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PHYSICAL FITNESS, COGNITIVE FUNCTION, AND DISABILITY STATUS IN MULTIPLE SCLEROSIS
Brian M. Sandroff,1 Lara A. Pilutti,1 Ralph H.B. Benedict,2 Robert W. Motl1 1Kinesiology and Community Health, University of Illinois at Urbana- Champaign, Urbana, IL; 2Department of Neurology, University at Buffalo, Buffalo, NY
Background: Cognitive impairment is a highly prevalent, poorly managed, and disabling consequence of multiple sclerosis (MS). Exercise training that improves physical fitness (ie, aerobic capacity and muscular strength) represents a promising approach for managing cognitive impairment in people with MS based on the gerontology literature. To date, there is limited evidence that physical fitness is associated with multiple domains of cognitive dysfunction (eg, impaired cognitive processing speed, verbal/visual memory) across the disability spectrum in people with MS. This is a precursory step before designing and testing exercise training interventions for improving cognitive function in MS.
Objectives: We examined the associations among aerobic capacity, lower-limb muscle strength, and cognitive functions in people with mild, moderate, and severe disability.
Methods: The sample included 63 individuals with mild (n = 21), moder- ate (n = 21), and severe (n = 21) MS disability based on a neurologic examination for deriving Expanded Disability Status Scale (EDSS) scores. The participants underwent neuropsychological assessments of cognitive processing speed (ie, Symbol Digit Modalities Test [SDMT]), verbal memory (ie, California Verbal Learning Test–2 [CVLT-2]), and visual memory (ie, Brief Visuospatial Memory Test–Revised [BVMT-R]). All participants further underwent testing for measuring aerobic capacity (ie, peak oxygen consumption) on a recumbent stepper (NuStep) and muscular strength (ie, peak torque of knee flexors and extensors) on an isokinetic dynamometer (Bio- dex).
Results: There were significant group differences in cognitive and fitness outcomes among individuals with mild, moderate, and severe disability. SDMT scores, but not CVLT- 2 or BVMT-R scores, were associated with aerobic capacity and muscular strength in the overall sample (r’s = 0.41– 0.49). SDMT scores were associated with aerobic capacity (r = 0.55) but not muscular strength (r’s = 0.33–0.40) in people with mild disability, and this association was attenuated, but remained statistically significant, after controlling for age as a covariate (pr = 0.41). SDMT scores were not associated with aerobic capacity or muscular strength in people with moderate (r’s = 0.04–0.06) or severe disability (r’s = 0.08–0.14).
Conclusions: These results indicate that disability status is a moderator of the association between aerobic capacity and cognitive processing speed, but not a moderator of physical fitness and memory outcomes. This supports aerobic exercise training for improving cognitive processing speed in people with mild MS, and further suggests that aerobic and resis- tance exercise training might not have as large an effect on cognitive function in people with moderate and severe MS disability.
Brian M. Sandroff,1 Lara A. Pilutti,1 Ralph H.B. Benedict,2 Robert W. Motl1 1Kinesiology and Community Health, University of Illinois at Urbana- Champaign, Urbana, IL; 2Department of Neurology, University at Buffalo, Buffalo, NY
Background: Cognitive impairment is a highly prevalent, poorly managed, and disabling consequence of multiple sclerosis (MS). Exercise training that improves physical fitness (ie, aerobic capacity and muscular strength) represents a promising approach for managing cognitive impairment in people with MS based on the gerontology literature. To date, there is limited evidence that physical fitness is associated with multiple domains of cognitive dysfunction (eg, impaired cognitive processing speed, verbal/visual memory) across the disability spectrum in people with MS. This is a precursory step before designing and testing exercise training interventions for improving cognitive function in MS.
Objectives: We examined the associations among aerobic capacity, lower-limb muscle strength, and cognitive functions in people with mild, moderate, and severe disability.
Methods: The sample included 63 individuals with mild (n = 21), moder- ate (n = 21), and severe (n = 21) MS disability based on a neurologic examination for deriving Expanded Disability Status Scale (EDSS) scores. The participants underwent neuropsychological assessments of cognitive processing speed (ie, Symbol Digit Modalities Test [SDMT]), verbal memory (ie, California Verbal Learning Test–2 [CVLT-2]), and visual memory (ie, Brief Visuospatial Memory Test–Revised [BVMT-R]). All participants further underwent testing for measuring aerobic capacity (ie, peak oxygen consumption) on a recumbent stepper (NuStep) and muscular strength (ie, peak torque of knee flexors and extensors) on an isokinetic dynamometer (Bio- dex).
Results: There were significant group differences in cognitive and fitness outcomes among individuals with mild, moderate, and severe disability. SDMT scores, but not CVLT- 2 or BVMT-R scores, were associated with aerobic capacity and muscular strength in the overall sample (r’s = 0.41– 0.49). SDMT scores were associated with aerobic capacity (r = 0.55) but not muscular strength (r’s = 0.33–0.40) in people with mild disability, and this association was attenuated, but remained statistically significant, after controlling for age as a covariate (pr = 0.41). SDMT scores were not associated with aerobic capacity or muscular strength in people with moderate (r’s = 0.04–0.06) or severe disability (r’s = 0.08–0.14).
Conclusions: These results indicate that disability status is a moderator of the association between aerobic capacity and cognitive processing speed, but not a moderator of physical fitness and memory outcomes. This supports aerobic exercise training for improving cognitive processing speed in people with mild MS, and further suggests that aerobic and resis- tance exercise training might not have as large an effect on cognitive function in people with moderate and severe MS disability.
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