Practice Points
- Despite a lack of a quantitative relationship between interoceptive awareness and emotional susceptibility and fatigue, patients with multiple sclerosis cite the physical and emotional aspects of fatigue as factors in physical activity choices.
- Understanding a patient or client’s experience with fatigue, in both a physical and emotional sense, could be critical to understanding their physical activity choices. These topics need to be discussed when beginning a physical activity regimen.
Multiple sclerosis (MS) is an autoimmune disorder that affects more than 2 million people globally.1 It results in demyelination of nerves, changes in brain mass and functional connectivity, and downstream physiologic effects such as muscle weakness. Quality of life for people with MS is often low because of sensory loss, impairment in motor and visual function,1 and psychobiological changes such as the emergence of pain2 and cognitive impairments.3
Fatigue, a particularly debilitating symptom for people with MS, is negatively associated with quality of life.4 Fatigue has been highly studied in people with MS in the physical and mental domains. Large variability in reported fatigue levels, within individuals and days,5 adds to the complexity of fatigue in MS. Fatigue can be positively affected by lifestyle factors such as regular exercise,6 but physical activity levels in people with MS remain lower than those in nondiseased groups.7
Interoception in people with MS may contribute to fatigue and the impact of fatigue symptoms.8 Interoception is “perception of the physiological condition of the entire body.”9 Differences in activity in brain areas that process interoception, such as the insula and the anterior cingulate cortex, in people with MS compared with those without MS have been associated with increased reported fatigue.10
Broad personality traits such as neuroticism, which is part of the Big Five model of personality, are well researched in MS.11,12 People with MS are often characterized by above-average neuroticism; those with high neuroticism are likely to experience negative affect, including excessive worry, negative responses to environmental stressors, and feeling overwhelmed by objectively minor frustrations.13 Neuroticism has also been linked to fatigue among people with MS.14–16 A novel aspect of the present investigation is the focus on emotional susceptibility specifically rather than on the broader dimension of neuroticism. Emotional susceptibility is a perceived reduced ability to control reactions in situations of danger or threat and results in higher emotional reactivity to stimuli,17,18 including feelings of helplessness, discomfort, inadequacy, and vulnerability. Emotional susceptibility is a distinct and narrow psychological concept that is less well understood in people with MS and is a factor that may contribute to experiences of fatigue.
Although links between interoception and emotion,11 as well as between fatigue and personality,12,13 have been made, associations among interoception, emotional susceptibility, and fatigue have not yet been explored. Investigating potential relationships among these constructs may increase our understanding of MS fatigue, perhaps leading to the development of interventions to improve this experience. This information could be particularly useful to exercise practitioners who wish to work with people with MS who deal with fatigue. This study evaluates the fatigue experience in relation to emotional susceptibility and body sensations in people with MS to investigate whether there is a relationship between fatigue, interoceptive awareness, and emotional susceptibility in people with MS, when accounting for demographic variables, physical functional levels, and leisure-time physical activity. Both quantitative and qualitative methods were selected to provide a richer assessment.
Methods
Study Design
This study used a mixed-methods, single-group observational design. The purpose of the mixed-methods approach is triangulation,14 which focuses analyses on areas where qualitative and quantitative results converge or diverge.14 The typology is a partially mixed sequential equal status design.15 Eligible participants completed surveys that collected information on demographics, fatigue, interoceptive awareness, and emotional susceptibility. A subset of participants completed an optional qualitative interview that asked open-ended questions concerning fatigue, interoceptive awareness, and emotional susceptibility. Interpretive tradition is used to qualitatively address the research question.15
Participant Selection
Participants were recruited through community and national advertisements and word of mouth. Inclusion criteria were a medical diagnosis of MS, age 18 to 65 years, and answering “yes” to the question “Would you consider yourself to be physically active?” Exclusion criteria included lack of access to a reliable internet connection or phone for the survey and interview administration. Eligible participants provided informed consent before data collection. This study was approved by the University of Georgia institutional review board.
Data Collection
Quantitative Data Collection
Demographic information collected included age, sex, race, an index of walking function assessed by the Patient-Determined Disease Steps (PDDS) scale,16 and habitual leisure-time physical activity assessed by the Godin Leisure-Time Exercise Questionnaire (GLTEQ).17 Physical function and physical activity were assessed because of their known association with fatigue in MS samples.18
Fatigue was measured using the Fatigue Severity Scale (FSS),19 a 9-item scale to assess the degree to which fatigue interfered with life functioning during the past week. Responses are measured on a scale from 1 (strong disagreement) to 7 (strong agreement).
