A large Swedish study has found a link between gastrointestinal or urinary tract infections and a significantly lower risk of developing rheumatoid arthritis. But respiratory infections were not associated with lower risk. This may mean that changes in the types or amounts of bacteria in the intestinal system might reduce the risk of rheumatoid arthritis.
Other research has found a connection between infection and rheumatoid arthritis, which is an autoimmune disease, but this is the first study of whether specific types of infection or locations are connected.
Researchers matched 2,831 Swedes with rheumatoid arthritis to 3,570 healthy Swedes. They were enrolled in the study between 1996 and 2009, when the people with arthritis were newly diagnosed. All of them were asked if they had any gastrointestinal, urinary, genital, or prostate infections, or had been treated with antibiotics for sinusitis, tonsillitis or other throat infection, or pneumonia in the two years preceding entering the study.
People who said they had a gastrointestinal, urinary tract, or genital infection within the preceding two years had a significantly lower risk of developing rheumatoid arthritis. The risk was lowered by 29% for a gastrointestinal infection, 22% for a urinary tract infection, and 20% for a genital infection. Having had all three types of infection in the preceding two years was linked to a 50% lower risk. No such lowering of risk was associated with recent respiratory infections and pneumonia, nor was there lowering when the infections occurred sooner than a year earlier.
The lowered risk of rheumatoid arthritis was associated with these infections, but there is no way to determine if there is a cause and effect occurring. The study depends on people reporting when they had an infection and what type they had, which may not always be reliable.
The study was published in the journal Annals of the Rheumatic Diseases.
