Table 4– Chronic obstructive pulmonary disease mortality per 100 Bq·m⁻³ mean county-level residential radon concentrations at enrolment in 1982 interacted with selected risk factors on the multiplicative scale, American Cancer Society Cancer Prevention Study-II

Characteristic	Deaths n	Fully adjusted HR^# (95% CI)	p-value
Age at enrolment yrs
<65	7800	1.10 (1.01–1.19)
≥65	5741	1.20 (1.08–1.33)	<0.01
Attained age yrs^¶
<70	2376	1.06 (0.91–1.24)
70–79	5500	1.18 (1.07–1.31)
≥80	5665	1.11 (1.00–1.23)	0.12
Sex
Male	7414	1.07 (0.98–1.17)
Female	6127	1.20 (1.09–1.33)	0.27
Education
Less than HS	2923	1.14 (0.99–1.33)
HS	4589	1.18 (1.05–1.32)
More than HS	6029	1.06 (0.95–1.19)	0.38
Cigarette smoking
Never	1797	1.03 (0.86–1.25)
Current	6585	1.13 (1.02–1.24)
Former	3912	1.08 (0.94–1.24)	0.24
Industrial exposures
No	10268	1.16 (1.07–1.26)
Yes	3273	1.03 (0.89–1.18)	0.21
Passive smoking at home⁺
None	1570	1.04 (0.85–1.27)
Any	227	1.03 (0.56–1.90)	0.89
Region^§
Northeast	2646	1.20 (1.10–1.31)
South	4359	0.94 (0.81–1.08)
Midwest	3695	1.12 (1.02–1.22)
West	2841	1.21 (1.10–1.32)	0.02
Ambient ozone concentrations^ƒ
<57.1 ppb	3232	1.21 (0.97–1.53)
≥57.1 ppb	3311	1.17 (1.01–1.36)	0.32

Data for radon concentration was obtained from the Lawrence Berkeley National Laboratory (Berkeley, CA, USA). HR: hazard ratio; HS: high school. ^#: age, race, sex and state stratified and adjusted for education, marital status, body mass index, body mass index squared, cigarette smoking status, cigarettes per day, cigarettes per day squared, duration of smoking, duration of smoking squared, age started smoking, passive smoking, vegetable/fruit/fibre consumption, fat consumption, industrial exposures, and occupation dirtiness index where appropriate; ^¶: race, sex and state stratified and adjusted for cigarette smoking status, cigarettes per day, cigarettes per day squared, duration of smoking, duration of smoking squared, age started smoking; ⁺: never-smokers; ^§: HR (95% confidence interval) and p-value were calculated without stratification by state; ^ƒ: participants with missing ozone data excluded cut-off points based on median participant ozone value.