Adjusted ORs of respiratory symptoms for number of days of SHS exposure at home in never-smoking students (N=50 762)
| SHS at home (days/week) | N (%) | Respiratory symptoms (%) | Crude OR (95% CI) | Adjusted OR (95% CI) | |
|---|---|---|---|---|---|
| Model 1 | Model 2 | ||||
| From inside the home | |||||
| 0 | 40 575 (81.2) | 11.0 | 1 (reference) | 1 (reference) | 1 (reference) |
| 1–4 | 5295 (10.1) | 13.7 | 1.21 (1.11 to 1.32)*** | 1.18 (1.08 to 1.30)*** | 1.16 (1.06 to 1.27)** |
| 5–7 | 4652 (8.7) | 14.8 | 1.39 (1.27 to 1.52)*** | 1.34 (1.22 to 1.47)*** | 1.28 (1.17 to 1.41)*** |
| P for trend | – | – | <0.001 | <0.001 | <0.001 |
| Any exposure | 9947 (18.8) | 14.2 | 1.29 (1.21 to 1.38)*** | 1.26 (1.17 to 1.35)*** | 1.22 (1.14 to 1.31)*** |
| Per day increase | – | – | 1.05 (1.04 to 1.07)*** | 1.05 (1.03 to 1.06)*** | 1.04 (1.03 to 1.05)*** |
| From neighbours | |||||
| 0 | 42 924 (85.0) | 11.2 | 1 (reference) | 1 (reference) | 1 (reference) |
| 1–4 | 6148 (12.1) | 13.4 | 1.23 (1.14 to 1.33)*** | 1.23 (1.14 to 1.34)*** | 1.21 (1.12 to 1.31)*** |
| 5–7 | 1503 (2.9) | 17.2 | 1.74 (1.52 to 1.99)*** | 1.72 (1.51 to 1.95)*** | 1.63 (1.44 to 1.86)*** |
| P for trend | – | – | <0.001 | <0.001 | <0.001 |
| Any exposure | 7651 (15.0) | 14.2 | 1.33 (1.24 to 1.42)*** | 1.33 (1.23 to 1.43)*** | 1.29 (1.20 to 1.39)*** |
| Per day increase | – | – | 1.09 (1.07 to 1.11)*** | 1.09 (1.07 to 1.11)*** | 1.08 (1.06 to 1.10)*** |
Percentages were weighted by age, sex and grade.
Model 1: Adjusted for age, sex, highest parental education, housing type and school clustering effect.
Model 2: Adjusted for variables in model 1 and mutually adjusted for SHS exposure from inside the home and from neighbours.
*p<0.05, **p<0.01, ***p<0.001.
SHS, secondhand smoke.