Pain, Fatigue, and Cognitive Symptoms Are Temporally Associated Within but Not Across Days in Multiple Sclerosis.
Anna L Kratz, Susan L Murphy, Tiffany J Braley
PMID 28729169WHAT IT FOUND
In adults with MS, pain, fatigue, and self-reported thinking problems were linked from one rating to the next within the same day.
Fatigue rose toward bedtime, but one day's symptoms did not predict a different symptom the next day. No treatment was tested.
Key findings
01Within the same day, higher previous fatigue and worse previous thinking were followed by higher pain, and higher previous pain and worse previous thinking were followed by higher fatigue.
02From one day to the next, no symptom predicted a different symptom; higher fatigue one day was followed by lower fatigue the next, while higher depressed mood was followed by higher depressed mood.
03Depressed mood was linked only to its own earlier rating, not to later pain or fatigue, and cognitive function was mostly linked only to its own earlier rating.
STILL TO COME
How it was doneWhat they foundWhat it means for PTs
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What it does not show
Only ambulatory people with mild symptoms were included, so findings may not apply to people with more severe MS. Most participants were white and female, which limits generalizability to other groups. Data came from seven days only, and 83.4% of possible momentary ratings were complete. The study was observational, so it cannot show that one symptom causes another. The momentary cross-symptom links were small in absolute terms. The analysis used separate models and assumed equal time intervals between ratings. Survey ratings and momentary ratings differed in ways the authors did not explain. The symptoms were chosen because they respond to behavioral intervention, so other important MS symptoms were not examined.
Declared interests
The authors declared no conflicts of interest. The publication types list NIH extramural research support.
The easy way to misread this
Do not conclude that treating pain will reduce fatigue or that one day's symptom level predicts a different symptom the next. This was an observational seven-day study, and the associations were within-day, not causal.