Attributable proportion (AP) due to interaction between ever-cigarette smoking, ex-cigarette smoking and current cigarette smoking, respectively, and silica exposure, associated with the risk of developing ACPA-positive RA and RA overall, respectively, with 95% CI
| Subjects exposed to silica | ||||
|---|---|---|---|---|
| Smoking category | Category of RA | Number of cases/controls | AP | 95% CI |
| Ever-cigarette smoking | ACPA-positive RA | 38/41 | 0.34 | −0.09 to 0.77 |
| RA overall | 56/41 | 0.34 | −0.09 to 0.77 | |
| Ex-cigarette smoking | ACPA-positive RA | 17/28 | 0.02 | −0.77 to 0.81 |
| RA overall | 28/28 | 0.14 | −0.53 to 0.81 | |
| Current cigarette smoking | ACPA-positive RA | 21/13 | 0.60 | 0.26 to 0.95 |
| RA overall | 28/13 | 0.52 | 0.12 to 0.93 | |
ACPA, antibodies against citrullinated peptide antigens; RA, rheumatoid arthritis.