Interoceptive awareness was measured using the Multidimensional Assessment of Interoceptive Awareness, Version 2 (MAIA-2),20 a 37-item scale with 8 subscales: noticing, not-distracting, not-worrying, attention regulation, emotional awareness, self-regulation, body listening, and trust. Participants answered items on a Likert scale ranging from 0 (never) to 5 (always), with higher scores indicating more interoceptive awareness.
Emotional susceptibility was measured using the Emotional Susceptibility Scale (ESS).21, 22 This 40-item scale measures susceptibility to emotions (eg, Sometimes I cry for no reason; I feel down when others don’t approve of me). Participants responded to items on a 6-point Likert scale anchored at 1 (completely false for me) and 6 (completely true for me), with higher scores indicating more emotional susceptibility. One item was discarded from overall scoring because it relates specifically to fatigue and could have confounded correlational analyses involving fatigue questionnaires.
Qualitative Data Collection
After completion of the surveys, semistructured23 phone interviews approximately 1 hour in duration were used to collect qualitative data on participants’ perceptions of fatigue. Interview questions focused on bodily sensations and emotions experienced with fatigue, perceptions of the meaning of the sensations and emotions, how these factors collectively affected personal activity choice, how these factors shape confidence and self-efficacy, and perspectives on the experience of fatigue as positive or negative feedback from the body. The audio recordings were used to create interview transcripts for analysis. All interviews and transcriptions were performed by the first author (M.W.).
Data Analysis
Quantitative Data Analysis
Quantitative data analysis was performed using IBM SPSS Statistics for Windows, version 26.0 (IBM Corp). Beyond descriptive statistics, individual FSS scores were regressed on the MAIA-2 and ESS scores in a multivariate linear regression model to assess the magnitude and direction of the associations. Individual demographic data (ie, age, sex, race) and PDDS scale and GLTEQ scores were used as control variables (covariates).
Qualitative Data Analysis
Qualitative data analysis was conducted after the interviews were transcribed. Transcriptions were deidentified, pseudonyms were provided, and other identifying information (eg, names, locations) was replaced with generic terms (eg, doctor). An inductive thematic analysis24 was performed by coding interviews, a process using verbatim quotes from the transcripts as a unit of analysis, as per standard protocol in qualitative analysis.25 Similar codes from each interview were placed into categories, which spanned across interviews. Categories were grouped into themes, or primary outcomes of the qualitative portion of this study. Reflexivity,26 or proximity of the researcher to the participant, was considered during analysis and interpretation of interview data due to some participants’ involvement in previous research. Analyses were completed using Atlas.ti 9 for Windows (ATLAS.ti Scientific Software Development GmbH). Independent t tests compared baseline demographics of those who completed both the quantitative and qualitative portions and those who completed only the quantitative portion of the study to ensure that the samples did not differ.
Results
Participants
Fifty-five participants completed quantitative data collection for this study. Participant demographic characteristics are provided (Table 1). The sample had a mean ± SD age of 48.1 ± 11.7 years and was overwhelmingly female (78.2%) and White (83.6%). The mean ± SD PDDS scale score was 2.1 ± 1.8, indicating a more functional sample. Mean ± SD GLTEQ scores indicated that this sample had a wide range of physical activity levels (25.8 ± 22.4; range, 0–91). The optional qualitative interview was completed by 35 participants. T tests revealed no significant differences between the demographic characteristics of the participants in the qualitative interviews and the total group (data available on request).
Quantitative Results
Mean ± SD FSS, MAIA-2, and ESS scores were calculated for the sample. The mean ± SD FSS score in this sample (5.0 ± 1.3) was higher than that in the healthy population and higher than 4.0, indicating problematic fatigue, enough to interfere with daily functioning. More than three-quarters of the sample (76.4%) fit this category. Mean ± SD MAIA-2 (2.8 ± 0.6) and ESS (3.0 ± 1.0) scores were low compared with normative values.
There were no statistically significant effects of MAIA-2 and ESS scores on FSS scores before controlling for age, sex, race, PDDS scale scores, and GLTEQ scores (β = −0.16, P = .25 and β = 0.15, P = .27, respectively). The PDDS scale score was significantly related to fatigue (β = 0.34; P = .01).
Qualitative Results
Inductive coding and thematic analysis revealed 4 themes: body sensations experienced with fatigue, emotions experienced with fatigue, mind-body connection, and impact of fatigue on physical activity.
