There is increased prevalence of autoimmune thyroid disease among patients with rheumatoid arthritis (RA) during the 5 years before diagnosis of RA, peaking around time of diagnosis and decreasing 2 to 5 years after diagnosis, according to study results published in JAMA Network Open.
Researchers in this register-based, case-control and cohort study used data collected between January 2006 and June 2013 to estimate the risk for thyroxine-treated autoimmune thyroid disease (including hyperthyroidism and hypothyroidism) among patients with RA at various time points before, at, and after diagnosis. They used data from the Swedish Rheumatology Quality Register to identify 8090 adults diagnosed with new-onset RA, as well as 10 reference participants individually matched for sex, age, and residential area for each patient with RA (n = 80,782).
Of 8090 patients with RA (2561 men, 5529 women; mean age, 58.3 years), 10.3% (n = 832) had autoimmune thyroid disease by the time they were diagnosed with RA, compared with a 7.1% (5725 of 80,350) prevalence among the control group participants (odds ratio [OR], 1.5; 95% CI, 1.4-1.7). This increased risk for thyroid disease developed in the 2 to 5 years before diagnosis (OR, 1.5; 95% CI, 1.2-1.8), peaked at 0 to 3 months before RA diagnosis (OR, 5.3; 95% CI, 3.7-7.6), and then decreased in the 2 to 5 years following diagnosis (hazard ratio, 0.7; 95% CI, 0.5-1.0).
Study investigators concluded that “the risk [for autoimmune thyroid disease] varied between its subsets, hypothyroidism and hyperthyroidism, and with age, sex, and RA subgroup, but the temporal pattern of risk was similar across the patient subgroups. Why the risk… 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.”
Waldenlind K, Saevarsdottir S, Bengtsson C, Askling J. Risk of thyroxine-treated autoimmune thyroid disease associated with disease onset in patients with rheumatoid arthritis. JAMA Netw Open. 2018;1(6):e183567.