Pain, Fatigue, and Cognitive Symptoms Are Temporally Associated Within but Not Across Days in Multiple Sclerosis

Objective: To examine the temporal associations, within day and day to day, between pain, fatigue, depressed mood, and cognitive function in multiple sclerosis (MS).

Design: Repeated-measures study involving 7 days of ecological momentary assessment (EMA) of symptoms 5 times a day; multilevel mixed models were used to analyze data.

Setting: Community.

Participants: Ambulatory adults (N=107) with MS.

Interventions: Not applicable.

Main outcome measure: EMA of pain, fatigue, depressed mood, and cognitive function rated on a 0 to 10 scale.

Results: Fatigue and pain were linked within day such that higher pain was associated with higher subsequent fatigue (B=.09, P=.04); likewise, higher fatigue was associated with higher pain in the following time frame (B=.05, P=.04). Poorer perceived cognitive function preceded increased subsequent pain (B=.08, P=.007) and fatigue (B=.10, P=.01) within day. Depressed mood was not temporally linked with other symptoms. In terms of day-to-day effects, a day of higher fatigue related to decreased next day fatigue (B=-.16, P=.01), and a day of higher depressed mood related to increased depressed mood the next day (B=.17, P=.01). There were no cross-symptom associations from one day to the next.

Conclusions: Findings provide new insights on how common symptoms in MS relate to each other and vary within and over days. Pain and fatigue show evidence of a dynamic bidirectional relation over the course of a day, and worsening of perceived cognitive function preceded worsening of both pain and fatigue. Most temporal associations between symptoms occur within the course of a day, with relatively little carryover from one day to the next.