Body Sensations Experienced With Fatigue
Participants identified types and locations of body sensations felt when fatigued, leading to these dimensions being used as subthemes of the body sensations theme (Figure S1, available online at IJMSC.org). Frequently reported whole-body sensations included pain, heaviness, tingling, and numbness. A “pins and needles” sensation was most reported in the hands and feet. Feelings of drowsiness and “swimming” were described in the head. Participants also noted subjective increases and decreases in heart rate during fatigue. Participants recognized that fatigue caused differences in how they perceived these sensations. For example, Heather said, “Sensation kind of…becomes…not apparent but noticed at that time. You’re not purposefully ignoring it.” Kelly corroborated: “Just different things like that seem to…become louder or they become more pronounced. Um, with the fatigue…if you feel better…you know that you can deal with uh, a certain pain that you might have reached.”
Emotions Experienced With Fatigue
Emotions related to experiencing fatigue were categorized into subthemes related to emotional susceptibility and not related to emotional susceptibility (Figure S2). Many emotions were identified as related to emotional susceptibility (98 codes); however, the most frequently discussed single emotion across participants was frustration (23 codes), which is not related to the definition of emotional susceptibility. For example, Kathy said, “Frustrating. It’s frustrating. I’m more...um resigned to it I guess than I was in the beginning, but it’s still frustrating to me.” Frank said, “Yeah, the tiredness, um, frustrating, like I said, I don’t know what else I could uh…how I could put that. I don’t get sad; I don’t get sappy.” Most participants felt that fatigue amplified emotions. For example, Nicole said, “More, more intense, yeah. Or even more like more…present.” Leslie described it, “My emotions are probably a little rawer when I am fatigued.”
Mind-Body Relationship
Participants discussed their perception of the mind-body relationship, which was divided into subthemes of mind-body connection (a perception of mind and body reflecting similar conditions) and mind-body mismatch (a perception of mind and body reflecting dissimilar conditions) (Figure S3). Most participants (n = 25) discussed a mismatch between their thoughts and body sensations. For example, Tina said, “It’s a different type of fatigue where your body, your brain can say, ‘OK, I’m going to get up on 1, 2, 3,’ but your body says, ‘Not happening.’” June added, “I wanna say like, a, it’s, everything kind of goes together, but I, like I mean, I know sometimes I have to push through and my mind is saying, ‘You gotta, you gotta, you gotta do this,’ but my body’s just like ‘No.’” These subthemes were not mutually exclusive; both connection and mismatch could be present. For example, Veronica said, “I process this (fatigue) and I notice that it’s happening, but at the same time I spend way too much time just ignoring how I feel and pushing through. There are some times when I’m so caught up in the day that I don’t recognize the fatigue until later.”
Impact of Fatigue on Physical Activity
Participants identified ways in which the fatigue experience, including emotions, affected physical activity. This was divided into subthemes of exercise time (duration), type, and frequency (Figure S4). Amy discussed the effect on exercise type: “It definitely impacts choices because it’s that, you know, which one’s gonna make the most sense. The idea of like having to get in the car and like find a thing, and do the hike, do the thing, and like go hiking—which I would love to do—it’s just, that’s not a feasible choice as much anymore.” Regarding exercise time (duration), June said, “I take my time at the gym, like I give myself 2 hours. It’s not like I’m, you know, rushing through. But I can’t do the fast [things] like I used to. I take things a lot slower.” Many participants weaved together the discussion of exercise time, type, and frequency in the context of a fatigued state. For example, Frank said, “How often I’m working out, you know, it’s 2 hours that, that 2 hours I know it’s, it’s what I can do. Whether it’s yoga or stretching or biking or, or lifting or, you know, working, working on my legs, I, I’ve noticed there is a certain amount of time of physical activity that I’m gonna shut down.”
Mixed-Methods Comparisons
Triangulation was not achieved for all aspects of the quantitative and qualitative results. There was dissonance between the quantitative measurement of fatigue and the interoceptive awareness and qualitative discussion of those constructs and in the discussion about the impact of body sensations and emotions on physical activity. Emotional susceptibility results, however, were similar in the quantitative and qualitative data (Table 2).
