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Play groups lower leukaemia risk by 30 per cent

29/04/2008

Children who go to day care centres or play groups have a 30 per cent reduced risk of developing the most common type of childhood leukaemia, a new study says.

The research does not show how social contact might help to prevent childhood leukaemia but it argues that children exposed to common infections in early life gain protection from the disease.

Some scientists say that if the immune system is not challenged early in life then it may not develop properly, resulting in an inappropriate response to infections encountered in later childhood.

This could then prompt the development of leukaemia, researchers say.

Today's research, which will be presented at a leukaemia conference in London, analysed 14 published studies involving a total of 6,108 children with leukaemia and 13,704 without the disease.

Researchers focused on acute lymphoblastic leukaemia (ALL), which accounts for more than 80 per cent of cases and most often occurs in children aged between two and five years.

Parents were asked about their children's social interaction, including day care and play group attendance.

Twelve of the studies found some indication of a protective effect of social interaction with other children, while two found no effect.

No study found that social contact increased the risk of childhood leukaemia.

"Combining the results from these studies together provided us with more confidence that the protective effect is real," said lead researcher Dr Patricia Buffler, professor of epidemiology at the school of public health of the University of California, Berkeley.

"Analysing the evidence in this way gives a more reliable answer to the question and a more precise estimate of the magnitude of the effect."

Another report released today at the Children with Leukaemia conference reviewed the evidence from studies that have investigated a link between infection and childhood leukaemia.

The researchers particularly looked at the role of infection during pregnancy and whether infection might be a factor influencing childhood leukaemia risk in situations where the population mix changes.

They concluded that whether infection during pregnancy or in situations of unusual patterns of population mixing influences the risk is inconclusive at present and that further research is necessary.

"Putting our review together with the new analysis on social interaction, we can say pretty confidently that childcare, breastfeeding and vaccination are good things," said Dr Adrienne Morgan, staff scientist at Children with Leukaemia.

"This gives a steer to the biologists looking for what mechanisms might be at play."