Swedish researchers have found an increased risk of venous thromboembolism – blood clots in the veins – in people with rheumatoid arthritis beginning at diagnosis and persisting for at least 10 years.

Venous thromboembolism, or VTE, is a disease that includes both deep vein thrombosis and pulmonary embolism. Deep vein thrombosis, or DVT, is a blood clot that forms in one of the deep veins within the body, usually in the leg, blocking blood flow to the area and causing pain, redness and swelling. Pulmonary embolism, a life-threatening condition, occurs when a clot (usually from a DVT) breaks away and travels to the lungs, blocking blood flow and causing shortness of breath, pain and cough.

The new study, which appears in the October 3, 2012 issue of the Journal of the American Medical Association, compared more than 45,000 Swedes with rheumatoid arthritis, or RA, with members of the general population. The researchers found that among those with “prevalent” – or established – RA, the incidence of venous thromboembolism was twice that of the general population (2.2 percent vs. 1.1 percent over the 13-year study period).

But there is a bit of good news in the study for those with RA, says study co-author Marie Holmqvist, MD, PhD, a research fellow in the clinical epidemiology unit at the Karolinska Institute in Stockholm. Hospitalization – a traditional risk factor for serious blood clots, especially among people with autoimmune diseases such as RA – doesn’t further increase the risk. “These findings in combination are important,” Dr. Holmqvist says. “Because this means that although RA patients in general are at increased risk, there is no reason to fear that they are at extra high risk in conjunction with hospitalization, which has been suggested previously.”