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Motor, Cognitive, and Behavioral Performance in Middle-Aged and Older Adults With Multiple Sclerosis

Saymuah, Sara BS; Laird, Hayley BS; Nitta, Manon BA; Atalla, Mareena BA; Fritz, Nora E. PhD, PT, DPT, NCS

doi: 10.1097/TGR.0000000000000235
Aging With a Progressive Neurologic Disease
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Age-related changes in motor function from young to old age in persons with multiple sclerosis (MS) have been well-documented. However, little is known about motor, cognitive, and behavioral differences between middle-aged and older adults with MS, and global relationships among motor, cognitive, and behavioral factors in persons with MS. In this study, we recruited ambulatory middle-aged and older adults with MS to complete walking, dual-task, cognitive, and survey measures. We found no differences in performance between groups in our sample of mildly disabled individuals with MS, suggesting that individuals with mild disease may have reduced age-related declines in motor function.

Neuroimaging and Neurorehabilitation Laboratory (Mss Saymuah, Laird, Nitta, and Atalla and Dr Fritz) and Program in Physical Therapy and Department of Neurology (Dr Fritz), Wayne State University, Detroit, Michigan.

Correspondence: Nora E. Fritz, PhD, PT, DPT, NCS, Wayne State University, 259 Mack Av, #2324, Detroit, MI 48201 (Nora.fritz@wayne.edu).

The authors gratefully acknowledge all of our participants as well as Carla Santiago for her assistance with study coordination and Eva Bernitsas, Bob Lisak, and Dequanna Johnson for assistance with participant recruitment.

The authors have disclosed that they have no significant relationships with, or financial interest in, any commercial companies pertaining to this article.

Multiple sclerosis (MS) is a progressive neurodegenerative disease marked by demyelination of the central nervous system, resulting in motor, cognitive, and behavioral impairments. The presentation of these symptoms can vary drastically, making it particularly challenging to predict the course of MS function over time and in the presence of aging. Individuals with MS are living longer; more than 90% of those diagnosed in their twenties will live to their seventies.1 As of 2015, older adults (<65 years) comprise a quarter of individuals with MS.2 Although increased cognitive impairment has been linked with increasing disability among individuals with MS,3 this relationship is also present among healthy older adults with normal aging.3 Thus, it has been difficult to attribute any acceleration in cognitive decline in older adults to an MS diagnosis alone. A better understanding of motor, cognitive, and behavioral aspects of MS in the context of natural aging is needed.

Older adults with MS experience age-associated pathological changes that can decrease the potential for axonal repair following an MS exacerbation, lead to a detrimental effect on motor ability, and negatively impact quality of life.4 Older individuals with MS may be more prone to motor disability than their younger counterparts due to reduced resilience of central nervous system axons to demyelination.5 Identifying differences in motor function between middle-aged and older adults with MS may help identify motor changes attributable to the aging process alone.

Interestingly, studies in healthy older adult populations and individuals with other neurologic diseases also indicate that gait changes may also be related to changes in cognitive function.6,7 Over time, healthy older adults demonstrated declines in walking and grip strength linked with both declines in cognition,8 specifically executive function and attention, as well as increased fall risk.9–12 Impairments in cognitive function, particularly processing speed, are common in individuals with MS.13–14 Some studies show that older adults with MS experience slower cognitive processing speeds, particularly in those who had fallen at least twice in a 12-month period compared with those who had not fallen or had fallen only once.14 However, another study suggests that cognition in older adults with MS was not affected any more than cognition in healthy older adults, and that the MS disease process did not exacerbate cognitive decline.5 Similarly, older adults demonstrate increased cognitive decline when compared with middle-aged adults, a finding that has been attributed to age-related decline in associative memory.15 Cortical atrophy has been linked to cognitive decline in persons with MS,16–19 and in healthy older adults, frontal lobe atrophy has been linked with impairments in balance, gait, and executive function.20 Indeed, executive function was a significant predictor of gait velocity over the course of aging,21 which may have implications for aging adults with MS.

