Exposure to infections in the first months and years of life is known to be necessary for normal development of immune system, and children who are not exposed may be more likely than those who are to develop leukemia and perhaps other diseases.

UKCCS ( The United Kingdom childhood cancer study ) investigators assessed the hypothesis that reduced exposure to common infections in the first year of life increases the risk of developing acute lymphoblastic leukemia.

UKCCS is a large population based case-control study of childhood cancer across 10 regions of the UK.

A total of 6305 children, aged 2-14 years, without cancer and 3140 children with cancer, diagnosed 1991-1996, were enrolled in the study.
Among cancer patients, 1286 had acute lymphoblastic leukemia ( ALL ).

Increasing levels of social activity outside the home were linked to consistent reductions in the risk of acute lymphoblastic leukemia.

The greatest reduction in risk ( 52 per cent ) was seen in children who attended formal day care ( attendance at facility with at least four children at least twice a week ) on a regular basis during the first three months of life.

The children exposed to informal day care outside the home had a lower ( 38 per cent ) risk of acute lymphoblastic leukemia, while those who had some social activity, but not day care, had a 27 per cent drop in the risk.

These results support the hypothesis that reduced exposure to infection in the first few months of life increases the risk of developing acute lymphoblastic leukemia.

Source: British Medical Journal, 2005


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