Aerobic Capacity Is Not Associated with Most Cognitive Domains in Patients with Multiple Sclerosis—A Cross-Sectional Investigation

Abstract

(1) Background: Cognitive impairment is highly prevalent in multiple sclerosis (MS). Staying physically fit may be associated with preservation of cognitive performance in persons with MS (pwMS); (2) Objective: To investigate the association between aerobic capacity and the cognitive domains of information processing, learning and memory, and verbal fluency as well as single and composite z-scores of the Brief Repeatable Battery of Neuropsychological tests (BRBNT) in pwMS; (3) Methods: All subjects first performed the BRBNT and then a maximal oxygen consumption (VO2-max) test on a bicycle ergometer as a measure of aerobic capacity. Simple and multiple (adjusting for age, sex, and education level) regression analyses were performed to evaluate the relationship between aerobic capacity and cognitive performance in different domains. Published international norms were used to compute z-scores for each individual and composite BRBNT score. Furthermore, cognitive impairment was defined as one or more z-scores ≤−1.5 standard deviation (SD) of healthy controls; (4) Results: Eighty-four subjects were included (44.9 ± 9 years, 16.3 ± 2 education years, Expanded Disability Status Scale (EDSS): 2.6 ± 1.4, MS-type (relapsing-remitting, primary progressive, or secondary progressive): 73/6/5, disease duration: 9.9 ± 7 years, VO2-max: 28.4 ± 7.0 mL O2/min/kg). No significant associations between aerobic capacity and cognitive performance in the individual BRBNT tests were found, except that a weak relationship was found between aerobic capacity and the composite processing speed z-score (R2 = 0.06, p = 0.02). The average global BRBNT z-score (−0.2 ± 0.66) was not associated with aerobic capacity. Comparison of the cognitively impaired group (34.5%) with the nonimpaired group (65.5%) showed lower aerobic capacity in the impaired group (25.9 ± 1 vs. 29.7 ± 1 mLO2/min/kg, p = 0.02); (5) Conclusions: Limited support was found for an association between performance in most cognitive domains and aerobic capacity in the present MS group with a third of patients showing signs of cognitive impairments.

Efficacy of high-intensity aerobic exercise on cognitive performance in people with multiple sclerosis: A randomized controlled trial

“…Previously, we reported absence of baseline correlations between cardiorespiratory fitness and all of the individual tests of the BRB-N in the same sample of pwMS, except for a weak relationship between cardiorespiratory fitness and the composite processing speed Z -score, which includes the SDMT and the PASAT. 24 Here, we present longitudinal cognitive performance data showing no effects of PAE in most tests, in both the total group and in the cognitively impaired group, when compared with waitlist controls. However, according to a clinically meaningful change of 4 points, 30 the cognitively impaired subgroup improved in the SDMT based on the between-group point estimate of +4.9 (–1.3 to 11.1), while the point estimate of the consistent long-term retrieval subtest of the SRT (+7.5 (–0.7 to 15.8)) similarly suggested improvements.…”

“…Further details on the cognitive performance test protocol in this trial and the seven different tests included in the BRB-N can be found elsewhere. 24…”

“…the composite processing speed Z -score includes the Symbol Digit Modalities Test (SDMT) and the 3-second version of the Paced Auditory Serial Addition Test (PASAT)) as previously described. 24 All longitudinal data for the total group and the cognitively impaired subgroup were analyzed using an intention-to-treat linear mixed effects model with time and group as the factors of interest. Age, sex, education level, MDI score, and MS type were a priori classified as important covariates and were therefore included in the model when analyzing cognitive performance outcomes.…”

Effect of High-Intensity Exercise on Multiple Sclerosis Function and Phosphorous Magnetic Resonance Spectroscopy Outcomes

“…The SDMT is measure of mental processing speed and not specific to the cognitive deficits such as learning and memory known to commonly occur in MS. Validated MS batteries of cognitive tests exist that might have greater sensitivity to demonstrate efficacy of the interventions (40). Yet newer evidence suggests that mental processing speed may be the cognitive domain best associated with aerobic capacity and best stand-alone cognitive task for MS (14,31)Other study limitations include lack of confounder assessments such as mood and sleep. Finally, the lack of randomized assignment to intervention cohorts tempers the robustness of the conclusions.…”

“…Cross-sectional studies in MS reveal positive associations between levels of physical activity and walking performance with fatigue, cognitive processing speed, brain volumes, and tract integrity (10)(11)(12). Longitudinal studies of aerobic exercise generally, although not invariably, demonstrate improvements in fitness and MS symptoms (3,13,14). The variations in results may be due to differences between studies in choice of exercise modality, duration, intensity, comparator group activity and outcome measures.…”