Impairments in cognition are also linked with the ability to perform a motor and a cognitive task simultaneously (ie, dual-task performance).22 Individuals with intact cognition demonstrate greater gait stability, fewer falls, and less pronounced declines with dual-tasks.23 A decline in dual-task performance is typical with normal aging and may be indicative of cognitive decline.24 Increasing dual-task impairments in healthy older adults is marked by a slower gait when performing simultaneous cognitive tasks.6 In addition to slower gait, older patients diagnosed with MS demonstrate greater balance impairments and falls while performing dual-tasks when compared with healthy age-matched controls.25 Despite the link between poor dual-task performance and increased fall risk in MS,26–27 differences in dual-task ability between middle-aged and older adults with MS have not been explored.

Cognitive and motor decline in healthy older adults have been associated with subsequent decline in self-reported quality of life,28 which is linked to increased fatigue, increased pain, and decreased mobility.29 Among individuals with MS, increased reports of pain and lower quality of life have also been linked with poorer cognition,30 yet differences in these relationships between middle-aged and older adults with MS have not been explored.

Although prior work demonstrates that older adults with MS have greater motor disability than younger adults with MS,31 a better understanding of changes in performance from middle-aged (<55 years) to older adulthood (≥55 years) is needed. The objective of this study was to understand the differences in motor, cognitive, and behavioral performance between middle-aged and older adults with MS, as well as overall relationships among motor, cognitive, and behavioral performance in persons with MS. We hypothesized that older adults with MS would exhibit significantly more motor disability and lower quality of life compared with middle-aged adults. We did not anticipate, given previously published evidence, that cognitive decline would vary between these 2 groups. We further hypothesized that motor and cognitive performance would be significantly related among persons with MS and that lower quality of life would be linked with poorer motor performance. This knowledge could inform targets for physical rehabilitation and other interventions to improve the symptoms of individuals with MS.

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METHODS

Participants were included in the study if they had clinically definite MS as defined by the 2010 McDonald criteria,32 were 36 years and older, ambulatory with or without assistive equipment, stable on prescribed immunomodulatory therapy, and currently not experiencing an MS exacerbation or relapse. All procedures were approved by the Institutional Review Board at Wayne State University, and all participants signed an informed consent form prior to participation. Disease status was determined using the Patient Determined Disease Steps (PDDS), which has been shown to have concurrent validity with the Expanded Disability Status Scale (EDSS),33–36 and is recommended for use by North American Research Committee on Multiple Sclerosis Registry.37 Participants completed the following motor, cognitive, and behavioral tests in a single visit.

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Timed 25-Foot Walk

Participants walked at their quickest safe pace along a 25-foot walkway. Two trials were completed and averaged to obtain the final score. The Timed 25-Foot Walk (T25FW) has excellent interrater relatability, as well as excellent correlation with the EDSS.38 The T25FW was repeated with participants walking backward at a self-selected comfortable pace. Although the reliability and validity of backward walking in MS is not yet established, backward walking has been shown to be more sensitive to age-related declines in mobility and balance than forward walking in healthy adults.39

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Walking While Talking Test

The Walking While Talking Test (WWTT) has 3 components: In the first component, the participants walked 20 ft in one direction, turned, and walked 20 ft back to the start at a comfortable, self-selected walking pace. In the second component, the simple condition (ie, WWTT Simple), the participant walked the same track speaking the English alphabet aloud. In the third component, the complex condition (i.e., WWTT Complex), the participant walked the same track while speaking every other letter of the alphabet beginning with “B.” Participants then performed the cognitive tasks while sitting, first speaking the alphabet aloud, and then speaking every other letter of the alphabet beginning with “A.” The WWTT is a useful test of dual-task ability in older adults,40 and poor performance (ie, longer time to complete these walks) on the both the simple and complex conditions is strongly predictive of falls over 12 months in older adults41; however, reliability and validity data are not yet available for persons with MS. Gait and cognitive dual-task effect (DTE), a quantification of the change in performance under dual-task conditions relative to the single-task condition, was calculated using the methods of Plummer and Eskes.42

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Activities-specific Balance Confidence Scale

This 16-item questionnaire asks participants to rate their level of confidence in their ability to not sustain a fall or become unsteady while performing a variety of tasks, such as reaching for an object while standing on a chair or walking in a crowded mall as people are rapidly walking past. Higher scores indicate greater balance confidence, while lower scores indicate decreased balance confidence. The Activities-specific Balance Confidence Scale (ABC) has been shown to be valid in persons with MS.43

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Symbol Digit Modalities Test

