Odds ratios for rheumatoid arthritis (rheumatoid factor positive, rheumatoid factor negative, and overall) for different combinations of silica exposure and cigarette smoking compared with never smokers unexposed to silica
| Absence of silica exposure | Silica exposure | |||||
|---|---|---|---|---|---|---|
| No of cases | OR* | 95% CI | No of cases | OR* | 95% CI | |
| *Adjusted for the potential confounding from age and residential area. | ||||||
| CI, confidence interval; OR, odds ratio; RA, rheumatoid arthritis; RF, rheumatoid factor. | ||||||
| RF+ RA | ||||||
| Never smoked | 27 | 1.0 | – | 3 | 1.8 | 0.4 to 9.0 |
| Ever smoked | 126 | 2.8 | 1.5 to 5.1 | 24 | 5.4 | 2.1 to 14.0 |
| RF− RA | ||||||
| Never smoked | 30 | 1.0 | – | 1 | 0.4 | 0.0 to 8.1 |
| Ever smoked | 45 | 0.4 | 0.2 to 1.0 | 13 | 1.6 | 0.4 to 7.2 |
| Total RA | ||||||
| Never smoked | 57 | 1.0 | – | 4 | 1.1 | 0.3 to 4.4 |
| Ever smoked | 171 | 1.4 | 0.9 to 2.3 | 37 | 3.7 | 1.7 to 8.1 |