New Study Links Daycare to Decreased Leukemia Risk

Though it’s bound to happen in any environment where there are children who don’t always cover their mouths when they sneeze, no one likes it when colds and viruses spread. But what if your child’s sniffles today could help protect him or her from a common childhood cancer tomorrow? A new study suggests that mild infections from exposing children to other children’s germs early on may actually protect them from leukemia.

For some time, scientists noticed that children who started daycare early in life were less likely to develop acute lymphoblastic leukemia (ALL), a cancer that happens when the body over-produces immature white blood cells that upset the balance of other cells in a child’s blood. This cancer causes anemia-like symptoms and carries a risk of bleeding. According to Science Magazine, B cells, which are “scouts of the immune system that patrol the bloodstream looking for intruders like viruses and bacteria,” normally are very adaptable, but when the immune system goes haywire, mutations in these cells cause leukemia.

The new study has determined why this cancer happens and established the link to early daycare decreasing a child’s risk for it. The study, recently published in Nature Immunology, outlines why the correlation might occur. When young children are exposed to minor infections or illnesses, it may “prime” their immune systems. Because leukemia is a result of the immune system going haywire, exposure to germs early in life may prevent this overreaction of the immune system that happens when a child gets many bacterial infections later in childhood.

The study also found a correlation between the vaccine Haemophilus influenza Type B (Hib) vaccine, which is used against a common bacterial infection that affects many young children, and a decreased instance of childhood ALL. Markus Muschen, senior author of the study, stated, “Hib and other childhood infections can cause recurrent and vehement immune responses, which we have found could lead to leukemia, but infants that have received vaccines are largely protected and acquire long-term immunity through very mild immune reactions.”

Science Magazine reported further by using the words of childhood leukemia researcher Joseph Wiemels: “It could also help explain seemingly contradictory findings that although early day care reduces ALL risk, that same risk is higher among children with more doctor visits. It could be that mild infections early in life, such as ones that often circulate in day cares, help build the immune system. More serious infections that warrant a trip to the doctor, however, could set off a damaging immune ‘storm.’”

Although the Hib vaccine does show some risk reduction on its own, Mel Greaves, a cancer cell biologist at the University of London’s Institute of Cancer Research, says the most striking reduction for ALL is in children who spend time in early daycare. In Science Magazine, Greave said, “If it [Hib vaccine] really worked as well as that, we wouldn’t have leukemia.”

Scientists are still working on various studies to see if certain infections are more likely to trigger genetic mutations that lead to ALL. They do not believe at this time that a single virus is always the cause, but Greaves is working on a study that points to one virus in a cluster of leukemia cases.

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