This sample had a low mean interoceptive awareness scale score (2.8), and many participants discussed how connected they felt within their own body. Participants identified specific body sensations that came with fatigue. Although this does not indicate the accuracy of these perceptions, it does suggest that some participants were interoceptively aware of fatigue, based on the aforementioned definition (“perception of the physiological condition of the entire body”9). However, quantitative assessment of interoceptive awareness does not indicate a higher level of interoceptive awareness in this sample.
Although participants identified a range of emotions, some of them were the same as or similar to those of the construct definition of emotional susceptibility (ie, helplessness, discomfort, inadequacy, vulnerability). When examined by frequency, feelings of frustration while fatigued were more common, indicating that the response of the sample did not fully overlap with the emotions identified in the emotional susceptibility construct.
The fatigue experience—the body sensations and emotions felt during fatigue—affected physical activity. Participants described the fatigue experience as a barrier to exercise or as a reason to modify exercise planning. Quantitative data in this sample, however, does not indicate a significant relationship between GLTEQ scores and any of the observed aspects of the fatigue experience.
Discussion
Most studies have used either quantitative questionnaires27 or qualitative interviews28,29 to evaluate fatigue in people with MS; 1 previous study used mixed-methods analysis to better understand fatigue management.30 The use of mixed methods in the present study allowed for an in-depth exploration of the way people with MS experience fatigue and indicates that there could be nuances to fatigue that quantitative measurement alone does not capture. To understand how a person with MS experiences fatigue more fully, clinicians should consider routinely asking questions related to how fatigue manifests itself both physically and emotionally. This kind of inquiry could be especially important for areas of behavior change that are likely to shift with fatigue levels, such as the adoption of greater physical activity or a formal exercise program.
In the physical activity or exercise context, screening and monitoring materials for maintenance programming or intervention should include more qualitative questioning. Efforts in this area could lead to more individualized programming as participants begin new regimens. For example, if fatigue creates feelings of numbness in the feet, a practitioner could adjust a daily program by doing standing exercises first or incorporating more sitting exercises. Adjustments of this type might increase adherence by creating more movement options, but they also could decrease the risk of adverse events that would reduce adherence and could cause participants to avoid exercise interventions altogether.
Similarly, if practitioners are more fully aware of the emotions that fatigue can create, motivation techniques could be tailored to address those feelings, including those associated with the fear-avoidance model relating fear, inactivity, and pain.31 Many participants said in the interviews that they had not been asked questions of this type by practitioners. In the context of this study, participants responded to questions of this kind with valuable detail. Practitioners can investigate emotional responses to fatigue by asking how being fatigued feels emotionally, how those emotions might change with the setting of the activity, (eg, whether fatigue is brought on when running through a park vs exercising in a busy gym), and how fatigue severity affects the emotions experienced (eg, increasing the intensity of the emotion). Over time, a practitioner would become more familiar with the participant’s needs and could shape long-term exercise plans around those needs. For example, if fatigue makes a participant feel anxious, especially in a public setting such as a gym, a practitioner could “plan around” the participant’s emotional reaction to fatigue by having them exercise in a smaller room or a private setting.
The dissonance between the quantitative measurement of fatigue and the qualitative descriptions of fatigue could be explained in several ways. For example, the content of 5 of the 9 FSS items focused on the degree to which fatigue interferes with life functioning. Hence, high agreement between objective measures of fatigue and the subjective ratings of the FSS is not expected unless fatigue interferes with life function in a dose-dependent manner and other variables do not influence this relationship. Variables unaccounted for in this study, such as depression symptoms, are also fatigue-related interference.32 The body of mechanistic literature indicates that increased levels of fatigue are associated with interoceptive abnormalities or deficits,33 and this sample reported high levels of fatigue. Possibly, this sample’s higher levels of fatigue could have impaired interoceptive awareness, and the expressed perception of a mind-body connection is the result of an inaccurate interpretation. The specificity of qualitative discussion of body sensations in this sample did not translate to the quantitative assessment of interoceptive awareness, evidenced by the low mean MAIA-2 scores. Whereas the mechanistic literature has focused on interoceptive accuracy in people with MS, little effort has been made to comprehensively assess perceived interoceptive awareness; therefore, it is unclear whether this sample is comparable in interoceptive awareness to larger samples of people with MS.
