Background:
This study aimed to explore the association between household tobacco exposure and recent respiratory symptoms and medical service utilisations in Hong Kong young children.

Methods:
Analysis was performed on data obtained from a community-based cross-sectional pneumococcal carriage surveillance study of healthy children aged under 2 years. Information on demographics, household tobacco exposure status (any household smokers), household tobacco exposure level (total number of household smokers, total number of cigarettes consumed by household smokers per day), children's recent respiratory symptoms in 3 days and 1 month as well as children's recent medical services utilisation in 3 months were obtained by parent-reported questionnaires.

Results:
1541 subjects (mean age: 11.2 months, male: 50.7%) were recruited from June 2013 to June 2014. The prevalence of household tobacco exposure was 31.5%, prevalence of prenatal and postnatal maternal smoking were 1.6% and 3.5% respectively. After adjustment for potential confounders, children's household tobacco exposure (AOR=1.33, 95% CI: 1.03-1.70) and postnatal maternal smoking exposure (AOR=2.30, 95% CI: 1.09-4.85) were significantly and independently associated with all-cause doctor consultation in recent 3 months; postnatal maternal smoking exposure (AOR=2.70, 95% CI: 1.16-6.27) was significantly and independently associated with all-cause hospitalisation in recent 3 months. In addition, children with household smokers consuming more than 20 cigarettes/day (AOR= 3.47, 95% CI: 1.94-10.08) had adjusted higher risk of having recent respiratory symptoms in 1 month compared with those non exposed.

Conclusions:
Household tobacco exposure was associated with recent medical service utilisation and respiratory symptoms in Hong Kong young children. As home is the most significant source of environmental tobacco exposure for young children, efforts for reducing such exposure are essential.