The Symbol Digit Modalities Test (SDMT) measures the cognitive domain of information processing speed. The participants were given a key with 9 numbers each corresponding to a symbol, as well as a page of symbols. The participant was instructed to say aloud the number corresponding with each symbol on the page, completing as many as possible in 90 seconds.44 The SDMT has been shown to be both a valid measure of cognitive performance and particularly sensitive to slowed information processing speed in persons with MS.45

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Stroop Task

The Stroop Task was used to measure executive function and response inhibition. The test has 3 components, each lasting 45 seconds. For the first task, the Stroop Color, participants were shown a page of colored blocks and asked to name the color of the blocks. In the second task, the Stroop Word, participants read the names of colors printed in black and white. In the third task, the Stroop Interference, participants were shown a page with color names printed in incongruent colors, and asked to say aloud the color of the ink in which the word was printed.46

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Multiple Sclerosis Quality of Life-54

The Multiple Sclerosis Quality of Life-54 (MSQOL-54) is a 54-question survey that evaluates physical and mental well-being in the context of MS-specific impairments. This test has been shown to relate to MS symptom severity, level of ambulation, employment limitations due to health, and depressive symptoms.47

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Brief Pain Inventory

The Brief Pain Inventory (BPI) asked participants to assess pain severity and the degree to which pain interferes with daily functioning. This 12-item measure is both a reliable and valid measure of pain severity and interference in persons with MS.48

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Fall history

Participants were asked to report falls (ie, landed on the ground or lower surface) and near-falls (ie, a trip or stumble that would have resulted in a fall had they not grabbed hold of something stable) in the past month and the past 6 months. The number of reported instances for both falls and near-falls was recorded.

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Statistical analyses

All statistical analyses were performed with SPSS Version 24 (IBM, Armonk, New York). Outliers assessed with box and whisker plots. Normality of data assessed with Shapiro-Wilk tests; assumptions for normality were not met, so nonparametric statistics were utilized. To determine differences between middle-aged and older adults with MS, Mann-Whitney tests were performed, and a 2 × 2 χ2 analysis was used to determine differences in gender between groups. To assess associations among motor, cognitive, and behavioral measures, spearman correlations were utilized at both the whole-group and within-group levels.

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RESULTS

Twenty-nine individuals (mean (standard deviation) age: 50.9 (9.2) years, symptom duration: 14.8 (10.3) years, and median (interquartile range) PDDS: 2 (3), and sex: 6 males, 23 females) with MS volunteered for this study. Individuals aged 35 to 54 years were considered middle-aged, while individuals 55 years and older were considered older adults, consistent with other studies of older adults with MS.49–53 No outliers were removed, and performance on motor, cognitive, and behavioral tasks for both groups is reported in Table 1.

TABLE 1

TABLE 1

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Between-group analysis

Middle-aged and older adult groups demonstrated no significant differences in sex, body mass index, education level, disease severity, or disease duration (P < .05). There were no significant differences in performance on the T25FW in either the forward or backward directions, nor on the WWTT. Although the middle-aged group reported more falls over both the past month and the past 6 months and the older adult group reported more near-falls, these differences were not significant (P < .05). Furthermore, the groups did not report significantly different balance confidence ratings on the ABC. The groups did not perform significantly differently on the SDMT or Stroop cognitive tests. Of interest, the older adult group rated their mental quality of life on the MSQOL as significantly higher than the middle-aged group, but there were no differences in physical quality of life on the MSQOL or pain ratings on the BPI (Table 1).

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Whole-group analysis

Relationships among motor and cognitive factors

Greater balance confidence and better performance on walking and dual-task tests were strongly related to better performance on cognitive tests of information processing speed and executive function. Specifically, forward and backward walking, WWTT Simple and Complex, and ABC were all significantly correlated with SDMT and Stroop Interference scores (Table 2). Backward walking and self-reported falls at 1 month, while also strongly correlated with SDMT and Stroop Interference, were also strongly related to Stroop Color and Stroop Word performance. Falls at 6 months and near-falls were not related to any of the cognitive factors. In addition, better performance on backward walking was also strongly related to better balance confidence (r = −0.567; P = .001) and better dual-task performance on simple (Figure 1) and complex tasks (r = 0.829; P < .001).

