BERLIN – Occupational exposures associated with increased risk of rheumatoid arthritis include jobs involving inhalation of chemicals or dusts as well as work in cold or humid conditions, according to data from a new Scandinavian case-control study.
Dr. Ritta-Sisko Koskela obtained detailed occupational exposure histories from more than 2,000 employed Finnish adults with rheumatoid arthritis (RA) and an equal number of hypertensive controls matched for age, occupation, gender, and region.
The impetus for the study was her observation that the age-adjusted prevalence of RA in Finland shows considerable geographic variation. Some of the highest rates occur in areas where certain industries are concentrated, such as mining, steel manufacturing, chemical processing, and ship dockyards, explained Dr. Koskela of the Finnish Institute of Occupational Health, Helsinki.
A prominent theme that emerged from the data is that occupationally linked RA seems to require a long duration of exposure and entails a lengthy latency period. For example, dock and warehouse workers with RA were 3.1-fold more likely to work under drafty conditions than were hypertensive dock workers without RA. The individuals with RA had a mean 15 years of exposure to drafty conditions, and they developed the disease an average of 20 years after this workplace exposure began.
And those were among the shortest exposure and latency times recorded in the entire study. For instance, chemical plant workers with RA were 6.9-fold more likely to have been working under cold conditions than were their coworkers without RA; they averaged a 26-year exposure history and a 29-year latency period. And metal workers with RA were 10.4-fold more likely to work with rubber and elastomers than were metal workers without RA; the workers with RA had an 18-year history of exposure to those chemicals and a 23-year latency phase, she said at the annual European Congress of Rheumatology.
Truckers with RA were 5.7- to 8.3-fold more likely to haul grain, concrete, or gas mixtures than were truckers without RA. And textile workers with RA were 8.7 times more likely to labor under humid conditions than were those without the disease. Farmers and foresters with RA were 2.1-fold more likely to work under high-humidity conditions and 6.1-fold more likely to experience infection by parasites or insect vectors than were those without RA.
Inhaled dusts linked to an increased prevalence of RA included synthetic mineral fibers, concrete, paints, pesticides, and carbonate minerals.
Dr. Koskela’s study builds on an earlier Swedish analysis of a national database including nearly 30,000 Swedes hospitalized for RA. That study identified certain occupations as being associated with increased risk, among them mining, farming, and electrical work, and in women nursing and social work (J. Rheumatol. 2008;35:986-91). The Finnish study takes things a step further by examining specific work-related factors within higher-risk occupations that distinguish those who develop RA from those who don’t. The aim is eventually to reduce the incidence of RA through avoidance of potentially modifiable exposures.
Dr. Koskela reported having no financial conflicts.