Qualitative evidence indicating body sensations as part of the fatigue experience echoes the results of other qualitative work in people with MS.34,35 However, this finding contrasted with the low scores for interoceptive awareness from the quantitative measurements. Dissonance in quantitative measurement and qualitative discussion of interoceptive awareness could be because of the specificity of the situation (ie, qualitative probing of awareness of sensations in a fatigue setting vs quantitative assessment of awareness in general). The quantitative data collected could point to a baseline value, and the perception of awareness may be heightened with fatigue. Another qualitative investigation of fatigue in women with MS described heightened feelings of physical strain during fatigue.36 Also note that this discrepancy could result from limitations in the conceptualization of interoceptive awareness and its assessment using the MAIA-2. A systematic review of interoceptive measures concluded that interoceptive measures have “low overall convergence and interrelationships between questionnaire items. This observation mitigates the interpretation and replicability of the findings in self-report interoception research.”37 Investigators should examine interoceptive awareness using multiple measures in a sample of people with MS.
The dissonance observed in physical activity measurement and qualitative description of physical activity could have occurred for several reasons. Although there is evidence that the GLTEQ provides a valid measure of physical activity in people with MS,38–40 it is a crude, noncomprehensive measure of physical activity; it does not capture household, occupational, or transportation activities, which may dominate some participants’ activity The magnitude of correlation between fatigue and the subjective measures may have been influenced by the truncated range of scores, as the sample was characterized by a low level of physical activity. Further examination of the context in which physical activity was discussed revealed that the discrepancy could be because physical activity was described acutely in interviews, whereas the psychometric data were collected in the context of long duration. Differences seen between quantitative and qualitative data surrounding fatigue and physical activity could originate from acute effects of body sensations and emotions experienced with fatigue on physical activity. These acute effects could be greater or more salient than the cumulative effects of these variables on the behavior, the memory of which may attenuate over time. Some qualitative evidence suggests that people with MS feel the need to conserve energy and plan day-to-day activities around fatigue36; this evidence is corroborated by discussion of energy planning in this sample. Further studies should examine the potential impact of fatigue experiences, including body sensations and emotions felt during fatigue, on both short- and long-term physical activity.
Qualitative discussions of the emotions accompanying fatigue indicate that this sample tended to respond to fatigue with anger or frustration. This is corroborated quantitatively by a low mean ESS score, which indicates that this sample is not likely to feel helplessness, discomfort, inadequacy, or vulnerability in response to a threatening stimulus such as fatigue.17 Other qualitative research regarding the fatigue experience in people with MS does indicate anger associated with fatigue, particularly around the inability to complete tasks when fatigued.36, 41
Limitations
This study has limitations that affect the results. This study would have benefited from a control sample of quantitative data for comparison and a larger sample. The participants were overwhelmingly female by a higher percentage than the existing population41 and mostly White, although MS affects all races.42 Because participants were asked to identify themselves as “active” as a screening criterion for physical activity level, the sample obtained could have been biased. People with MS who do not consider themselves active could approach and respond to fatigue in a different way. Investigating these constructs further in a more diverse sample is warranted.
The MAIA-2 and ESS have not been widely used in samples of people with MS, resulting in an absence of psychometric evidence regarding the reliability and validity of these scores for people with MS. Evidence from other groups supports the validity of these scales, including those with eating disorders, depression, and pain,43–45 but the interpretability of the quantitative results are less certain than if supportive psychometric data were available from a large sample of people with MS.
Measures that plausibly could have helped explain the results or put them into a broader context within the literature were not included in this study. For example, widely used personality traits, such as those in the Big Five model of personality, were not measured herein, although these personality traits have demonstrable relationships to all the outcomes measured. For example, the trait of neuroticism has been shown to be significantly related to fatigue,46 interoceptive awareness,47 and emotional susceptibility.48 Future research examining the outcomes used in the present study may benefit by including measures of personality traits or other assessments (eg, biomarkers of fatigue, symptoms of depression, sleep) that may help explain the relationships.
Finally, these data were collected during the COVID-19 pandemic, which could have affected the level of fatigue experienced by this sample as well as the emotions experienced during this time.
Conclusions
This study provides a novel, comprehensive view of the experience of fatigue for people with MS and provides useful information for clinicians. The experience of fatigue is common, strong, and multifaceted, with substantial implications for daily function and quality of life as well as differential diagnosis. Traditional methods of fatigue measurement (eg, questionnaires) may not elucidate the full experience, so practitioners should consider asking more in-depth questions regarding the ways fatigue manifests itself physically and emotionally, particularly when planning physical activity. Patients who report more of the cognitive aspects of fatigue may need simpler and clearer directions from a therapist. Alternatively, those who experience stronger emotional aspects of fatigue may benefit from more obvious emotional support as part of the therapy process.
