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Season-associated environmental factors have been related to the onset of rheumatoid arthritis (RA) and the severity of joint complaints.1 ,2 A recent study demonstrated that the onset of arthritis symptoms during winter or spring was associated with more radiographic joint damage after 1 year.3 This led us to evaluate the influence of the season of symptom onset on long-term radiographic progression.
Six hundred and eighty-eight RA-patients, from the Leiden Early Arthritis Clinic (EAC) and 830 RA-patients from the Swedish BARFOT-study were included in the study.4 ,5 These cohorts were similar in the percentage of women patients, age, symptom duration, swollen joint count, C reactive protein and the percentage of anti-cyclic citrullinated protein antibody positive patients (data not shown). During a follow-up period of 5 and 7 years, a total of 6990 hands and feet x-ray sets were obtained and scored for joint damage according to the Sharp-van-der-Heijde method ( all …
Contributors AvdHM, TWJH and BS collected the data. DPCdR, BS and MLEA performed the statistical analyses. DPCdR wrote the first version of the manuscript. All authors reviewed and approved the manuscript.
Competing interests None.
Ethics approval This study was approved by the local medical ethics committees of both cohorts (Leiden EAC and BARFOT).
Provenance and peer review Not commissioned; externally peer reviewed.
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