The association between tobacco and the risk of asthma, rhinoconjunctivitis and eczema in children and adolescents: analyses from Phase Three of the ISAAC programme
- Edwin A Mitchell1,
- Richard Beasley2,
- Ulrich Keil3,
- Stephen Montefort4,
- Joseph Odhiambo5,
- and the ISAAC Phase Three Study Group*
- 1Department of Paediatrics: Child and Youth Health, Faculty of Medical and Health Sciences, University of Auckland, Auckland, New Zealand
- 2Medical Research Institute of New Zealand, Wellington, New Zealand
- 3Institute of Epidemiology and Social Medicine, University of Muenster, Muenster, Germany
- 4Department of Medicine, University of Malta, Malta
- 5Centre Respiratory Diseases Research Unit, Kenya Medical Research Institute, Nairobi, Kenya
- Correspondence to Professor Edwin A Mitchell, Department of Paediatrics: Child and Youth Health, Faculty of Medical and Health Sciences, The University of Auckland, Private Bag 92019, Auckland, New Zealand;
Contributors EAM is a member of the ISAAC International Data Centre, ISAAC Steering Committee member, led the analysis and wrote the first draft. RB is a member of the ISAAC Steering Committee, regional coordinator for North America, and advised on the manuscript. UK is a member of the ISAAC Steering Committee, regional coordinator for Western Europe, and advised on the manuscript. SM is a member of the ISAAC Steering Committee, regional coordinator for Eastern Mediterranean, and advised on the manuscript. JO is a member of the ISAAC Steering Committee, regional coordinator for Africa, and advised on the manuscript. All authors approved the final submitted manuscript.
- Received 3 August 2011
- Accepted 16 May 2012
- Published Online First 12 June 2012
Background Exposure to parental smoking is associated with wheeze in early childhood, but in 2006 the US Surgeon General stated that the evidence is insufficient to infer a causal relationship between exposure and asthma in childhood and adolescents.
Aims To examine the association between maternal and paternal smoking and symptoms of asthma, eczema and rhinoconjunctivitis.
Methods Parents or guardians of children aged 6–7 years completed written questionnaires about symptoms of asthma, rhinoconjunctivitis and eczema, and several risk factors, including maternal smoking in the child's first year of life, current maternal smoking (and amount) and paternal smoking. Adolescents aged 13–14 years self completed the questionnaires on these symptoms and whether their parents currently smoked.
Results In the 6–7-year age group there were 220 407 children from 75 centres in 32 countries. In the 13–14-year age group there were 350 654 adolescents from 118 centres in 53 countries. Maternal and paternal smoking was associated with an increased risk of symptoms of asthma, eczema and rhinoconjunctivitis in both age groups, although the magnitude of the OR is higher for symptoms of asthma than the other outcomes. Maternal smoking is associated with higher ORs than paternal smoking. For asthma symptoms there is a clear dose relationship (1–9 cigarettes/day, OR 1.27; 10–19 cigarettes/day, OR 1.35; and 20+ cigarettes/day, OR 1.56). When maternal smoking in the child's first year of life and current maternal smoking are considered, the main effect is due to maternal smoking in the child's first year of life. There was no interaction between maternal and paternal smoking.
Conclusions This study has confirmed the importance of maternal smoking, and the separate and additional effect of paternal smoking. The presence of a dose–response effect relationship with asthma symptoms suggests that the relationship is causal, however for eczema and rhinoconjunctivitis causality is less certain.
- environmental tobacco smoke exposure
- asthma epidemiology
- tobacco and the lung
Funding Currently the main source of funding for the ISAAC International Data Centre (IIDC) is The New Zealand Lotteries Grant Board. Many New Zealand funding bodies have contributed support for the IIDC during the periods of fieldwork and data compilation (the Health Research Council of New Zealand, the Asthma and Respiratory Foundation of New Zealand, the Child Health Research Foundation, the Hawke's Bay Medical Research Foundation, the Waikato Medical Research Foundation, The Auckland Medical Research Foundation, Glaxo Wellcome New Zealand and Astra Zeneca New Zealand). Glaxo Wellcome International Medical Affairs and The BUPA Foundation supported the regional coordination for Phase Three and the IIDC. Without help from all of the above, ISAAC would not have been such a global success. EA Mitchell is supported by Cure Kids (NZ).
Competing interests None.
Ethics approval Each participating centres obtained approval according to their laws and regulations.
Provenance and peer review Not commissioned; externally peer reviewed.
Data sharing statement At this moment in time the data are confidential to each centre and the ISAAC International Data Centre.