Fatigue in MS - things you should know

J Behav Med. 2017 Mar 9. doi: 10.1007/s10865-017-9840-4. [Epub ahead of print]

Tracking daily fatigue fluctuations in multiple sclerosis: ecological momentary assessment provides unique insights.

Powell DJ, Liossi C, Schlotz W, Moss-Morris R.


Studies investigating the prevalence, cause, and consequence of multiple sclerosis (MS) fatigue typically use single measures that implicitly assume symptom-stability over time, neglecting information about if, when, and why severity fluctuates. We aimed to examine the extent of moment-to-moment and day-to-day variability in fatigue in relapsing-remitting MS and healthy individuals, and identify daily life determinants of fluctuations. Over 4 weekdays, 76 participants (38 relapsing-remitting MS; 38 controls) recruited from multiple sites provided real-time self-reports six times daily (n = 1661 observations analyzed) measuring fatigue severity, stressors, mood, and physical exertion, and daily self-reports of sleep quality. Fatigue fluctuations were evident in both groups. Fatigue was highest in relapsing-remitting MS, typically peaking in late-afternoon. In controls, fatigue started lower and increased steadily until bedtime. Real-time stressors and negative mood were associated with increased fatigue, and positive mood with decreased fatigue in both groups. Increased fatigue was related to physical exertion in relapsing-remitting MS, and poorer sleep quality in controls. In relapsing-remitting MS, fatigue fluctuates substantially over time. Many daily life determinants of fluctuations are similar in relapsing-remitting MS and healthy individuals (stressors, mood) but physical exertion seems more relevant in relapsing-remitting MS and sleep quality most relevant in healthy individuals.

Figure 1: Average fatigue trajectories over time in the relapsing-remitting MS group (red solid line) and the control group (green dashed line).

Last week I posted on memory and intelligence in MS, and this week I'll be looking at fatigue. Fatigue is not a tangible symptom, sometimes it is difficult to pin point when it all started and you loose sight of (over time) of when it will end. However, the accepted definition of fatigue in MS is: "a subjective lack of physical and/or mental energy that is perceived by the individual or caregiver to interfere with usual and desired activities” (Multiple Sclerosis Council for Clinical Practice Guidelines, 1998).

To my knowledge this is the first study looking at the diurnal (during the day) variation in fatigue. Powell et al. report that on balance in relapsing-remitting MS compared to controls, there was a quicker increase in severity earlier on, peaking in late-afternoon; Figure 1 (although this was not the case in everyone). In those without MS, there was steady increase in fatigue throughout the day. Real-time fatigue increased with a negative mood, or decreased positive mood. Specifically, being discontent at work and lack of social recognition - that is increased exposure to stressors, worsened fatigue.  Interestingly, they also noted that physical activity in the last 30min lead to increased fatigue, reminiscent of post-exertional fatigue reported in chronic fatigue syndrome. Of note, the exertion question was a binary one (yes/no), and there is no detail on the intensity of the activity, so not sure what this means in real-life terms. You only have to speak to a runner (MS and non-MS alike), who chase their next endorphin hit that this is a complicated one to answer. Something more easier to understand is that in those without MS, lack of sleep is a big culprit.

The findings of this work are not to be taken as gospel, but simply a point of reference. I grew up believing that rules existed to be defied; often eschewing the traditional approach for the less conventional approach (MD has alluded to this in the past over my rock climbing antics!). But I tell you, happiness can define more than a moment of your life, it also allows you to see those moments with greater clarity.

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