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Is ambient air pollution associated with onset of sudden infant death syndrome: a case-crossover study in the UK
  1. Ian J Litchfield1,
  2. Jon G Ayres1,
  3. Jouni J K Jaakkola2,
  4. Nuredin I Mohammed1,3
  1. 1 Institute of Applied Health Research, College of Medical and Dental Sciences, University of Birmingham, Birmingham, UK
  2. 2 Center for Environmental and Respiratory Health Research, Faculty of Medicine, University of Oulu, Oulu, Finland
  3. 3 Medical Research Council Unit The Gambia, Banjul, Gambia
  1. Correspondence to Dr Ian J Litchfield; i.litchfield{at}


Objectives Air pollution has been associated with increased mortality and morbidity in several studies with indications that its effect could be more severe in children. This study examined the relationship between short-term variations in criteria air pollutants and occurrence of sudden infant death syndrome (SIDS).

Design We used a case-crossover study design which is widely applied in air pollution studies and particularly useful for estimating the risk of a rare acute outcome associated with short-term exposure.

Setting The study used data from the West Midlands region in the UK.

Participants We obtained daily time series data on SIDS mortality (ICD-9: 798.0 or ICD-10: R95) for the period 1996–2006 with a total of 211 SIDS events.

Primary outcome measures Daily counts of SIDS events.

Results For an IQR increase in previous day pollutant concentration, the percentage increases (95% CI) in SIDS were 16 (6 to 27) for PM10, 1 (−7 to 10) for SO2, 5 (−4 to 14) for CO, −17 (−27 to –6) for O3, 16 (2 to 31) for NO2 and 2 (−3 to 8) for NO after controlling for average temperature and national holidays. PM10 and NO2 showed relatively consistent association which persisted across different lag structures and after adjusting for copollutants.

Conclusions The results indicated ambient air pollutants, particularly PM10 and NO2, may show an association with increased SIDS mortality. Thus, future studies are recommended to understand possible mechanistic explanations on the role of air pollution on SIDS incidence and the ways in which we might reduce pollution exposure among infants.

  • epidemiology
  • community child health
  • cot death
  • paediatric thoracic medicine
  • public health

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  • Contributors IJL contributed to the conceptualisation of the study, initial drafting of the manuscript and supervised the research project at all stages. NIM contributed to the research design, performed the data management, analysis and interpretation, and with IJL drafted the initial manuscript. JGA contributed to the conceptualisation of the study, data interpretation and critically reviewed the manuscript. JJKJ contributed to the conceptualisation of the study, data interpretation and critically reviewed the manuscript. All authors approved the final manuscript as submitted.

  • Funding This work was supported by The Lullaby Trust, grant number 260.

  • Competing interests None declared.

  • Patient consent Not required.

  • Ethics approval Ethical approval was given by the University of Birmingham, Life and Health Sciences Ethical Review Committee.

  • Provenance and peer review Not commissioned; externally peer reviewed.

  • Data sharing statement No additional data are available.