Table 2.

Crude^a- and multivariate^b adjusted hazard ratio (HR) estimates for lung cancer with 95% confidence intervals (CIs) for different measures of smoking exposures, the Norwegian Women and Cancer Study, 1991–2015.

Smoking exposures	Cases (n)	HRa (95% CI)	HRb (95% CI)
Neverc	43	1.00 (ref)	1.00 (ref)
Passive	53	1.33 (0.89–2.01)	1.34 (0.89–2.01)
Former	348	3.81 (2.77–5.23)	3.69 (2.68–5.09)
Current	1139	15.44 (11.37–20.98)	13.88 (10.18–18.91)
Ever	1464	7.67 (5.66–10.41)	6.80 (5.00–9.24)
Smoking duration in ever smokersd
1–9	231	4.58 (3.29–6.39)	4.16 (2.98–5.82)
10–19	203	4.24 (3.05–5.91)	4.22 (3.02–5.90)
20–29	429	9.26 (6.75–12.71)	8.55 (6.20–11.77)
≥30	595	18.11 (13.25–24.74)	16.48 (12.02–22.60)
P-trende		<0.001	<0.001
Cigarettes smoked per day in ever smokersd
1–9	376	4.46 (3.57–5.58)	4.28 (3.42–5.37)
10–19	767	13.16 (10.65–16.28)	12.17 (9.81–15.10)
>20	125	23.07 (17.70–30.06)	21.66 (16.54–28.37)
P-trende		<0.001	<0.001
Pack-years in ever smokersd
1–5	199	4.01 (2.89–5.57)	3.81 (2.73–5.31)
6–15	429	8.40 (6.13–11.50)	7.90 (5.74–10.86)
>15	671	22.52 (16.53–30.69)	21.24 (15.52–29.06)
P-trende		<0.001	<0.001
Age at smoking initiation in ever smokersd
>20	334	6.33 (4.84–7.62)	5.76 (4.55–7.28)
17–20	739	9.95 (8.04–12.31)	9.08 (7.31–11.27)
≤17	315	6.07 (4.84–7.61)	5.70 (4.53–7.17)
P-trende		<0.001	<0.001

^aAdjusted for age.

^bAdjusted for age, duration of education and alcohol consumption, all at enrolment.

^cNever-active, never-passive smokers as reference group.

^dThe sum of cases in each interval in smoking duration, cigarettes day, pack-years and age at smoking initiation does not sum up to the total number of cases in ever smokers because of missing values.

^eTest for trend excluding never smokers.