Table 4

Crude and adjusted risk ratios with 95% confidence intervals for developing lung cancer among 16 209 middle aged men living in Oslo in 1972 with a 10 µg/m3 increase in average yearly nitrogen oxides exposure in 1974 to 1978, analysed in different strata of smoking by Cox regression analyses

cRRaRR95% CI
Adjusted risk ratios are controlled for education and age (age as a continuous variable).
*Not adjustment for education (coefficient did not converge).
†The small number of observations make the regression analysis of limited value.
aRR, adjusted risk ratio; CI, confidence interval; cRR, crude risk ratio.
Non-smoker1.20*1.200.70 to 2.03
1–9 cigarettes/day1.241.250.98 to 1.58
10–19 cigarettes/day1.071.060.96 to 1.17
20+ cigarettes/day1.071.060.96 to 1.18
†Smoker, amount not reported/former smoker1.191.190.93 to 1.53