TABLE 2

TABLE 2

Figure 1

Figure 1

Better performance on both forward and backward walking tests was related to fewer reports of falls at 1 month (r = 0.515; P = .004, and r = 0.479; P = .009, respectively) and 6 months (r = 0.480; P = .008, and r = 0.430; P = .020, respectively). Similarly, better performance on simple and complex dual-tasks was strongly correlated with reports of fewer falls at 1 month (WWTT Simple: r = 0.472; P = .010, and WWTT Complex: r = 0.466; P = .011) and 6 months (WWTT Simple: r = 0.393; P = .035, and WWTT Complex: r = 0.430; P = .020). None of the walking tests were significantly associated with near-falls.

We evaluated the calculated DTE for gait and cognitive conditions on both the WWTT Simple and Complex (Figures 2A and 2B). During the WWTT Simple, the majority of individuals experienced mutual interference, where performance in both gait and cognition declined; however, several individuals prioritized gait, while several others prioritized the cognitive task. Interestingly, when confronted with the WWTT Complex, no individuals prioritized the cognitive task and there is a marked shift to an increased prioritization of gait. This suggests that the cognitive condition was more demanding for individuals.

Figure 2

Figure 2

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Relationships among behavioral factors and motor and cognitive factors

Better performance on forward and backward walking was significantly related to better physical quality of life on the MSQOL physical subscore (r = −0.467; P = .011, and r = −0.434; P = .019, respectively), but was not linked to mental quality of life on the MSQOL mental subscore, or pain severity or interference. Better performance on both simple and complex dual-tasks was strongly related to better physical (WWTT Simple: r = −0.593; P = .001, and WWTT Complex: r = −0.603; P = .001) and mental (WWTT Simple: r = −0.473; P = .010, and WWTT Complex: r = −0.509; P = .005) quality of life, but not pain severity or interference. Similarly, better balance confidence on the ABC was also linked with fewer falls at 1 month (r = −0.499; P = .006) and 6 months (r = −0.461; P = 0.012) as well as better walking performance (forward: r = −0.619; P < .001, and backward: r = −0.567; P = .001) and better dual-task performance (WWTT Simple: r = −0.634; P < .001, and WWTT Complex: r = −0.619; P < .001). Finally, better forward and backward walking performance was also strongly linked to better dual-task performance on both simple (forward: r = 0.884; P < .001, and backward: r = 0.886; P < .001) and complex (forward: r = 0.872; P < .001, and backward: r = 0.829; P < .001) tasks.

Better physical quality of life was strongly correlated with fewer self-reported falls at both 1 month (r = −0.489; P = .007) and 6 months (r = −0.513; P = .004) as well as fewer near-falls at 1 month (r = −0.486; P = .009) and 6 months (r = −0.373; P = .046), yet mental quality of life and pain severity and interference were unrelated to falls. Better balance confidence on the ABC was linked not only with better mental and physical quality of life (r = 0.622; P < .001, and r = 0.545; P = .002, respectively), but also to lower pain interference (r = −0.377; P = .044).

Neither SDMT nor any part of the Stroop was significantly related to quality of life or pain in this cohort.

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Within-group analysis

Middle-aged adults

Relationships among motor and cognitive factors

Better performance on the SDMT was associated with better performance on forward (r = −0.486; P = .035) and backward walking (r = −0.602; P = .006) as well as reports of fewer falls in the past month (r = −0.477; P = .039) and better balance confidence (r = 0.661; P = .002).

Better performance on Stroop Interference, while also related to better forward (r = −0.668; P = .002) and backward (r = −0.710; P = .001) walking, fewer reports of falls in the past month (r = −0.464; P = .045) and better balance confidence (r = 0.749; P < .001), was also related to better performance on both simple (r = −0.697; P = .001) and complex (r = −0.535; P = .018) dual-tasks. Consistent with whole-group analyses, only better backward walking performance and higher balance confidence on the ABC were related to better Stroop Color (backward: r = −0.528; P = .020, and ABC: r = 0.719; P = .001) and Stroop Word (backward: r = −0.505; p=0.027, and ABC: r = 0.612; P = .005) performance.

Fewer reports of falls at both 1 and 6 months were associated with better forward (1 month: r = 0.680; P = .001, and 6 months: r = 0.600; P = .007) and backward (1 month: r = 0.577; P = .010, and 6 months: r = 0.578; P = .010) walking, better performance on simple (1 month: r = 0.590; P = .008, and 6 months: r = 0.585; P = .009) and complex (1 month: r = 0.572; P = .011, and 6 months: r = 0.562; P = .012) dual-tasks, and better balance confidence (1 month: r = −0.714; P = .001, and 6 months: r = −0.603; P = .006). None of the walking tests were significantly related to near-falls.

