More than 8 million Americans suffer from autoimmune diseases, in which the immune system attacks the body's own tissues and several occupational exposures have been linked to systemic autoimmune diseases, which affect multiple organs. A new study published in the October issue of Arthritis & Rheumatism examined the possible associations between occupation and the risk of dying from systemic autoimmune diseases and found that occupational exposures in farming and industry may be linked to higher death rates from these diseases.
Led by L.S. Gold and A.J. De Roos, of the Fred Hutchinson Cancer Research Center in Seattle, WA, researchers examined death certificate data from 26 states from 1984 to 1998. Any cases that listed a systemic autoimmune disease (for example, rheumatoid arthritis) as a cause of death, were included, as were disease types with a suspected systemic autoimmune disease origin (such as unspecified connective tissue disorder). Five control subjects matched by age, sex, race, year of death and geographic region were also selected. The researchers established each person's longest-held occupation from the "usual occupation" listed on the death certificate. In addition, they examined specific exposures based on occupation and industry. These included asbestos, solvents, benzene, pesticides and other substances. Occupations involving significant exposure to the public (such as teachers, and waiters/waitresses) or animals were also tracked.
The results showed that some occupations involving exposure to the public (such as nurses and teachers) were associated with an increased risk of dying from a systemic autoimmune disease but this was not the case with all jobs involving public exposure (for example food service jobs). Farmers showed increased risk of death from systemic autoimmune disease, particularly for those who worked with crops versus livestock. In addition, several industrial occupations such as mining and textile machine operators, as well as timber cutting and logging had an increased risk of death from this group of diseases.
Further analysis showed that the same occupations and exposures were present in those who were older than the typical retirement age when they died, "implying that the occupational exposures were involved in a chronic pathogenic process leading to either disease incidence or slow progression of existing autoimmunity," according to the authors. They suggest that the higher risk associated with jobs involving public contact may be due to exposure to multiple infectious agents leading to an autoimmune response.
The authors note that autoimmune diseases tend to be underreported on death certificates, and that the increased risk seen with certain occupations, such as teachers, may be due to the fact that these individuals have extensive health benefits even after retirement, and therefore better access to care. This would also help explain why other occupations that involve public contact but lower health insurance coverage, such as waiter/waitress, seemed to have a lower risk of death from autoimmune disease. However, not all the occupational associations they found are expected to be affected by insurance status.
"The size of our study allowed us to estimate associations between specific occupations and death from autoimmune diseases and to generate hypotheses that will be useful as starting points for future studies in this area," the authors conclude. They note that future studies should focus on obtaining more detailed occupational histories from the groups found to be at increased risk.