A history of taking antibiotics is associated with a higher risk of developing rheumatoid arthritis, a large case-control study suggests.
According to the UK study, recently published in BMC Medicine, the odds of developing rheumatoid arthritis were 60% higher among individuals exposed to one or more courses of antibiotics in the ten years prior to diagnosis than in their matched, unexposed controls.
The risk increased with the number of antibiotics courses. More recent exposure to antibiotics was also found to increase the odds of developing rheumatoid arthritis.
The researchers identified more than 22,000 patients with rheumatoid arthritis in primary care data and compared their history of infection and antibiotic prescription with more than 90,000 controls matched by gender, age and location.
The risk of RA also seemed to vary according to the class and mode of action of the antibiotic. Bactericidal antibiotics carried a higher risk than bacteriostatic (45% vs 31%).
The type of infection being treated appeared important, with respiratory tract infections showing the strongest association with RA.
“Although we have identified a strong association between antibiotic usage and the onset of RA, there remain many unanswered questions, particularly whether this is related to infections themselves, alterations in the microbiota, or a combination of the two,” the authors said.
The researchers suggested that gut microbiota disturbances might account for the link between antibiotics and the development of RA. They pointed to existing strong evidence linking antibiotic-induced microbiota disturbances to numerous conditions such as inflammatory bowel disease.
Professor Michelle Leech, a rheumatologist at Monash University, said the apparent link between antibiotics and later RA diagnosis might not be causal.
People who were genetically predisposed to RA might get more infections and take more antibiotics than the general population, she said.
“My question is; to what extent are patients with rheumatoid arthritis who received antibiotics actually having more infections and illnesses, compared to other people?” she said.
“Antibiotics affect the gut microbiota and the gut itself seems important in regulating the intensity of the immune system, but we can’t be sure about a causal link yet to rheumatoid arthritis.”