Table 2

Prevalence of secondhand smoke (SHS) exposure, parental smoking status and respiratory symptoms (%)*

Year 2006Year 2008
(n=3243)All schools (n=4965)p Value†Follow-up schools (n=3057)p Value‡
SHS exposure at home in the past 7 days
 None89.886.0<0.00186.9<0.001
 1–3 days4.86.40.0036.80.001
 4–7 days5.47.7<0.0016.40.03
 Any days10.214.1<0.00113.2<0.001
SHS exposure outside home in the past 7 days
 None80.272.8<0.00172.7<0.001
 1–3 days14.317.9<0.00119.4<0.001
 4–7 days5.59.4<0.0018.0<0.001
 Any days19.827.2<0.00127.4<0.001
SHS exposure anywhere in the past 7 days
 None76.868.8<0.00168.9<0.001
 1–3 days14.418.0<0.00118.4<0.001
 4–7 days8.813.1<0.00112.7<0.001
 Any days23.231.2<0.00131.1<0.001
Smoking status of parents
 Father only29.527.60.6027.40.61
 Mother only1.62.10.081.70.46
 Both5.04.70.864.70.72
 None63.965.00.9466.20.69
Places of SHS exposure outside home in the past 30 days
 Streets–34.4N/A35.6N/A
 Parks–15.4N/A15.8N/A
 Restaurants–13.4N/A12.3N/A
 Bus stops–12.7N/A12.7N/A
 Subways–9.5N/A10.0N/A
 Wash rooms–9.2N/A9.8N/A
 Shopping malls–8.0N/A7.7N/A
 Playgrounds–7.7N/A7.3N/A
 Others' homes–6.0N/A6.6N/A
Respiratory symptoms
 Yes36.638.5<0.00138.4<0.001

  • ↵* Data were weighted by school grade distribution according to Hong Kong Annual Digest of Statistic in 2006 and 2008.

  • ↵† p For χ2 comparison between 2006 schools and all schools in 2008.

  • ↵‡ p For χ2 comparison between 2006 schools and follow-up schools in 2008.