Cox regression analysis for time to first hospitalised respiratory tract infection after rheumatoid arthritis diagnosis
| Unadjusted, HR (95% CI) | Age-adjusted and sex-adjusted, HR (95% CI) | Fully adjusted*, HR (95% CI) | |
| Smoking status | |||
| Current vs never | 1.62 (1.28 to 2.06) | 2.18 (1.71 to 2.78) | 1.78 (1.38 to 2.29) |
| Current vs former | 0.79 (0.64 to 0.97) | 1.34 (1.09 to 1.67) | 1.29 (1.04 to 1.61) |
| Former vs never | 2.06 (1.69 to 2.52) | 1.62 (1.32 to 1.99) | 1.38 (1.12 to 1.7) |
| Smoking cessation | |||
| Per year since cessation, light smoker | 0.92 (0.84 to 1.01) | 0.86 (0.78 to 0.94) | 0.84 (0.76 to 0.92) |
| Per year since cessation, heavy smoker | 0.91 (0.82 to 1) | 0.83 (0.75 to 0.92) | 0.83 (0.75 to 0.92) |
| Heavy vs light smoker† | 1.43 (0.9 to 2.27) | 1.95 (1.21 to 3.14) | 1.37 (0.82 to 2.26) |
| Interaction‡ | 0.98 (0.9 to 1.08) | 0.96 (0.88 to 1.06) | 0.99 (0.9 to 1.09) |
HR, hazard ratio; CI, confidence interval.
*Adjusted for gender, age, Townsend score, year of diagnosis use of immunosuppressant disease-modifying antirheumatic drugs, use of oral glucocorticoids, type 2 diabetes, body mass index, asthma and chronic obstructive pulmonary disease.
†At the time of cessation.
‡Interaction between years of cessation and amount smoked.