate fasciculus, the left hippocampal portion of the cingulum, and for PS, such that older age was associated with lower FA values and slower PS in the BD group only. The relationship between age and PS did not significantly change after accounting for uncinate FA, suggesting that the observed age associations occur independently.


CONCLUSIONS
Results provide support for future study of the accelerated aging hypothesis by identifying markers of brain health that demonstrate a differential age association in BD.
Research Service, Veterans Affairs San Diego Healthcare System, San Diego, CA; Departments of Psychiatry, University of California, San Diego, CA; San Diego State University/University of California, San Diego Joint Doctoral Program in Clinical Psychology, San Diego, CA. Electronic address: sdev25@gmail.com.
Sheena I
SI
Dev
Mental Illness Research, Education, and Clinical Center, Veterans Affairs San Diego Healthcare System, San Diego, CA; Departments of Psychiatry, University of California, San Diego, CA.
Tanya T
TT
Nguyen
Departments of Psychiatry, University of California, San Diego, CA.
Benjamin S
BS
McKenna
Research Service, Veterans Affairs San Diego Healthcare System, San Diego, CA; Departments of Psychiatry, University of California, San Diego, CA.
Ashley N
AN
Sutherland
Department of Radiology, University of California, San Diego, CA.
Hauke
H
Bartsch
Department of Radiology, University of California, San Diego, CA.
Rebecca J
RJ
Theilmann
Research Service, Veterans Affairs San Diego Healthcare System, San Diego, CA; Departments of Psychiatry, University of California, San Diego, CA; San Diego State University/University of California, San Diego Joint Doctoral Program in Clinical Psychology, San Diego, CA.
Lisa T
LT
Eyler
D000328:Adult; D000368:Aged; D000375:Aging / Q000473:pathology* / Q000502:physiology*; D016880:Anisotropy; D001714:Bipolar Disorder / Q000473:pathology* / Q000503:physiopathology*; D001921:Brain / Q000473:pathology / Q000503:physiopathology; D016022:Case-Control Studies; D003071:Cognition / Q000502:physiology*; D056324:Diffusion Tensor Imaging; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D014145:Trail Making Test; D066127:White Matter / Q000473:pathology*
Bipolar; DTI; aging; processing speed; white matter