According to AARDA statistics, 50 million Americans suffer from autoimmune diseases, and the occurrences of many of the diseases are increasing.
Dr. Fred Miller, Director of the Environmental Autoimmunity Group at the National Institute of Environmental Health Sciences, says that the prevalence rates for some of these illnesses are rising for what must largely be environmental reasons. He says, "Our gene sequences aren't changing fast enough to account for the increase. Yet our environment is--we've got 80,000 chemicals approved for use in commerce, but we know very little about their immune effects." Dr. Miller adds, "Our lifestyles are also different than they were a few decades ago, and we're eating more processed food."
Writing in the July/August 2011 issue of Arthritis Today, rheumatologist and researcher Esther M. Sternberg, M.D., writes, "In any complex disease, the tendency to develop inflammation comes from genes, but whether it's arthritis, multiple sclerosis or something else depends on such environmental factors as bacteria, viruses, chemicals or foreign proteins.
"In addition, there is a 'dose effect' of genes--if you inherit many autoimmune genes, you will be more likely to get an autoimmune disease, regardless of environmental exposures. If you inherit very few, then environmental factors--from chemical exposure to major stress--become more important." Dr. Sternberg points out, "The genes load the gun and the environment pulls the trigger." The good news, she suggests, is that we can do something about our environment--avoid irritants like smoke and pesticides, minimize infections with hand washing, and learn ways to cope with stress.
Autoimmune diseases tend to cluster in families. For example, one child may have autoimmune hepatitis, another may have type 1 diabetes. Even though identical twins have the same genetic susceptibility to illness, it's possible that only one will develop an autoimmune condition. Dr. Noel R. Rose, Director, Johns Hopkins Center for Autoimmune Disease Research, and Chairman Emeritus, AARDA Scientific Advisory Board, comments that this suggests the involvement of environmental triggers. These may be defined broadly; chemicals, infectious agents, stress, hormones, diet, drugs, weight gain, and others. They all have been cited as factors causing autoimmune diseases.
Dr. Rose acknowledges that changes in diagnosis might account for some of the increase. He points out that there is a lot more clinical awareness now than there used to be. However, he says that there are some very good studies that show real increases, particularly for type 1 diabetes. There is compelling evidence to date that rising incidence is not simply an illusion based on better diagnosis.
Dr. Jill Norris, a professor of epidemiology at the Colorado School of Public Health, says, "We're probably seeing a mix of different trends." She says that where some autoimmune diseases are increasing, others are declining--for example, the prevalence of rheumatoid arthritis appears to be falling. "And for most others," she adds, "we don't know, mainly because we don't have the proper registries for tracking them."
Dr. Miller suggests "a national registry, something that would allow us to get a handle on disease hot spots in relation to certain environmental exposure." He adds, "With that, we'd also be able to see how these illnesses are changing over time." He points to the National Cancer Institute's Surveillance Epidemiology and End Results (SEER) program as an example of a successful registry. Dr. Miller says, "We don't have anything like that for autoimmune disease." The consequence, he points out, is that whereas cancers are often addressed as a single entity, autoimmune illnesses are put in disease-specific silos. This reduces the efficient use of research dollars.
The best evidence linking environmental exposures to autoimmune diseases so far comes from pharmaceutical drug studies, according to Dr. K. Michael Pollard, an associate professor at The Scripps Research Institute. He comments that two drugs in particular have been linked conclusively to systemic lupus erythematosus in a minority of patients: procainamide, a treatment for cardiac arrhythmia, and hydralazine, used for high blood pressure. "When you take patients off the drugs, their lupus symptoms go away," Dr. Pollard says. Also, gluten is linked with celiac disease.
Dr. Pollard observes that human evidence for other environment-disease links is more tenuous, partially because of inherent limitations in environmental epidemiology. Industrial compounds and chemicals are linked to autoimmune disease mainly by occupational studies in which exposures are more reliably gleaned from memory and work place records than they are in studies of the general population. Dr. Pollard says, "We need hard data on populations who are exposed and who are not exposed, and those studies aren't easy to do."
Dr. Rose observes, "We need more data associating autoimmune illness with specific exposures. And we also need plausible biological mechanisms to explain how those exposures produce or exacerbate disease. This will dominate our research agenda over the course of the next decade."
--Source: Excerpted from "Questions Persist, Environmental Factors in Autoimmune Disease," Charles W. Schmidt, MS, Environmental Health Perspectives, June 2011; "The Balance Within," Esther M. Sternberg, M.D., Arthritis Today, July/August 2011
