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Day care in infancy and risk of childhood acute lymphoblastic leukaemia: findings from UK case-control study

BMJ 2005; 330 doi: (Published 02 June 2005) Cite this as: BMJ 2005;330:1294
  1. C Gilham, statistician1,
  2. J Peto, professor of epidemiology2,
  3. J Simpson, research fellow3,
  4. E Roman, professor of epidemiology3,
  5. T O B Eden, professor of paediatric oncology (etim.eden{at},
  6. M F Greaves, professor of cell biology5,
  7. F E Alexander, professor of statistics6,
  8. for the UKCCS Investigators
  1. 1Cancer Research UK Epidemiology and Genetics Unit, Institute of Cancer Research, Sutton SM2 5NG
  2. 2Department of Epidemiology and Population Health, London School of Hygiene and Tropical Medicine, London WC1E 7HT
  3. 3Leukaemia Research Fund Epidemiology and Genetics Unit, Department ofHealth Sciences, University of York, York YO10 5DD
  4. 4Academic Unit of Paediatric Oncology, Christie Hospital and Central Manchester and Manchester Children's University Hospitals NHS Trusts, Manchester M20 4BX
  5. 5Section of Haemato Oncology, Institute of Cancer Research, London SW3 6JB
  6. 6Public Health Sciences, University of Edinburgh, Edinburgh EH8 9AG
  1. Correspondence to: T O B Eden
  • Accepted 15 March 2005


Objective To test the hypothesis that reduced exposure to common infections in the first year of life increases the risk of developing acute lymphoblastic leukaemia.

Design and setting The United Kingdom childhood cancer study (UKCCS) is a large population based case-control study of childhood cancer across 10 regions of the UK.

Participants 6305 children (aged 2-14 years) without cancer; 3140 children with cancer (diagnosed 1991-6), of whom 1286 had acute lymphoblastic leukaemia (ALL).

Main outcome measure Day care and social activity during the first year of life were used as proxies for potential exposure to infection in infancy.

Results Increasing levels of social activity were associated with consistent reductions in risk of ALL; a dose-response trend was seen. When children whose mothers reported no regular activity outside the family were used as the reference group, odds ratios for increasing levels of activity were 0.73 (95% confidence interval 0.62 to 0.87) for any social activity, 0.62 (0.51 to 0.75) for regular day care outside the home, and 0.48 (0.37 to 0.62) for formal day care (attendance at facility with at least four children at least twice a week) (P value for trend < 0.001). Although not as striking, results for non-ALL malignancies showed a similar pattern (P value for trend < 0.001). When children with non-ALL malignancies were taken as the reference group, a significant protective effect for ALL was seen only for formal day care (odds ratio = 0.69, 0.51 to 0.93; P = 0.02). Similar results were obtained for B cell precursor common ALL and other subgroups, as well as for cases diagnosed above and below age 5 years.

Conclusion These results support the hypothesis that reduced exposure to infection in the first few months of life increases the risk of developing acute lymphoblastic leukaemia.


  • Contributors FEA, TOBE, MFG, JP, ER, and JS were involved in the design and conduct of the study throughout. FEA, CG, JP, and JS were responsible for management and analysis of the data. All authors contributed to writing the manuscript. ER is the guarantor.

  • Funding Financial support has been provided by the Cancer Research Campaign and Imperial Cancer Research Fund (now Cancer Research UK), the Leukaemia Research Fund, and the Medical Research Council through grants to their units; by the Leukaemia Research Fund, the Department of Health, the Electricity Association, the Irish Electricity Supply Board, the National Grid Company, and Westlakes Research (Trading) through grants for the general expenses of the study; and by the Kay Kendall Leukaemia Fund for the associated laboratories studies. The investigation in Scotland is funded by the Scottish Office, Scottish Power, Scottish Hydro-Electric, and Scottish Nuclear.

  • Competing interests None declared.

  • Ethical approval See previous publications (references 6 and 23).

  • Accepted 15 March 2005
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