Epub ahead of print: Feys et al. Effect of time of day on walking capacity and self-reported fatigue in persons with multiple sclerosis: a multi-center trial. Mult Scler. 2011 Oct 3.
Background: Many MS'ers 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 study was to determine whether self-reported fatigue level and walking capacity are influenced by time of day in PwMS.
Methods: A total of 102 MS'ers with a diverse level of ambulatory dysfunction participated. MS'ers 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 but reported similar fatigue levels. Although RFD scores were affected by time of day with significant differences between morning and noon/afternoon, 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.
"One finding in this study doesn't fit well with my clinical experience. Most MS'ers, with lower limb weakness and spasticity, find that their walking ability drops off during the day particularly if they exercise."
"Worsening mental fatigue, or the perception of worsening physical fatigue, with time is often reported by MS'ers, which is why we typically recommend delaying the use of anti-fatigue medication (amantadine) until the late morning or early afternoon."
"Pleases note that perceived fatigue levels do not correlate with physical disability as measured by the EDSS. This is a finding that has been reproduced many times. People, in particular employers, find this difficult as MS'ers may have very little or no physical disability and can still be incapacitated by fatigue."
"People expect MS-related fatigue to be related to physical disability, but it is not."
"I have always felt that there must be an area of the brain that perceives fatigue. If we can find that area we may be able to block its activity by using a neurostimulator. In other words if we cab switch off that part of the brain we could block the subjective experience of fatigue. This form of treatment may help treat MS'ers, and other patients, incapacitated with fatigue. As these neurostimulator devices are widely available to treat other neurological disorders this treatment could be translated very quickly. The problem is we have yet to identify the area of the brain that perceives fatigue."
"Please remember fatigue is a normal part of our behaviour; we get tired so that we can rest and recover, and in the case of the brain consolidate memories. So this type of treatment would need to be intermittent and allow periods of recovery and consolidation."
"Science Fiction? May be not."