The origin of rheumatoid arthritis (RA) is a mystery. All over the world, researchers are investigating the factors that may influence the processes that trigger the development of RA. Scientists have generally believed that RA is linked to the interaction between genetic and environmental factors.
For some time, research has indicated that smoking plays a significant role in the development of RA among people who are genetically predisposed to the condition. Recent research has confirmed this, showing that even light smoking increases the risk of developing RA. The rate of women who smoke has increased since the mid 1960s, which may be a factor in the rising incidence of RA among women described in the di scission below. Further suggesting a link, smoking has also been demonstrated to lower the response to biologic medications.
Air pollution is also emerging as a possible factor in the development of RA. One study found a link between traffic and the development of RA and mouse models have shown an increase in RA with exposure to diesel exhaust. New research also shows that fine particular air pollution appears to be associated with systemic autoimmune rheumatic diseases.
Previous studies on environmental and geographic factors
About 10 years ago, research from the Mayo Clinic showed that from 1995-2005, the incidence and prevalence of rheumatoid arthritis rose in women after having declined from the mid 1950s through the mid 1990s.
Since 1995, the incidence has risen from 36 women out of every 100,000 that developed rheumatoid arthritis each year, to 54 women of every 100,000. Interestingly, the incidence for men remained at about 29 per 100,000. Overall, the percentage of the entire population with the condition rose from 0.85 percent to 0.95 percent. At the time, researchers did not have a clear reason for the trend, but said that an environmental factor may have a role. It should be noted that this was a relatively small study, which included 350 adult patients from Olmsted County, Minnesota.
Another study published in the August 2008 issue of the Archives of Internal Medicine theorized that there may be a potential ecological association between living in states with higher air pollution and the risk of developing RA. This study found that women in New England and the Midwest, which have historically higher levels of industrial air pollution, were 37-45 percent more likely to develop RA than women in the West (pacific and mountain regions).
A Swedish study found that children who contract a serious infection within their first year have an increased risk of developing arthritis. They also found that low birth weight, premature delivery, or a longer-than-average pregnancy affected the risk of developing RA to a lesser degree. The study did not include information about the types of infections and geographic regions of these children. Since other studies have focused on air pollution and respiratory infections, it would be interesting to know if more of these children lived in industrial areas, and whether the illnesses requiring hospitalization were brought on by respiratory ailments.
There is an ever-growing list of areas to study to learn more about RA. It would be interesting to focus further research in regions where incidence of RA is rising to potentially begin to identify specific environmental factors, such as types of air pollution. This could influence future health and environmental policies more toward preventing exposure and minimizing risk and away from treatment of RA after it develops.