Evidence for and against the possibility that cigarette smoking predisposes to rheumatoid arthritis
| For | Against |
| Three prospective cohort studies show increased risk.6-8 | A retrospective case-control study showed a protective effect.12 |
| A population based case control study shows increased risk.9 | RA is more common in women than in men. Smoking is the opposite. |
| Monozygotic twin study shows increased risk for RA and smoking.10 | Little geographical variation in RA though in the developed world smoking levels vary considerably.5 13 |
| Smoking associates with rheumatoid factor production.5 | RA may be declining,13whereas cigarette smoking is generally increasing. |
| Atmospheric pollution can contribute to RF positivity, and clean air legislation may have led to its decline.11 | Smoking is generally more common in lower social classes, unlike RA.11 |
| RA is a modern disease and cigarette smoking is a modern epidemic. | Smoking reduces the risk of other chronic inflammatory diseases such as ulcerative colitis.14 |