Subjects unexposed to silica | Subjects exposed to silica | ||||||
---|---|---|---|---|---|---|---|
Smoking category | Category of RA | Number of cases/controls | OR* | 95% CI | Number of cases/controls | OR* | 95% CI |
Never-smokers | ACPA-positive RA | 57/193 | 1 | – | 6/17 | 1.15 | 0.42 to 3.15 |
ACPA-negative RA | 54/193 | 1 | – | 4/17 | 0.85 | 0.26 to 2.75 | |
RA overall | 25/193 | 1 | – | 10/17 | 0.86 | 0.37 to 1.98 | |
Ever-smokers | ACPA-positive RA | 176/284 | 2.53 | 1.72 to 3.72 | 38/41 | 4.08 | 2.31 to 7.21 |
ACPA-negative RA | 101/284 | 1.23 | 0.83 to 1.84 | 13/41 | 1.16 | 0.56 to 2.39 | |
RA overall | 297/284 | 1.69 | 1.26 to 2.27 | 56/41 | 2.35 | 1.46 to 3.80 | |
Ex-smokers | ACPA-positive RA | 99/174 | 2.52 | 1.63 to 3.89 | 17/28 | 2.84 | 1.39 to 5.84 |
ACPA-negative RA | 57/174 | 1.03 | 0.65 to 1.62 | 9/28 | 1.05 | 0.45 to 2.46 | |
RA overall | 171/174 | 1.58 | 1.14 to 2.20 | 28/28 | 1.71 | 0.94 to 3.08 | |
Current smokers | ACPA-positive RA | 77/110 | 2.78 | 1.77 to 4.38 | 21/13 | 7.36 | 3.31 to 16.38 |
ACPA-negative RA | 44/110 | 1.43 | 0.88 to 2.34 | 4/13 | 1.16 | 0.35 to 3.87 | |
RA overall | 126/110 | 1.85 | 1.30 to 2.65 | 28/13 | 3.64 | 1.78 to 7.46 |
↵* OR adjusted for the potential confounding from age and residential area.
ACPA, antibodies against citrullinated peptide antigens; RA, rheumatoid arthritis.