Silica exposure is associated with increased risk of developing RA: EIRA-study

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Ann Rheum Dis. 2004 Aug 19 [Epub ahead of print]

Silica exposure is associated with increased risk of developing

rheumatoid arthritis: results from the Swedish EIRA-study.

Stolt P, Kallberg H, Lundberg I, Sjogren B, Klareskog L, Alfredsson L.

Institute of Environmental Medicine, Karolinska Institutet, Box 210,

S-171 77 Stockholm, Sweden.

OBJECTIVE: To study the association between silica exposure and

Rheumatoid Arthritis (RA) and how it is modified by cigarette smoking.

METHODS: Data from 276 male cases and 276 male controls aged 18-70

years, included into a Swedish population based study during May

1996-June 2001, were analysed. A case was defined as a person in the

study base who was recently diagnosed with RA according to the American

College of Rheumatology criteria. Controls were selected from the study

base as a stratified random sample considering age, gender and

residency. Men with self-reported history of work with rock drilling,

stone crushing, or of exposure to stone dust in general were defined as

silica exposed. Rheumatoid factor (RF) status among cases was registered

RESULTS: Silica exposed men had increased risk of RA, with an odds ratio

(OR), adjusted for age, residential area, and smoking, of 2.2 (95 %

confidence interval (95%CI) 1.2-3.9) among men aged 18-70 years and 2,7

(1.2-5.8) among men aged 50-70 years. Men who had worked with

rock-drilling or stone crushing (regarded as highly exposed) had a

slightly more marked increased risk of RA than silica exposed men in

general, with an OR of 3.0 (95%CI 1.2-7.6). The results regarding the

joint effect of silica exposure and smoking was compatible with, but not

conclusive for, a synergy between these two exposures in the development

of RA.

CONCLUSION: Silica exposure is associated with increased risk of

developing RA and this association is not explained by smoking habits.

PMID: 15319232

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