Children who attend day care or playgroups have about a 30% lower risk of developing the most common type of childhood leukaemia than those who do not, according to a new analysis of studies investigating the link.
The new research, to be presented today at the second CHILDREN with LEUKAEMIA Causes and Prevention of Childhood Leukaemia Conference in London, is the first comprehensive analysis of studies investigating the association between social contact and childhood leukaemia.
While the analysis does not reveal how intense social contact might ward off childhood leukaemia, it bolsters the theory that children exposed to common infections early in life gain protection from the disease. It is known that environments such as day care centres increase the chance of infections spreading. Some proponents of the theory believe that if the immune system is not challenged early in life and does not develop normally it may mount an inappropriate response to infections encountered later in childhood and that this could provoke the development of leukaemia.
"Combining the results from these studies together provided us with more confidence that the protective effect is real. 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," said the study's leader, Dr Patricia Buffler, professor of epidemiology at the School of Public Health of the University of California, Berkeley.