Chronic pain is associated with brain volume loss in older adults: preliminary evidence.

Objectives: The primary aim of this pilot investigation was to identify structural brain differences in older adults with chronic low back pain (CLBP) as compared with pain-free individuals.

Design: Cross-sectional, case-control.

Participants: Sixteen cognitively intact older adults, eight with CLBP and eight pain-free; excluded if with psychiatric or neurological disorders, substance abuse, opioid use, diabetes mellitus, and/or hypertension.

Methods: Brain magnetic resonance imaging (MRI) and tests of neuropsychological performance (digit span, digit symbol substitution, letter-number sequencing, trail making) were administered to all participants. Gray matter (GM), white matter (WM), cerebrospinal fluid, and corpus callosum (CC) volumes were measured as a percentage of total supratentorial intracranial volume. Voxel-based morphometry analysis of GM and WM assessed regional differences.

Results: Between-groups analysis revealed a non-significant trend toward decreased middle CC volume in the CLBP group (1.43E-03 +/- 2.67E-04, 1.63E-03 +/- 2.00E-04: P = 0.09). Regional analysis in the CLBP group demonstrated significantly decreased GM volume (P < 0.001) in the posterior parietal cortex and middle cingulate WM volume (P < 0.001) of the left hemisphere. CLBP participants performed significantly worse on digit span forward (P = 0.03).

Conclusions: Older adults with CLBP have structural brain changes in the middle CC, middle cingulate WM, and the GM of the posterior parietal cortex as well as impaired attention and mental flexibility. Additional investigation is needed to corroborate and extend these findings and more clearly elucidate their relationship to physical function and the risk of disability.