Table 2 Urinary cotinine concentrations (ng/mg creatinine) and univariate analysis for natural log-transformed cotinine concentrations of non-smoking residents of smoke-free homes^a

Type of housing

 Apartment

0.69 (0.55–0.86)

Reference

 Attached housing

1.18 (0.91–1.52)

0.54

0.17

0.002

 Detached housing

1.23 (0.96–1.58)

0.58

0.17

<0.001

Sex

 Men

1.56 (1.24–1.96)

Reference

 Women

0.76 (0.64–0.90)

−0.72

0.13

<0.0001

Age (year)

 19–39

0.80 (0.60–1.06)

Reference

 40–59

1.09 (0.90–1.32)

0.32

0.17

0.070

  ≥ 60

1.01 (0.80–1.27)

0.24

0.19

0.219

Education

 Middle school or less

1.09 (0.87–1.37)

Reference

 High school

0.89 (0.70–1.14)

−0.20

0.17

0.220

 College or higher

0.95 (0.70–1.28)

−0.14

0.19

0.436

Household income (USD/month)

  ≤ 1000

1.21 (0.92–1.59)

Reference

 1001–2000

1.02 (0.80–1.31)

−0.16

0.16

0.297

 2001–3000

0.81 (0.62–1.07)

−0.39

0.20

0.045

  > 3000

0.91 (0.69–1.21)

−0.28

0.21

0.175

Former smoker

 Never smoked

0.79 (0.68–0.93)

Reference

  > 1 year not smoking

1.70 (1.27–2.27)

0.76

0.15

<0.0001

  ≤ 1 year not smoking

3.91 (2.32–6.60)

1.60

0.27

<0.0001

Frequency of SHS odor (times/week)

 None

0.93 (0.79–1.10)

Reference

 1–2

0.99 (0.71–1.37)

0.05

0.17

0.762

 3–6

1.33 (0.83–2.13)

0.35

0.24

0.140

 Every day

2.07 (1.11–3.88)

0.80

0.33

0.017

Duration of SHS odor (min/day)

 None

0.93 (0.79–1.10)

Reference

 1–5

1.17 (0.72–1.91)

0.23

0.27

0.395

 6–30

1.32 (0.90–1.94)

0.35

0.21

0.095

  ≥ 31

1.30 (0.78–2.20)

0.33

0.25

0.185