We evaluated the DTE for the WWTT Simple and Complex within group. During the WWTT Simple, middle-aged individuals aligned with the whole-group data; the majority experienced mutual interference, while some prioritized gait and others prioritized cognition (Figure 2C). During the WWTT Complex, the middle-aged group followed the same pattern as the whole-group data (Figure 2B).

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Relationships among behavioral factors and motor and cognitive factors

Better physical and mental quality of life, as measured by the MSQOL subscores, were strongly associated with better performance on forward (r = −0.719; P = .001, and r = −0.692; P = .001) and backward (r = −0.616; P = .005, and r = −0.682; P = .001) walking, as well as better performance on simple (r = −0.788; P < .001, and r = −0.786; P < .001) and complex (r = −0.756; P < .001, and r = −0.768; P < .001) dual-tasks and better balance confidence (r = 0.614; P = .005, and r = 0.575; P = .010). Lower physical quality of life was significantly associated with higher numbers of reported falls at 1 (r = −0.583; P = .009) and 6 months (r = −0.573; P = .010). However, reported falls were not related to mental quality of life, and near-falls were not related to either mental or physical quality of life.

Only forward walking was significantly associated with pain severity (r = 0.478; P = .038), but higher pain interference was related to poorer forward (r = 0.546; P = .016) and backward (r = 0.535; P = .018) walking performance as well as worse performance on simple (r = 0.509; P = .026) and complex (r = 0.496; P = .031) dual-tasks and poorer balance confidence (r = −0.497; P = .030). Neither falls nor near-falls were significantly associated with pain severity or interference in middle-aged adults with MS.

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Older adults

Relationships among motor and cognitive factors

Poorer cognitive performance on the SDMT and Stroop Interference was associated with poorer performance on motor tests and poorer balance confidence ratings, but none of these relationships were significant in the older adult cohort.

In the older adult group, reported falls and near-falls were not significantly associated with walking, dual-task performance, or balance confidence ratings.

We evaluated the DTE for the WWTT Simple and Complex within group. During the WWTT Simple, older adults with MS demonstrated a different pattern from the whole-group results. No individuals prioritized gait during the dual-task condition; rather, they prioritized the cognitive task or experienced mutual facilitation (ie, a relative improvement in both gait speed and cognitive performance under dual-task conditions) (Figure 2D). During the WWTT Complex, the older adult group followed the same pattern as the whole-group data (Figure 2B).

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Relationships among behavioral factors and motor and cognitive factors

Better balance confidence was significantly associated with better physical quality of life (r = 0.661; P = .038) in the older adult cohort. Mental quality of life and pain severity and interference were not significantly associated with walking or dual-task performance in this older adult group. Reports of near-falls at 1 month were strongly correlated with mental (r = −0.901; P = .001) and physical (r = −0.682; P = .043) quality of life in older adults with MS. Near-falls were not related to pain ratings, nor were fall reports related to either quality of life or pain.

None of the cognitive measures were related to quality of life or pain in the older adult group.

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DISCUSSION

Previous work demonstrates that motor decline is intensified by aging in MS.3 Interestingly, we found no significant differences in motor performance between our middle-aged and older adult groups. While it is possible that motor declines are reduced in persons with mild disability, there is also the potential that age-related changes in motor performance among persons with MS may occur between the younger adult and middle-aged groups. However, further studies with greater sample sizes are needed to identify differences in motor decline among younger, middle-aged and older adults with MS.

There were also no significant differences between groups in cognitive performance, which aligns with literature showing that magnitude of cognitive impairments among individuals with MS does not vary across the lifespan.5 Our results show that poorer performance on cognitive tests of processing speed (ie, SDMT) was associated with poorer performance on forward and backward walking as well as greater reports of falls and poorer balance confidence. This builds upon work detailing the relationship among motor performance, cognitive performance, and fall risk in persons with MS14 and healthy older adults.6–12 We also show that better performance on the Stroop Interference test is related not only to better performance on forward and backward walking tests, fewer reports of falls, and better balance confidence, but also to better performance on simple and complex dual-tasks. The Stroop Interference test requires individuals to inhibit their immediate response and prioritize the color of the ink rather than reading the word itself, which is similar to dual-task performance where the individual must balance the demands of the walking and cognitive tasks simultaneously. The connection of Stroop Interference to clinical dual-task performance builds upon prior work highlighting the link among dual-task performance and fall-risk in persons with MS26–27 and healthy older adult fallers.54 The utility of examining motor and cognitive tests simultaneously is also highlighted by the DTE results shown in Figure 2. Differences in prioritization between the WWTT Simple and Complex conditions demonstrate the importance of including varying levels of cognitive complexity. The differences seen visually between middle-aged and older adults (Figures 2C and 2D) suggest that older adults may prioritize cognitive tasks during dual-tasks, which could lead to greater fall risk, though this should be examined further in a larger sample.

