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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Collaborators The GUSTO study group includes Pratibha Agarwal, Arijit Biswas, Choon Looi Bong, Birit FP Broekman, Shirong Cai, Jerry Kok Yen Chan, Yiong Huak Chan, Cornelia Yin Ing Chee, Helen Y H Chen, Yin Bun Cheung, Audrey Chia, Amutha Chinnadurai, Chai Kiat Chng, Mary Foong-Fong Chong, YSC, Shang Chee Chong, Mei Chien Chua, Chun Ming Ding, Eric Andrew Finkelstein, Doris Fok, Marielle V Fortier, PDG, KMG, AG, Yam Thiam Daniel Goh, Joshua J Gooley, Wee Meng Han, Mark Hanson, Christiani Jeyakumar Henry, Joanna D Holbrook, Chin-Ying Hsu, Hazel Inskip, Jeevesh Kapur, KK, Ivy Yee-Man Lau, Bee Wah Lee, Yung Seng Lee, Ngee Lek, Sok Bee Lim, Yen-Ling Low, Iliana Magiati, Lourdes Mary Daniel, Michael Meaney, Cheryl Ngo, Krishnamoorthy Naiduvaje, Wei Wei Pang, Anqi Qiu, Boon Long Quah, Victor Samuel Rajadurai, Mary Rauff, Salome A Rebello, Jenny L Richmond, Anne Rifkin-Graboi, SMS, LPS, Allan Sheppard, Borys Shuter, Leher Singh, SES, Walter Stunkel, Lin Lin Su, Kok Hian Tan, OHT, Mya Thway Tint, HPvB, Rob M van Dam, Inez Bik Yun Wong, P C Wong, Fabian Yap and George Seow Heong Yeo.
Contributors All the authors had full access to all data in the study, and take responsibility for the integrity of the data and accuracy of the data analysis. AMS had the primary role in data analysis, data interpretation and writing of the report. PTT contributed to data collection, analysis, interpretation and report writing. SES, AG, LPS, HPvB, PDG, KMG, YSC, SMS and OHT contributed to the study design, data analysis, and interpretation and report writing. KK contributed to the study design.
Funding This research is supported by the Singapore National Research Foundation under its Translational and Clinical Research (TCR) Flagship Programme and administered by the Singapore Ministry of Health's National Medical Research Council (NMRC), Singapore, NMRC/TCR/004-NUS/2008; NMRC/TCR/012-NUHS/2014. Additional funding is provided by the Singapore Institute for Clinical Sciences, Agency for Science Technology and Research (A*STAR), Singapore. KMG is supported by the National Institute for Health Research through the NIHR Southampton Biomedical Research Centre and by the European Union’s Seventh Framework Programme (FP7/2007-2013), projects EarlyNutrition and ODIN under grant agreements numbers 289346 and 613977.
Competing interests None declared.
Patient consent Obtained.
Ethics approval This study received ethical approval from Singhealth Centralised Institutional Review Board (CIRB) and National Healthcare Group DSRB.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement Investigators interested in exploring the possibility of collaborations should contact lead principal investigator YSC (email@example.com), principal investigators SMS (firstname.lastname@example.org), KK (Kenneth.Kwek.YC@kkh.com.sg) and PDG (email@example.com). GUSTO has a website, mainly focused on information for the participants, at http://www.gusto.sg/. More information is also available on the website of the Translational Clinical Research (TCR) Flagship Programme on Developmental Pathways to Metabolic Disease, which is commonly known as Developmental Origins: Singapore (DeVOS), website http://devos.sg/