According to the evidence, between 11 percent and 30 percent of people who develop a blood clot in the legs, known as a deep vein thrombosis or DVT, or a blood clot in the lungs, known as a pulmonary embolism, or PE, die within 30 days of their diagnosis.
Researchers tracked the health of most of the population of Taiwan (23.74 million people) through the country's compulsory national insurance scheme between 1998 to 2008, and included a further monitoring period up to the end of 2010, to find out if rheumatoid arthritis raised the risk of potentially fatal blood clots.
Just less than 30,000 people developed rheumatoid arthritis during this period, and their details were entered into a national (catastrophic illness) registry of the National Health Insurance Database (NHIRD). By way of comparison, they were matched with almost 117,000 healthy people of the same age and sex.
Patients with rheumatoid arthritis were more likely to have other underlying conditions, like high blood pressure, diabetes, high cholesterol, heart failure and fractures, than were those in the comparison group.
But even after taking account of these influential factors, and allowing for age, patients with rheumatoid arthritis were still significantly more likely to develop potentially fatal blood clots, the analysis revealed.
They were more than three times as likely to develop a DVT, and twice as likely to develop a PE as those without the condition, the figures showed.
Furthermore, rheumatoid arthritis packed the greatest punch in the under 50s, who were almost six times as likely to develop a DVT and more than three times as likely to develop PE than were either middle aged (50 to 65) or older adults.
The findings of the study have been published online in the Annals of the Rheumatic Diseases.