Sending very young children to daycare centers and playgroups could help protect them from childhood leukemia, researchers said on Friday.
Some degree of exposure to common illnesses early on is important for the immune system, they agreed.
Unknown infections, along with a genetic default that occurs before birth, are the most likely cause of childhood leukemia, they added in a study.
“Early exposure to infections through social contact seems to be protective against the disease,” Professor Mel Greaves, of the Institute of Cancer Research in London, told a news conference.
An analysis of the results of the largest and most comprehensive study of childhood leukemia revealed that most cases of the disease originate in the womb when chromosomes break and exchange bits of their DNA.
But the disease is triggered by unknown infections during childhood that trigger an immune system response leading to the illness.
“Challenges to the immune system, possibly by infection, may be the main cause of leukemia,” said Dr. David Grant, of the Leukemia Research Fund in England.
Leukemia, a cancer of immature white blood cells, is the most common childhood cancer. It usually occurs between 2-4 years old and can be successfully treated in most cases.
Scientists have been puzzled by the causes of childhood leukemia since it was first diagnosed. But the 15-year United Kingdom Childhood Cancer Study, which involved more than 13,000 children including nearly 2,000 with leukemia, suggests that a double whammy -- the genetic default and the timing or pattern of infection early in life are critical.
“The crucial second event is some kind of infection,” said Greaves.
In a separate study to be published online by the British Medical Journal on Friday, scientists found that children who attend day care center or playgroups during the first few months of their life are less likely to develop leukemia.
“Our results provide further support that social activity with other infants and children during the first few months of life protects against acute lymphoblastic leukemia,” said Clare Gilham, of the Institute of Cancer Research, referring to the most common type of childhood leukemia.
“We conclude that some degree of early exposure to infection seems to be important for child health,” she added.
The scientists questioned the parents of 6,305 healthy children and 3,140 who had been diagnosed with leukemia between 1991-1996.
Babies who had gone to day care, a nursery school or a playgroup with other youngsters at least once a week during the first three months of their life had the greatest reduction in the risk of leukemia.
About 86 percent of the mothers of the healthy children said their children had some form of social activity outside the home during the first year of their life.
