It’s well established that inflammatory types of arthritis, like rheumatoid arthritis, or RA, are associated with an increased risk of cardiovascular disease. Now, a Dutch study shows that if in addition to the arthritis you have hypothyroidism – a condition in which the thyroid gland produces an insufficient amount of hormones – your risk is even higher.

“Evidence is accumulating,” explains study co-author Michael T. Nurmohamed, MD, PhD, a rheumatologist at VU University Medical Center in Amsterdam. “Rheumatoid arthritis as well as hypothyroidism are independently associated with an increased cardiovascular risk, such as heart attacks and strokes. If you have both, then the risk is amplified,” he says. The study was published online March, 2012, in Annals of the Rheumatic Diseases.

For the study, the researchers collected information from a primary care database on more than 175,000 Dutch patients older than 30. They used diagnosis codes to identify patients with inflammatory types of arthritis – defined in this study as RA and ankylosing spondylitis, a type of arthritis that primarily affects the spine and pelvis – as well as those with hypothyroidism and cardiovascular disease, or CVD, including heart attack and stroke.

More than 1,500 patients were found to have inflammatory arthritis. Both male and female patients with inflammatory arthritis had higher rates of hypothyroidism than those without inflammatory arthritis – 6.5 percent vs. 3.9 percent among women, and 2.4 percent vs. 0.8 percent among men. 

After adjusting for risk factors including age, hypertension, cholesterol levels and the presence of diabetes, researchers found female patients with both inflammatory arthritis and hypothyroidism had a 3.7 times higher prevalence of cardiovascular disease than the control group (people without either condition). Female patients with only inflammatory arthritis had a 1.5 higher prevalence of CVD compared to controls and those with hypothyroidism had a 1.2 percent higher prevalence of CVD. There weren’t enough male patients with both conditions to conduct a meaningful analysis.

Dr. Nurmohamed and his colleagues write that a link between inflammatory arthritis and hypothyroidism has long been suspected, but evidence scientifically supporting the association was lacking. Inflammatory types of arthritis are autoimmune disorders, in which the body attacks itself. The most common cause of hypothyroidism is another autoimmune disorder, called Hashimoto’s disease, in which the body attacks its own thyroid gland.