Table 2

Odds ratio (OR) with 95% CI of developing ACPA-positive RA, ACPA-negative RA and RA overall, respectively, among men with different combinations of silica exposure status and cigarette smoking, compared with men who were unexposed to silica and never-smokers

Subjects unexposed to silicaSubjects exposed to silica
Smoking categoryCategory of RANumber of cases/controlsOR*95% CINumber of cases/controlsOR*95% CI
Never-smokersACPA-positive RA57/19316/171.150.42 to 3.15
ACPA-negative RA54/19314/170.850.26 to 2.75
RA overall25/193110/170.860.37 to 1.98
Ever-smokersACPA-positive RA176/2842.531.72 to 3.7238/414.082.31 to 7.21
ACPA-negative RA101/2841.230.83 to 1.8413/411.160.56 to 2.39
RA overall297/2841.691.26 to 2.2756/412.351.46 to 3.80
Ex-smokersACPA-positive RA99/1742.521.63 to 3.8917/282.841.39 to 5.84
ACPA-negative RA57/1741.030.65 to 1.629/281.050.45 to 2.46
RA overall171/1741.581.14 to 2.2028/281.710.94 to 3.08
Current smokersACPA-positive RA77/1102.781.77 to 4.3821/137.363.31 to 16.38
ACPA-negative RA44/1101.430.88 to 2.344/131.160.35 to 3.87
RA overall126/1101.851.30 to 2.6528/133.641.78 to 7.46
  • * OR adjusted for the potential confounding from age and residential area.

  • ACPA, antibodies against citrullinated peptide antigens; RA, rheumatoid arthritis.