Clinical tests of walking and balance are often used to determine fall risk in healthy older adults and persons with MS. Indeed, backward walking has been linked with fall risk in healthy older adults.39 While backward walking performance has been shown to decline in individuals with MS compared with controls,55 our results show a significant correlation between poorer performance on backward walking and lower balance confidence on the ABC as well as more self-reported falls and near-falls. This indicates the potential significance of considering backward walking as a determinant of fall risk in persons with MS in future studies.

Although prior work suggests that older adults with MS exhibit greater declines in mental and physical quality of life related to greater physical and mental decline, our results did not show differences among middle-aged and older adults with MS. This is perhaps not surprising, given that we also did not find significant differences in motor or cognitive performance between groups. It is likely that these age-related declines are reduced in mildly disabled individuals with MS. In whole-group analysis, we were also surprised to find that cognitive performance on the SDMT and Stroop was not significantly related to quality of life on the MSQOL. This differs from our earlier findings30 in which poorer SDMT performance was highly correlated with both lower mental and physical MSQOL. This discrepancy is perhaps due to the wider range of disability levels and lower performance on the SDMT seen in our previous study. Our data also demonstrated a significant relationship between higher mental and physical quality of life and better performance on simple and complex dual-tasks. This is in agreement with recent work showing that the dual-task cost of standing balance is linked with quality of life in individuals with an EDSS less than 3.0.56

This study was limited by a small sample size as well as a smaller cohort of older adults with MS compared with middle-aged adults. Importantly, our convenience sample included individuals with low disability (indeed, 34.5% of individuals [10/29] ranked themselves as “no disability”), which limits the generalizability of our findings and impacts our ability to determine motor findings specifically attributable to aging. In addition to age and disease severity, there are other factors such as fatigue, depression, and spasticity that may impact motor, cognitive, and behavioral performance. As these factors were not evaluated, we are unable to determine their impact on the study results. We limited this study to ambulatory individuals with MS and are unable to generalize the findings to nonambulatory individuals. Our convenience sample included individuals with high education levels (the average was completion of college), which may also impact the results and limit generalization to all MS populations. Education level also contributes to cognitive reserve theory,57 which has been shown to moderate the effect of MS on cognitive functioning58 and may provide protection against disease-related declines in function. Whole-group findings of relationships among motor and cognitive performance persist in within-group analysis of the middle-aged group, but are not present in the older adult group. This may be a result of small sample sizes, or due to our older adult group being largely younger than 65 years, when age-related changes may not yet be apparent. We noted that the r values for correlations among motor and cognitive function were similar to the middle-aged and whole-group analysis, but did not reach significance. Future studies should focus on simultaneous comparison of young, middle-aged, and older adults with mild, moderate, and severe disability levels to assess age-related motor or cognitive decline across the disability spectrum. Once the age of first decline has been identified, additional studies may assess other factors for exacerbation or improvement of motor and cognitive decline in persons with MS.

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CONCLUSIONS

In our cohort of mildly disabled (PDDS <2) middle-aged and older adults with MS, motor, cognitive, and behavioral performance remained stable and were not impacted by aging. Our data demonstrate that backward walking may be an important factor for understanding fall risk, while the Stroop Interference cognitive test is important for understanding dual-task deficits in persons with MS. Clinicians should consider including backward walking and Stroop Interference to their evaluations of persons with MS to assess fall risk and potential dual-task deficits. Future work to elucidate motor, cognitive, and behavioral declines across the disability and aging spectrum is needed to foster the development of novel rehabilitation paradigms for persons with MS.

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Keywords:

accidental falls; age factors; cognition; gait; multiple sclerosis; pain; quality of life

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