Their findings were reported in "Hypothyroidism as a risk factor for the development of cardiovascular disease in patients with rheumatoid arthritis", which was published in the Journal of Rheumatology.
The research team conducted a retrospective medical record review. They used all incident cases of adult-onset RA from Olmsted County, MN, between 1988 and 2007.
To see if CVD developed in these patients—some had thyroid disease while others did not—they were followed longitudinally.
The study included two groups. One group consisted of 650 patients who had RA, and the other group was an age- and sex-matched comparison cohort that included 650 patients who did not have RA. The mean age for both groups was 55.8 years old, and 69% were women.
The researchers found that at the time the patients were diagnosed with RA, there was no significant difference between the groups in the presence of hypothyroidism or subclinical hypothyroidism. Additionally, they found that there was no significant difference in the cumulative incidence of hypothyroidism between the 2 groups.
However, researchers found that there was a significant relationship between hypothyroidism and CVD in patients who have RA (hazard ratio: 2.0; 95% confidence interval [CI]: 1.1, 3.6). They noted that this difference remained both significant and unchanged after adjusting for other traditional cardiovascular risk factors (hazard ratio: 2.0; 95% CI: 1.1, 3.6).
The research team concluded that although there was no significant difference in either incidence or prevalence of hypothyroidism in patients with or without rheumatoid arthritis, hypothyroidism was significantly linked to cardiovascular disease in patients with RA.