Odds ratio for having rheumatoid arthritis with pack years of cigarettes smoked
| Pack years | Patients (%) | Controls (%) | Odds ratio3-150 (95% CI)3-151 |
Significance (p value) |
| 1–10 | 112 (47) | 161 (67) | 0.80 (0.44 to 1.50) | 0.496 |
| 11–20 | 15 (6) | 35 (15) | 0.55 (0.26 to 1.16) | 0.111 |
| 21–30 | 34 (14) | 26 (11) | 1.76 (0.95 to 3.29) | 0.068 |
| 31–40 | 30 (13) | 7 (3) | 5.72 (2.28 to 14.36) | <0.001 |
| 41–50 | 27 (11) | 4 (2) | 13.54 (2.89 to 63.38) | <0.001 |
| >50 | 21 (9) | 6 (3) | 8.41 (2.45 to 28.84) | <0.001 |
| Ever smoked | 155 (65) | 124 (52) | 1.81 (1.22 to 2.19) | 0.002 |