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05-11-2018 | Rheumatoid arthritis | News

Elevated autoimmune thyroid disease risk in RA patients declines over time


medwireNews: Study findings suggest that patients with rheumatoid arthritis (RA) have an increased risk for autoimmune thyroid disease (AITD) relative to the general population in the period leading up to arthritis diagnosis, but the risk reduces after this time.

Previous research has demonstrated “an increased prevalence of RA among patients with AITD, an increased prevalence of AITD among patients with RA, or an increased prevalence of thyroid autoantibodies in patients with RA,” but little is known about “the risk of developing these conditions over time,” write the study authors in JAMA Network Open.

Using data from Swedish national registries, Kristin Waldenlind (Karolinska Institutet, Stockholm, Sweden) and colleagues demonstrated that 10.3% of 8090 patients with RA had AITD at the time of RA diagnosis, compared with 7.1% of 80,782 population controls, translating into a significant odds ratio (OR) of 1.5.

The risk for AITD among RA patients relative to controls was highest during the period up to 3 months prior to RA diagnosis (OR=5.3), and was still significantly elevated, but to a lesser degree, in the periods from 3 months to less than a year (OR=2.0), 1 to less than 2 years (OR=1.4), and 2 to less than 5 years prior to RA diagnosis (OR=1.5). However, RA patients did not have an elevated risk for AITD more than 5 years before their diagnosis of RA.

In the period after RA diagnosis, AITD risk remained significantly elevated among RA patients relative to the general population for up to 3 months (OR=2.1), but leveled off after this timepoint, and RA patients had a nonsignificant decrease in AITD risk around 2 years and onwards after RA diagnosis.

“The results of this study extend previous findings of an increased occurrence of AITD among patients with RA by demonstrating that much of the increased risk of AITD by the time of diagnosis of RA develops during the last few years before diagnosis and that, thereafter, the incidence of AITD is no longer elevated but decreased,” say Waldenlind and team.

They say that their findings “highlight that patients with AITD who have joint symptoms should be evaluated for a potential new-onset RA,” whereas “patients with RA may be reassured that their risk of also developing AITD is not increased.”

And the researchers conclude: “Why the risk of developing AITD seems to decrease after diagnosis of RA and whether this decrease in risk represents a protective effect of immunomodulatory therapies need to be further investigated.”

By Claire Barnard

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