Table 5.

ORs for e-cigarette use by secondhand smoke exposure stratified by sex and school (N=12278)^b

	E-cigarette use	Total	Sex		High school
	% (95% CI)		Male	Female	Junior	Senior	Vocational
SHS home
No (Ref.)	3.2 (2.8–3.6)	1	1	1	1	1	1
Yes	7.5 (6.8–8.2)	1.53 (1.24–1.89)	1.42 (1.11–1.81)	1.82 (1.18–2.79)	1.27 (0.88–1.84)	1.67 (1.07–2.6)	1.81 (1.36–2.42)
SHS public
No (Ref.)	2.9 (2.4–3.5)	1	1	1	1	1	1
Yes	5.9 (5.4–6.4)	1.31 (1.04–1.64)	1.29 (0.99–1.69)	1.36 (0.89–2.07)	1.36 (0.93–2.01)	2.32 (1.26–4.29)	0.92 (0.68–1.23)
SHS level
Low (Ref.)	2.6 (2.2–3.1)	1	1	1	1	1	1
Medium	3.8 (3.3–4.4)	1.28 (1.00–1.64)	1.20 (0.90–1.61)	1.54 (0.95–2.47)	1.43 (0.93–2.21)	1.56 (0.84–2.90)	1.08 (0.79–1.47)
High	9.4 (8.5–10.4)	2.25 (1.77–2.87)	1.99 (1.50–2.64)	3.05 (1.90–4.87)	2.33 (1.52–3.56)	4.32 (2.41–7.74)	1.45 (1.07–1.96)
p for trend		<0.001	<0.001	<0.001	<0.001	<0.001	0.019
SHS (cont.)		1.10 (1.07–1.12)	1.08 (1.05–1.12)	1.12 (1.07–1.18)	1.09 (1.05–1.14)	1.18 (1.12–1.25)	1.03 (1.00–1.07)
SHS home and public
No (Ref.)	2.9 (2.4–3.5)	1	1	1	1	1	1
Home only	2.9 (1.9–4.2)	0.94 (0.58–1.52)	0.80 (0.45–1.44)	1.34 (0.56–3.20)	0.43 (0.13–1.47)	0.47 (0.06–3.89)	1.65 (0.94–2.88)
Public only	3.4 (2.9–4.0)	1.13 (0.85–1.49)	1.09 (0.78–1.52)	1.23 (0.72–2.10)	1.09 (0.70–1.71)	1.83 (0.92–3.64)	0.89 (0.61–1.30)
Both	8.1 (7.4–8.9)	1.89 (1.44–2.47)	1.72 (1.25–2.36)	2.36 (1.37–4.06)	1.58 (0.99–2.54)	3.36 (1.70–6.65)	1.66 (1.19–2.32)

OR: odds ratio.

^b: Model adjusted for age, sex, school type, district, boarding, local, GPA, pocket money, friends’ smoking, parents’ smoking and smoking status.