Relative risk of having rheumatoid nodules in ever smokers compared with never smokers by duration of smoking, stratified for being rheumatoid factor positive or negative
| Smoking years | RF positive patients (74 male, 66 female) | RF negative patients (32 male, 35 female) | ||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Cases (n) | Controls (n) | OR | 95% CI | Cases (n) | Controls (n) | OR | 95% CI | |||||||||
| CI, confidence interval; OR, odds ratio; ref, reference; RF, rheumatoid factor. | ||||||||||||||||
| 0 | 4 | 37 | 1.0 (ref) | 5 | 23 | 1.0 (ref) | ||||||||||
| 1 to 25 | 12 | 18 | 6.8 | 1.9 to 24.6 | 4 | 12 | 1.2 | 0.2 to 5.9 | ||||||||
| 26 to 35 | 19 | 17 | 10.9 | 3.2 to 37.3 | 2 | 8 | 1.4 | 0.2 to 9.2 | ||||||||
| >35 | 15 | 18 | 8.5 | 2.4 to 30.2 | 3 | 10 | 1.4 | 0.2 to 8.5 | ||||||||
| Total | 50 | 90 | 14 | 53 | ||||||||||||