In a new study, Dr. Jaime E. Hart of Brigham and Women’s Hospital in Boston and colleagues did not find a correlation between pollutants and rheumatoid arthritis. According to Dr. Hart, “Overall, we did not observe any evidence that increases in pollution levels were associated with increases in the risk of rheumatoid arthritis.”
This study seemingly overturns findings by Dr. Hart from 2009 which suggested a connection between rheumatoid arthritis and air pollution. In both studies, the scientists monitored the health statistics of more than 100,000 nurse participants who took part in the Nurses’ Health Study between 1976 and 2006. Every two years, U.S. nurses were asked to fill out questionnaires about their health and answers were analyzed. In the 2009 study, the scientists used a geographic information system to determine distance to road at the residence of each nurse as a measure of traffic exposure. In most cases, the smaller the distance of residence to a source of traffic, the higher was the likelihood of developing rheumatoid arthritis. In the 2013 study, Dr. Hart and colleagues looked for the link between rheumatoid arthritis and individual pollutants, such as nitrogen dioxide and sulfur dioxide — and did not find one.
The study is an important step toward finding what causes (or does not cause, as the case may be) rheumatoid arthritis, which occurs when your immune system attacks the synovium — the lining of the membranes around your joints. Scientists think that genetic factors may leave you more susceptible to environmental factors, such as smoking, viruses and air pollutants — the 2013 study has not yet definitively ruled them out — that can trigger the disease. Indeed, in a study out this week from the University of Manchester and published in the Annals of the Rheumatic Diseases, the National Institute of Health’s Ian Bruce and his team looked into the association between lifestyle factors and the risk of developing rheumatoid arthritis. After monitoring a sample of over 25,000 people between 1993 and 1997, they found that smoking, obesity and having diabetes increased the risk or developing rheumatoid arthritis.
Studies such as Dr. Hart’s and Dr. Bruce’s are needed to find the links between genetic and environmental factors and how they contribute to the development of rheumatoid arthritis, so that effective disease screening tools and treatments can be found. Dr. Christopher Morris, a U.S. rheumatologist, said that until the triggering event that leads to rheumatoid arthritis is found, “we’re going to have this situation where we see conflicting data in different populations. It doesn’t change what we do to treat it.” With between .5 to 1.0 percent of the world’s population suffering from rheumatoid arthritis, new research into its cause is welcome. The possible elimination of pollution as a cause is a step forward for researchers into its etiology.