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Tobacco smoke exposure and respiratory morbidity in young children
  1. A M Snodgrass1,
  2. P T Tan2,
  3. S E Soh3,4,
  4. A Goh1,
  5. L P Shek5,6,
  6. H P van Bever5,6,
  7. P D Gluckman3,7,
  8. K M Godfrey8,9,
  9. Y S Chong2,3,
  10. S M Saw10,
  11. K Kwek11,
  12. O H Teoh1,
  13. the GUSTO Study Group
    1. 1Department of Paediatric Medicine, KK Women's and Children's Hospital, Singapore, Singapore
    2. 2Department of Obstetrics & Gynaecology, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore, Singapore
    3. 3Singapore Institute for Clinical Sciences, Agency for Science and Technology Research (A*STAR), Brenner Centre for Molecular Medicine, Singapore, Singapore
    4. 4Department of Paediatrics, Yong Loo Lin School of Medicine, National University of Singapore, National University Health System, Singapore, Singapore
    5. 5Department of Paediatrics, Yong Loo Lin School of Medicine, National University of Singapore, Singapore, Singapore
    6. 6Khoo Teck Puat-National University Children's Medical Institute, National University Hospital, National University Health System, Singapore
    7. 7Liggins Institute, University of Auckland, Auckland, New Zealand
    8. 8Medical Research Council Lifecourse Epidemiology Unit, Southampton, UK
    9. 9NIHR Southampton Biomedical Research Centre, University of Southampton and University Hospital Southampton NHS Foundation Trust, Southampton, UK
    10. 10Saw Swee Hock School of Public Health, National University of Singapore, Singapore, Singapore
    11. 11Department of Maternal Fetal Medicine, KK Women's and Children's Hospital (KKH), Singapore, Singapore
    1. Correspondence to Dr AM Snodgrass, Department of Paediatric Medicine, KK Women's and Children's Hospital, Singapore, 100 Bukit Timah Road, Singapore 229899; amsnodgrass{at}


    Objective Secondhand smoke exposure is a potentially preventable cause of significant respiratory morbidity in young children. Our study aimed to quantify respiratory morbidity in young children exposed to secondhand smoke to identify potentially modifiable factors.

    Materials and methods This study was embedded in a prospective birth cohort study of pregnant women and their children from fetal life onwards in Singapore (Growing Up in Singapore Towards healthy Outcomes, or GUSTO). Data on prenatal, antenatal and postnatal active and secondhand tobacco smoke exposure were obtained by an investigator-administered questionnaire for the periods before pregnancy, at 26–28 weeks’ gestation and 24 months after delivery. Data on respiratory morbidity (wheezing episodes, croupy cough, nebuliser use, snoring) and other morbidity (fever, hospitalisation, ear infection) of the child was collected at week 3 and at months 3, 6, 9, 12, 15, 18 and 24 after delivery. Information on parental atopy and potential confounders such as socioeconomic status and maternal educational level were also obtained. Statistical analysis of the data was performed to quantify any significant differences in incidence of respiratory morbidity in children exposed to tobacco smoke in utero and postdelivery, compared with those in smoke-free environments.

    Results Women who smoked regularly prior to pregnancy comprised 12.5% (n=155) of the study population; this number fell to 2.3% (n=29) during pregnancy. Mothers exposed to secondhand smoke in the household before pregnancy comprised 35.7% of the study population (n=441) and 31.5% (n=389) were exposed during pregnancy. Postnatally, the prevalence of secondhand tobacco smoke exposure from birth to 2 years of age was 29% (n=359). Participants of Malay ethnicity (p<0.001), mothers with no or primary level education (p<0.001) and mothers with low socioeconomic status (p<0.001) had the highest exposure to tobacco smoke. Offspring secondhand smoke exposure at home by 12 months and by 24 months of age was associated with an increase in hospital admissions due to respiratory disease (RR 1.89, 95% CI 1.02 to 3.50, p=0.04 by 12 months and RR 1.64, 95% CI 1.05 to 2.55, p=0.03 by 24 months) as well as all-cause hospitalisation (RR 1.57, 95% CI 1.14 to 2.17, p=0.01 by 12 months and RR 1.49, 95% CI 1.17 to 1.90, p=0.001 by 24 months), adjusting for parental atopy and child atopic dermatitis. Participants exposed to secondhand smoke by 12 months postdelivery had a significantly increased risk of having at least one wheezing episode (RR 1.71, 95% CI 1.38 to 2.11, p<0.001).

    Conclusions Secondhand smoke exposure during the prenatal and postnatal periods is associated with increased respiratory morbidity in children. Opportunistic screening and targeted smoking cessation counselling for parents at child hospital admissions and well-child outpatient visits, as well as preconception smoking cessation counselling for future pregnancies, may be beneficial to protect the child from negative health impacts.

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