AbstractsPsychology

Various aspects of fatigue in multiple sclerosis (MS) are explained in the literature, however, there is inconsistent evidence regarding daily variation of fatigue and its association with physical activity. While there is evidence from randomized controlled trials (RCT) that exercise can reduce fatigue, the relationship between these variables is a "chicken or egg" phenomenon, and is not clear whether fatigue is a cause or consequence of physical inactivity.The global aim of this study is to contribute evidence towards the daily variability in fatigue and to delineate the temporal sequence between fatigue and physical activity in people with MS.This is a longitudinal predictive study over two time periods embedded in an RCT on exercise for MS (MSTEP). Fatigue was measured using 10 point visual analogue scale for 4 time points every day. Physical activity was recorded on accelerometer for two contiguous periods of 7 days, one period immediately after trial entry and assessment, and one period after the first exercise prescription, for maximum data points of 56 per person. Data was analyzed using Generalized Estimating Equations to adjust the variance for the clustering of measures within person. Odds ratio (OR) was used to identify peak times of the day for fatigue.The results on 40 participants suggested that the odds of having maximum fatigue increased along the course of the day (lowest in morning, highest at night). Compared to 8:00 hours, the OR associated with having maximum fatigue at 16:00 hours was 2.56 (95% CI: +0.21, +1.67); and at 21:00 hours was 4.84 (95% CI: +0.88, +2.27). At neither time period did end-of-day fatigue level impact on next day physical activity as measured by number of steps and the same null effect was observed between physical activity throughout the day and fatigue the next day. In this sample of people with MS participating in an exercise trial, there was no evidence linking fatigue and physical activity, potentially breaking the myth that physical activity increases fatigue. This should be reassuring to people with MS who wish to increase physical activity but fear negative impacts on fatigue. Divers aspects de la fatigue reliés à la sclérose en plaque (SP) sont expliqués dans la littérature. Cependant, les évidences sont inconsistantes concernant la variation quotidienne de la fatigue et son association avec l'activité physique. Bien qu'il y ait des évidences provenant d'essais randomisés contrôlés (ECR) démontrant que l'exercice peut réduire la fatigue, la relation entre ces variables est un phénomène de «l'œuf ou la poule» et il n'est pas clair sir la fatigue st une cause ou une conséquence de l'inactivité physique.L'objectif global de cette étude est de contribuer à l'avancement des évidences concernant la variabilité de la fatigue et de délimiter la séquence temporelle entre la fatigue et l'activité physique chez les personnes atteintes de SP.Il s'agit d'une étude longitudinale, réalisée sur deux périodes de temps et intégrée dans un ECR, sur liens prédictifs de…