Rheumatoid arthritis (RA) patients who had the disease's symptoms in winter or in spring have more severe outcomes at six months, than those whose symptoms first appeared in summer, says study.
The researchers measure the severity of RA by the modified Total Sharp Score, mTSS, an assessment of erosion and joint space narrowing.
In addition, the patients' mTSS after six months showed poorer radiographic outcome if their first symptoms had occurred in winter versus autumn as the reference season.
However, the effect was not observed at 12 month follow up, which, according to the authors, could suggest that these initial environmental factors exert less of an effect on longer term radiographic progression.
"During our study of predictors of radiographic progression, we have unveiled a distinct relationship between RA progression and seasonal onset and postulate that this could be as a result of either a vitamin D deficiency or environmental factors, such as winter viruses, influencing protein citrullination. Anti-citrullinated protein antibodies (ACPAs) are often found in the immune systems of RA patients.
This finding may assist towards the identification of RA patients at a higher risk of developing structural damage, in order to propose early intensive therapy and minimise disease progression," said Dr. Gael Mouterde, who led the research.
The study was conducted on 736 patients from the multicentre French ESPOIR cohort.
It was presented at EULAR 2009, the Annual Congress of the European League Against Rheumatism in Copenhagen, Denmark.