To examine whether a seasonal fluctuation exists with rheumatoid arthritis (RA) activity and to analyse seasonal effects of varying components that express disease activity in RA patients.
A group of 1665 RA patients (mean age 57.2 yrs, mean disease duration 9.9 yrs) whose data were available for 10 consecutive phases from a large observational cohort study conducted at our institution from October 2000 to April 2005, bi-annually, were evaluated. Ten criteria were analysed to assess RA disease activity.
All criteria revealed decrease in disease activity during fall and increase in disease activity during spring, except for the physician's global assessment of disease activity in which significant differences were not observed between the two seasons.
We found definite seasonal differences in RA patients, both subjectively and objectively. RA disease activity was higher in spring and lower during fall. Seasonal changes may play an important role in evaluating disease activity of RA patients and should be taken into account when examining these patients.