Table 6

Relative risk (RR) with 95% confidence interval (95% CI) of developing seropositive rheumatoid arthritis for 18–70 years old female and male ever-smokers compared with never-smokers by cumulative dose of smoking

Number of pack-yearsNumber of exposed casesRR*95% CI
*Relative risk adjusted for age, residential area, and sex.
<10651.00.7 to 1.5
10–19781.81.2 to 2.6
⩾201362.71.8 to 3.9