Seasonal variations in fatigue in persons with rheumatoid arthritis: a longitudinal study.

BACKGROUND Fatigue is a prominent symptom in persons with rheumatoid arthritis (RA). Although this symptom has been described to vary in duration and frequency little is known about fluctuations in fatigue over time and season. The aim of this study was to describe monthly and seasonal variations in fatigue, in persons with RA of working age. METHODS Sixty-five participants diagnosed with RA and aged 20-65 years were recruited from a rheumatology clinic in Sweden. The participants provided self-assessments of their fatigue at seven time points during the four seasons using a 0-100 mm visual analogue scale (VAS) and the Bristol Rheumatoid Arthritis Fatigue Multidimensional Questionnaire (BRAF-MDQ). Multiple regression analysis using mixed models was used to analyze changes in fatigue over time. RESULTS The mean ± SD of fatigue rated on the VAS was 51 ± 13, indicating substantial fatigue. Analysis of monthly variation showed statistically significant variation in fatigue ratings concerning VAS fatigue score (p < 0.01) as well as the BRAF-MDQ total score and Living, Cognition (p < 0.001), and Physical (p < 0.05) sub-scores, but not the BRAF-MDQ Emotional sub-score. The greatest variations were seen from January to September, with higher fatigue ratings in January. The changes in VAS fatigue scores over time were considered to be of clinical importance. Analysis of seasonal variation revealed a statistically significant seasonal variation in fatigue levels, with higher fatigue values during the winter as measured by VAS fatigue score (p < 0.01) as well as BRAF-MDQ total score (p < 0.01) and Physical and Living sub-scores (both p < 0.01). The greatest variation was seen between winter and autumn for VAS fatigue and between winter and summer for BRAF-MDQ total score and Physical and Living sub-scores. There were no statistical differences in fatigue levels, monthly or seasonal, between sexes or age groups. CONCLUSIONS The majority of rating scales used in this study showed fluctuations in fatigue, general and physical fatigue being significantly greater during the winter. As fatigue is a substantial symptom in many persons with RA, this information is important for rheumatology professionals when dealing with persons with RA in routine care.