A Breath of Arthritic Air

Rheumatoid arthritis risk increases with rise in exposure to air pollution

(RxWiki News) Your environment can have a huge impact on your health. For example, your lungs can take a beating from breathing in polluted air. It now appears that substances like smog are also linked to rheumatoid arthritis.

People who are exposed to certain air pollutants may have an increased risk of rheumatoid arthritis.

"Be aware of the pollutant levels in the air."

Studies in the past have demonstrated a link between various environmental factors and the development of rheumatoid arthritis. For the purpose of two recent studies, researchers from Brigham and Women's Hospital in the United States and the Karolinska Institute in Sweden were interested in how pollutants in people's airways might play a role in the risk of rheumatoid arthritis.

More specifically, the researchers looked at how either gaseous pollutants (air pollution in the form of gas) or particulate pollutants (air pollution that contains small particles, such as soot or dust) might increase the risk of rheumatoid arthritis.

Neither the Swedish nor the American study found an increased risk of rheumatoid arthritis associated with particulate air pollution.

According to lead researcher Jaime Hart, M.D., of Brigham and Women's Hospital in Boston, "We were surprised that we did not observe evidence of an increased risk of [rheumatoid arthritis] with increasing levels of particulate matter, since our previous work had shown elevated risks of [rheumatoid arthritis] in women living close to major roads."

In contrast, the Swedish researchers found that a higher exposure to certain gaseous air pollutants (sulfur dioxide, nitrogen dioxide, or nitrogen oxide) was associated with a greater risk of rheumatoid arthritis.

The risk of rheumatoid arthritis increased by seven percent for people who went from a low to high exposure of sulfur dioxide. For those who went from a low to high exposure of nitrogen dioxide, the risk of rheumatoid arthritis grew by 11 percent. A rise in exposure to nitrogen oxide was associated with a seven percent increased risk of rheumatoid arthritis.

People without a university education (a measure of socioeconomic status) had a higher risk for disease, compared to those with a university education.

"This may be because individuals with a lower socioeconomic status are more likely to live in houses where more air pollution leaks in from the outside or other factors such as general health status that may make them more susceptible to the effects of air pollution," explains Dr. Hart in a news release from the American College of Rheumatology.

In comparison to the Swedish study, results from the American study showed only exposures to sulfur dioxide were linked to a higher risk of rheumatoid arthritis. When people increased their exposure to sulfur dioxide, there risk of rheumatoid arthritis grew by a modest five percent.

The differences in the findings between the two studies may be due to the differences between the participants in each study, explains Dr. Hart. The population in the American study - which consisted entirely of trained nurses - may have a relatively higher socioeconomic status of those involved in the Swedish study.

Dr. Hart says that both studies showed a modestly higher risk of rheumatoid arthritis among individuals with higher exposures to sulfur dioxide.

He also notes that this is the first study to look at the impact of air pollution on rheumatoid arthritis risk. As such, he concludes, "It is important to validate these findings in other studies, and in populations with a wide range of socioeconomic backgrounds."

For the Swedish study, researchers looked at 1,330 people with rheumatoid arthritis and 2,235 people without the disease. More than 91,000 women (762 of whom developed rheumatoid arthritis) from the US Nurses' Health Study participated in the American study.

The research was presented by Dr. Hart during the American College of Rheumatology's Annual Scientific Meeting.

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Review Date: 
November 21, 2011