Action Points
- Advise patients who ask that occupational exposure to mineral oils, particularly hydraulic and motor oils, may increase risk for rheumatoid arthritis in certain genetically susceptible individuals.
STOCKHOLM, Sept. 22-Changing the oil frequently may not help the joints.
Occupational exposure to mineral oils, particularly hydraulic and motor oils, increases the risk of developing rheumatoid arthritis by 60% in certain groups of patients, researchers here say.
Exposure increased the risk for rheumatoid factor-positive arthritis but not RF-negative arthritis, said Lars Klareskog, Ph.D., of the Karolinska Institute here and colleagues reported in a study published online today by
Arthritis Research & Therapy.
Following up on reports that mineral oils induced arthritis in mice, the Swedish research team studied 1,419 patients diagnosed with rheumatoid arthritis between May 1996 and December 2003 and 1,674 age- and sex-matched controls.
The population-based, case control study surveyed participants about their occupational exposure to different types of mineral oils. In addition, the researchers tested sera from participants for rheumatoid factor and anticitrulline antibodies. Finally, the researchers analyzed the genes of participants for the presence of HLA-DR shared epitope genes, which are known to increase the risk for rheumatoid arthritis in smokers.
A subset of 135 men reporting high exposure to mineral oils, mostly hydraulic and motor oils, was also compared with 132 matched controls.
After adjusting for smoking and other potentially confounding factors, oil exposure was associated with a relative risk for developing rheumatoid arthritis of 1.3 (95% confidence interval=1.0-1.7). When cases were divided into RF-positive and RF-negative disease, the increased risk was only observed for RF-positive arthritis (relative risk = 1.4, 95% confidence interval 1.0-2.0).
In addition, oil exposure was also associated with a 60% increased risk for anticitrulline-positive rheumatoid arthritis (RR=1.6, 95% CI=1.1-2.2).
Finally, the increased risk associated with oil exposure was not related to the presence of HLA-DR shared epitope genes.
The researchers noted that mineral oils activate the innate immune system, primarily in the lymph nodes, and they speculated that this could "trigger the activation of a cascade of events involving activated T lymphocytes, and that these events for as yet unknown reasons finally result in inflammatory joint disease."
The study authors added that "further exploration of this finding may be of interest in elucidating whether other types of adjuvants, such as microbial agents and other occupational agents, can also act as arthritis-inducing agents in humans."
