Annual fluctuations in rheumatoid arthritis.

A literature survey revealed many reports implicating the microclimate and seasonal changes in arthritic diseases. Therefore, a retrospective study of the erythrocyte sedimentation rate (ESR) and the C-reactive protein (CRP) concentration of 2,802 rheumatoid arthritis (RA) was performed. No statistically significant fluctuation was found when analyzed according to the month of the year in which blood was taken. The significance of this is discussed in relation to other RA symptoms, meteorologic phenomena, microclimate, and the joint circulatory responses in RA. The observations reported are consistent with the concept that seasons and microclimate may affect some of the symptoms of RA, but not the inflammatory processes represented by the ESR and CRP.