Effect of time of day on walking capacity and self-reported fatigue in persons with multiple sclerosis: a multi-center trial.
BACKGROUND
Many persons with multiple sclerosis (PwMS) report increased fatigue in the afternoon and evening compared with the morning. It is commonly accepted that physical capacity also decreases as time of day progresses, potentially influencing the outcomes of testing.


OBJECTIVE
The objective of this article was to determine whether self-reported fatigue level and walking capacity are influenced by time of day in PwMS.


METHODS
A total of 102 PwMS from 8 centers in 5 countries, with a diverse level of ambulatory dysfunction (Expanded Disability Status Scale [EDSS] <6.5), participated. Patients performed walking capacity tests and reported fatigue level at three different time points (morning, noon, afternoon) during 1 day. Walking capacity was measured with the 6-Minute Walk Test (6MWT) and the 10-m walk test performed at usual and fastest speed. Self-reported fatigue was measured by the Rochester Fatigue Diary (RFD). Subgroups with mild (EDSS 1.5-4.0, n = 53) and moderate (EDSS 4.5-6.5, n = 49) ambulatory dysfunction were formed, as changes during the day were hypothesized to depend on disability status.


RESULTS
Subgroups had different degree of ambulatory dysfunction (p < 0.001) but reported similar fatigue levels. Although RFD scores were affected by time of day with significant differences between morning and noon/afternoon (p < 0.0001), no changes in walking capacity were found in any subgroup. Additional analyses on subgroups distinguished by diurnal change in self-reported fatigue failed to reveal analogous changes in walking capacity.


CONCLUSIONS
Testing of walking capacity is unaffected by time of day, despite changes in subjective fatigue.