Nursery school may protect children from leukaemia

Children who attend nursery school might have a reduced risk of developing childhood leukaemia because their immune systems grow used to fighting infections, according to a study published yesterday.

Scientists in the US suggested the younger children started nursery, the longer they spent there and the higher the number of other children they came into contact with all lowered the risk.

Researchers believe childhood leukaemia could be caused by a rare immune response to common infections, although establishing how that is triggered remains elusive.

But the findings of the American study, published in the British Journal of Cancer, were said last night to have added to the theory.

This holds that delaying a child's exposure to infection, especially one born with an increased risk of developing the disease, might result in an underdeveloped immune system which responded to the infection by producing defective white cells.

The American scientists from the northern California childhood leukaemia study analysed 140 children, aged one to 14, who were diagnosed over four years with acute lymphoblastic leukaemia, a form of the disease that results from an accumulation of abnormal white cells. They were compared with children randomly selected from the California birth registry. Details of nursery attendance and interviews with children's guardians were included in the research.

Patricia Buffler, principal investigator of the study, said: "While our results strongly support the importance of the timing of infections in the development of childhood leukaemia, we are not able to distinguish whether a particular infection or a number of common infections are involved."

In Britain, the charity Cancer Research UK is funding a national childhood cancer study looking at the link between infections and leukaemia in 1,000 children.

Sir Paul Nurse, its interim chief executive, said the US research added to the increasing evidence that infections played a role in some cancers.

"Further investigation into exposure to infection with larger numbers of children should help us to identify the role of the immune system in childhood leukaemia and may lead to new ways to prevent the disease."