Hospital patients admitted for autoimmune disorders, such as rheumatoid arthritis, have a higher risk of pulmonary embolism than other people, according to Swedish researchers from Lund University.
They compared pulmonary embolism risk in 535,000 patients admitted for autoimmune diseases with the rest of the population.
They found 31 of the 33 diseases studied were linked with increased clot risk after discharge, which was particularly high in the first year.
Lead author associate professor Bengt Zöller said: “The risk was particularly high in the first year - around six times higher on average in all the groups with autoimmune diseases compared with the control group. For some of the diseases, the risk was even higher in the first year.”
The diseases that stand out were idiopathic thrombocytopenic purpura, systemic lupus erythematosus, polymyositis, dermatomyositis and polyarteritis nodosa, all of which had at least a tenfold risk increase.
Rheumatoid arthritis was associated with a sevenfold increase in the risk and type 1 diabetes a sixfold increase in the risk during the first year, following hospital treatment.
Dr Zöller said: “The risk of a blood clot fell with time. It was still around 50% higher after one to five years, yet there remained an increased risk for up to ten years after the first admission to hospital for many autoimmune conditions.”
Patients who have been admitted to hospital for autoimmune diseases require preventive treatment for blood clots in the same way as following major surgery, the authors suggest online in The Lancet.