Multiple sclerosis (MS), an inflammatory autoimmune disease of the central nervous system, is characterized by damage to white matter via myelin degeneration with resulting sclerotic plaques and lesions. Upwards of 70% of people with MS show cognitive changes in multiple domains including verbal memory. Advances in disease-modifying therapies have increased the expected lifespan of people with MS, making aging with MS a critical emerging area of study. Memory declines during normal aging, yet the specific impact of MS on verbal memory in aging is inconclusive and understudied. To address this gap in knowledge, we examined whether MS was associated with verbal learning slope, total learning, delayed recall, and recognition performance in older adults. We further explored whether MS disease severity influenced these memory operations.

Participants included two cohorts: older adults with MS recruited from MS centers and patient registries, and healthy controls recruited from the community. A total of 164 adults age 60 and older without dementia were included in the current study, 79 in the MS group (mean age = 65.05 + 4.72; %female = 62) and 85 in the control group (mean age = 69.53 + 6.65; %female = 65.9). All participants were administered a neuropsychological battery including the Hopkins Verbal Learning Test-Revised (HVLT-R). The Patient Determined Disease Steps (PDDS), a patient-rated score of disability severity in MS comprised of eight steps related to walking ability, was used to operationalize MS severity. Using a median split, the PDDS was dichotomized into low (PDDS = 0-2) versus high (PDDS = 3-5) MS severity groups. Linear regression models were run to examine the effect of group (MS vs. control) and disease severity (PDDS) on four operations from the HVLT-R: learning slope, total learning, delayed recall, and recognition. Statistical analyses adjusted for age, years of education, and sex.

Linear regression models revealed that older adults with MS showed lower total learning compared to healthy controls (β = -.18, p = .03). Learning slope, delayed recall, and recognition did not differ by group (p > .05). Compared to healthy controls, older adults with high MS severity performed worse on total learning (β = -.21; p = .01) and delayed recall (β = -.18; p = .03). Group differences on learning slope and recognition were not significant (p > .05).

The presence of MS was associated with worse total learning. Moreover, high severity of MS was associated with worse total learning and delayed recall in older adults. These results delineate the influence of MS on specific memory operations and emphasize the potential utility of disease severity on cognitive performance in aging.