A new study provides further support that social activity with other children during the first few months of life protects against later risk of leukemia, say C. Gilham and colleagues.
What's Behind Day Care-Leukemia Link?
What's the apparent link between day care and leukemia risk? It's thought to be infections, say the researchers.
The idea that infections are behind the cause of childhood leukemia dates back to the 1940s.
Leukemia is cancer of white blood cells, immune system cells that fight off infection. In leukemia the bone marrow produces abnormal white blood cells that do not work normally. As the number of abnormal cells grows, they crowd out other blood cells, including normal white blood cells, red blood cells, and platelets. This overcrowding is what leads to symptoms, such as fatigue and bleeding, and can lead to death.
Cancer Success Story
Survival from leukemia varies widely depending on the type. Most children with leukemia have ALL (acute lymphoblastic leukemia).
The improvement in survival for children with ALL over the past 35 years is one of the great success stories of cancer treatment, according to the National Cancer Institute. Today, about 85% of children with ALL live five years or more. Five years is considered the cutoff by cancer experts that indicates likely long-term survival after cancer.
In the current study, Gilham looked at 3,800 children with cancer. Some of the kids had leukemia -- either ALL or another type -- and some had other forms of cancer. They were between 2 and 5 years old when they were diagnosed. Social activity and day care habits were compared with 7,600 children without cancer.
Formal Day Care Protects Most
Interaction with an older infant at least once a week that did not live in the same home was associated with a 34% decreased risk of ALL. Protection from other types of leukemia was similar.
When other types of cancer were taken together there was also a similar level of protection. However, when individual types of cancer were evaluated, risk was decreased only for central nervous system cancers, such as brain cancer.
When the results were looked at more closely, the researchers discovered that the protection from social activity mostly stemmed from formal day care. This included kids who attended day care for any amount of time, a playgroup at least two half-days a week, or at least two half-days a week in a smaller childcare setting with at least four children.
The more social activity or day care the child was exposed to, the lower the risk of ALL. The effect was most pronounced when the child attended day care within the first three months of life.
Infection Important for Child Health
Gilham's study is published in BMJ Online First. Gilham is a statistician at the Institute of Cancer Research in Sutton, England.
The researchers say that some degree of early exposure to infection seems to be important for child health. However, they add that more research is needed to determine the true effect and if the link is associated with any particular infection.