Background Experimental data suggest shared susceptibilities but also an “either or” pattern of risk for RA and multiple sclerosis (MS). Observational data have suggested a possible reduced occurrence of MS among patients with RA . Other reports have suggested a possible increase in the occurrence of demyelinating events in RA treated with TNF inhibitors . A proper understanding of the co-occurrence of RA and MS is thus both of etiological and clinical importance.
Objectives Our aim was to estimate the risk of RA among patients who had had a demyelinating event and/or MS, and the risk of MS/demyelinating events in patients with prior RA diagnosis, compared to the general population.
Methods Cases with incident RA were identified from the national patient register (NPR; Swedish inpatient and outpatient care) and the Swedish Rheumatology Quality Register (SRQ). General population comparators were selected from the Swedish population register matched to the RA patients by age, sex and county. Data on demyelinating disease and MS among RA patients and their population comparators were extracted from the NPR. We used logistic regression models to calculate the odds ratio (OR) of having a history of MS by the time of RA diagnosis, and Cox regression models to calculate the hazard ratio (HR) of MS following RA diagnosis, in both analyses compared to the general population.
Results We included 8,170 incident RA cases from SRQ and 40,728 general population matched controls. The OR for RA associated with a history of MS was 0.68 (95%CI; 0.38, 1.21) and the OR for RA associated with a history of a demyelinating event was 0.48 (95%CI; 0.17, 1.32). Counting from RA diagnosis and onwards, we observed only 1 MS case in the RA population and 24 MS cases among the population comparators, corresponding to a HR=0.26 (95%CI 0.04, 1.97). RA was associated with an increased risk of subsequent demyelinating event (HR 2.59 95%CI 1.24, 5.39). When the same analyses were performed using RA identified in the Patient Register, numbers increased but all associations remained of similar strength.
Conclusions The risk of RA among patients with a history of MS was reduced by a third. Cases of MS after RA onset were rare, suggesting shared but opposing or exclusive susceptibilities of the two diseases. By contrast, the risk for demyelinating events was reduced before RA onset, but not thereafter, indicating a cause-and-effect association with the RA disease.
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Seror R, Richez C, Sordet C, et al. Pattern of demyelination occurring during anti-TNF-alpha therapy: a French national survey. Rheumatology (Oxford) 2013;52:868-74.
Disclosure of Interest None declared
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