FRIDAY, Nov. 25, 2011 (HealthDay News) -- Patients hospitalized for autoimmune disorders, like rheumatoid arthritis or Crohn's disease, may be at greater risk for a life-threatening pulmonary embolism, a clot in a main artery of the lung, a new study finds.
Reporting online Nov. 25 in The Lancet, researchers warned that steps should be taken to prevent this condition among patients admitted to the hospital for autoimmune diseases.
In conducting the study, researchers analyzed data on more than 500,000 patients admitted to the hospital in Sweden for one of 33 autoimmune diseases, which can also include Grave's disease, Hashimoto's thyroiditis and chronic rheumatic heart disease.
The team, led by Dr. Bengt Zoller of Malmo University Hospital in Sweden, found the overall risk of pulmonary embolism in the 12 months following hospitalization to be six times higher for patients with autoimmune diseases than for those without this type of disorder.
They noted that all of the 33 autoimmune disorders included in the study were associated with a significantly higher risk of pulmonary embolism, although the most notable increases were associated with immune thrombocytopenic purpura, a clotting disorder, which carried an 11-fold increased risk; polyarteritis nodosa, a form of vasculitis (13 times the risk); and polymyositis, which involves chronic muscle inflammation (16 times the risk).
The rise in risk did decrease over time, however. Between one and five years after hospitalization, overall risk dropped to a 50 percent increased risk for those with autoimmune disorders, the researchers found. The risk dropped even further, to 15 percent five to 10 years after admission, and fell to just 4 percent after 10 years or more.
The researchers pointed out the risks were the same for men and women, and did not vary across age groups.
Zoller and colleagues said in a journal press release that preventive measures against pulmonary embolism "could be warranted in patients admitted with autoimmune disorders or at least for those disorders for which the risk of pulmonary embolism was very high. Further studies are needed to assess the potential usefulness of such treatment."
In a journal commentary, Dr. Carani B Sanjeevi, of the Karolinska Institute and Karolinska University Hospital in Stockholm, said that a "clear link is shown between thrombosis and inflammation" in the study. She agreed that "anti-inflammatory drugs and thromboprophylaxis [prevention of clots] should be considered to treat inflammation associated with autoimmune disorders, particularly in those admitted to hospital."
Sanjeevi added that more research is needed to investigate the link between inflammation and pulmonary embolism.
The U.S. National Institutes of Health provides more information on autoimmune diseases.