Relative risk (RR) with 95% confidence interval (95% CI) of developing seropositive rheumatoid arthritis for 18–70 years old female and male subjects who have smoked cigarettes for ⩾20 years compared with never-smokers by intensity of smoking
Number of cigarettes smoked a day
Number of exposed cases
RR*
95% CI
*Relative risk adjusted for age, residential area, and sex.