Frontal-striatal tract integrity and depression in older adults with and without multiple sclerosis.

OBJECTIVE: Lower white matter integrity of frontal-subcortical circuitry has been associated with late-life depression in normally aging older adults and with the presence of multiple sclerosis (MS). Frontal-striatal white matter tracts involved in executive, cognitive, emotion, and motor function may underlie depression in older adults with MS. The present study examined the association between depression score and frontal-striatal white matter integrity in older adults with MS and controls.

METHODS: Older adults with MS (OAMS) (n = 67, mean age = 64.55 ± 3.89) and controls (n = 74, mean age = 69.04 ± 6.32) underwent brain MRI, cognitive assessment, psychological, and motoric testing. Depression was assessed through the 30-item Geriatric Depression Scale. Fractional anisotropy (FA) was extracted from two bilateral tracts: dorsolateral prefrontal cortex to putamen nucleus (DLPFC-pn) and dorsolateral prefrontal cortex to caudate nucleus (DLPFC-cn).

RESULTS: OAMS reported significantly worse (i.e., higher) depression symptoms (β = .357, p < .001) compared to healthy controls. Adjusted moderation analyses revealed, via group by FA interactions, significantly stronger associations between FA of the left DLPFC-pn tract and total depression (B =  - 61.70, p = .011) among OAMS compared to controls. Conditional effects revealed that lower FA of the left DLPFC-pn was significantly associated with worse (i.e., higher) depression symptoms (b =  - 38.0, p = .028) only among OAMS. The other three tracts were not significant in moderation models.

CONCLUSIONS: We provided first evidence that lower white matter integrity of the left DLPFC-pn tract was related to worse depression in older adults with MS.