Relative risk (RR) with 95% confidence interval (95% CI) of developing seropositive rheumatoid arthritis (RF+ RA), seronegative rheumatoid arthritis (RF− RA), and rheumatoid arthritis overall (total RA) for different categories of cigarette smokers compared with never-smokers by sex and age
| Current smokers compared with never-smokers | Ex-smokers compared with never-smokers | Ever-smokers compared with never-smokers | |||||||
|---|---|---|---|---|---|---|---|---|---|
| O* | RR† | 95% CI | O* | RR† | 95% CI | O* | RR † | 95% CI | |
| *O, number of exposed cases; †relative risk adjusted for age, and residential area; ‡RF status was unknown for two current smoking women aged 50–70. | |||||||||
| Women 18–70 years | |||||||||
| RF+ RA | 105 | 1.8 | 1.3 to 2.6 | 93 | 1.6 | 1.1 to 2.3 | 198 | 1.7 | 1.2 to 2.3 |
| RF− RA | 39 | 0.9 | 0.5 to 1.4 | 35 | 0.8 | 0.5 to 1.3 | 76 | 0.8 | 0.6 to 1.2 |
| Total RA | 146 | 1.4 | 1.0 to 2.0 | 128 | 1.2 | 0.9 to 1.7 | 274 | 1.3 | 1.0 to 1.7 |
| Women 18–49 years | |||||||||
| RF+ RA | 33 | 1.1 | 0.6 to 2.0 | 27 | 0.9 | 0.5 to 1.6 | 60 | 1.0 | 0.6 to 1.6 |
| RF− RA | 21 | 0.8 | 0.4 to 1.6 | 11 | 0.5 | 0.2 to 1.1 | 32 | 0.6 | 0.4 to 1.1 |
| Total RA | 54 | 1.0 | 0.6 to 1.6 | 38 | 0.7 | 0.4 to 1.2 | 92 | 0.8 | 0.5 to 1.3 |
| Women 50–70 years | |||||||||
| RF+ RA | 72 | 2.5 | 1.6 to 4.0 | 66 | 2.2 | 1.4 to 3.6 | 138 | 2.4 | 1.6 to 3.6 |
| RF− RA | 18 | 1.0 | 0.5 to 1.9 | 24 | 1.1 | 0.6 to 2.1 | 44 | 1.1 | 0.6 to 1.8 |
| Total RA‡ | 92 | 1.9 | 1.3 to 2.9 | 90 | 1.8 | 1.2 to 2.7 | 182 | 1.8 | 1.3 to 2.6 |
| Men 18–70 years | |||||||||
| RF+ RA | 34 | 1.8 | 0.8 to 4.1 | 47 | 1.9 | 0.9 to 3.8 | 81 | 1.9 | 1.0 to 3.5 |
| RF− RA | 12 | 0.7 | 0.3 to 1.6 | 19 | 0.9 | 0.4 to 1.9 | 31 | 0.8 | 0.4 to 1.6 |
| Total RA | 46 | 1.3 | 0.7 to 2.4 | 66 | 1.4 | 0.8 to 2.5 | 112 | 1.4 | 0.8 to 2.3 |
| Men 18–49 years | |||||||||
| RF+ RA | 6 | 0.9 | 0.2 to 4.0 | 13 | 1.1 | 0.3 to 3.4 | 19 | 1.2 | 0.5 to 3.4 |
| RF− RA | 3 | 0.5 | 0.1 to 2.9 | 6 | 1.3 | 0.3 to 5.0 | 9 | 1.0 | 0.3 to 3.4 |
| Total RA | 9 | 0.8 | 0.2 to 2.8 | 19 | 1.3 | 0.5 to 3.4 | 28 | 1.3 | 0.6 to 2.9 |
| Men 50–70 years | |||||||||
| RF+ RA | 28 | 2.5 | 0.9 to 7.0 | 34 | 2.6 | 1.0 to 6.3 | 62 | 2.4 | 1.0 to 5.5 |
| RF− RA | 9 | 0.8 | 0.3 to 2.1 | 13 | 0.7 | 0.3 to 1.9 | 22 | 0.7 | 0.3 to 1.7 |
| Total RA | 37 | 1.5 | 0.7 to 3.3 | 47 | 1.5 | 0.7 to 3.1 | 84 | 1.4 | 0.8 to 2.7 |