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Table 2 Unadjusted and adjusted odds of travelling in a car where smoking is allowed*

From: Smoking in cars in England: a study of school students in an English city

Variable

Number of students (% travel in car where smoking allowed)

Univariable model

Multivariable model

Odds ratio

Confidence interval

P-value

Odds ratio

Confidence interval

P-value

Sex

 Boy

2,072 (33.6)

1.00

 

0.044

   

 Girl

2,100 (37.3)

1.17

1.02-1.35

  

 Missing

20 (40.0)

1.32

0.67-2.59

  

School year

 Year 7

623 (31.0)

1.00

 

0.016

   

 Year 8

1,078 (35.4)

1.22

0.91-1.65

  

 Year 9

1,023 (34.9)

1.19

0.87-1.63

  

 Year 10

1,027 (36.1)

1.26

0.98-1.61

  

 Year 11

430 (41.9)

1.60

1.10-2.34

  

 Missing

11 (45.6)

1.86

0.33-10.47

  

Deprivation

 V (least deprived)

1,040 (26.6)

1.00

 

<0.001

1.00

 

0.009

 IV

446 (33.2)

1.37

1.05-1.78

1.13

0.87-1.46

 III

550 (37.5)

1.65

1.24-2.20

1.23

0.96-1.57

 II

501 (36.9)

1.61

1.30-2.00

1.15

0.90-1.48

 I (most deprived)

507 (48.5)

2.60

1.55-4.36

1.58

1.23-2.03

 Missing

1,148 (37.1)

1.63

1.19-2.21

1.05

0.86-1.27

Parental smoking

 Neither parent smokes

2,856 (24.4)

1.00

 

<0.001

1.00

 

<0.001

 One parent smokes

911 (55.4)

3.85

3.31-4.48

2.41

2.03-2.87

 Both parents smoke

395 (70.9)

7.54

5.92-9.61

3.37

2.60-4.38

 Missing

30 (20.0)

0.77

0.35-1.70

0.60

0.24-1.51

Sibling smoking

 None smokes

3,658 (32.7)

1.00

 

<0.001

1.00

 

0.006

 At least one smokes

504 (56.9)

2.73

2.09-3.55

1.36

1.10-1.70

 Missing

30 (20.0)

0.52

0.25-1.06

Omitted due to collinearity

Smoking in the main home

 Not allowed

3,495 (27.9)

1.00

 

<0.001

1.00

 

<0.001

 Allowed

660 (74.9)

7.70

6.99-8.49

3.89

3.14-4.81

 Missing

37 (54.1)

3.05

1.90-4.88

2.32

1.16-4.66

Friend smoking

 None

1,390 (24.0)

1.00

 

<0.001

1.00

 

<0.001

 One or two

594 (39.4)

2.06

1.72-2.47

1.67

1.33-2.09

 Three or more

1,179 (48.9)

3.03

2.43-3.78

2.09

1.73-2.51

 Not sure

1,004 (33.7)

1.61

1.32-1.96

1.34

1.10-1.62

 Missing

25 (28.0)

1.23

0.60-2.52

0.93

0.36-2.44

  1. *Only variables significant at multivariable level are presented for the multivariable model in this table.