Powerwatch News - 22/04/2005 - BBC give wrong conclusions on risk of childhood leukaemia

The BBC released news today concluding that a recent report "almost completely rules out" all causes of Leukaemia other than the lack of early exposure to infection in babies (< 1 year old). This is not only a complete misrepresentation of the report itself, but also a conclusion that is likely to be heavily damaging with regards to highly important funding into non-infection related Leukaemia Research.

CHILDREN with LEUKAEMIA organised a five day international scientific conference at Westminster in September 2004 that considered genetic susceptibility, infection, ionising radiation, chemicals in air, water and food, powerlines and microwaves, and the effect of light at night on melatonin production. All these have been shown to be associated with childhood leukaemia and need further investigation.

Report Title: Day care in infancy and risk of childhood acute lymphoblastic leukaemia: findings from UK case-control study
Objective: To test the hypothesis that reduced exposure to common infections in the first year of life increases the risk of developing acute lymphoblastic leukaemia.
Conclusion: These results support the hypothesis that reduced exposure to infection in the first few months of life increases the risk of developing acute lymphoblastic leukaemia.

Taken from report abstract

Firstly let us look at the actual conclusion of the report. What the objective is stating is that there may be a connection between lack of exposure to infection as a baby and future risk of developing ALL (Acute Lymphoblastic Leukaemia). Therefore when the conclusion states that the results support the hypothesis, this in no way excludes the possibility of other factors affecting the development of ALL, nor does it even suggest that exposure to infection (or lack of) is the major factor, merely that it has some detectable effect; it is saying is that if exposure did have an effect on incidence of acute lymphoblastic leukaemia, then one would expect to see the results that they observed.

In fact, the report's results are based almost exclusively on the increase of social interaction of the babies in question, by looking at those that had regular day-care attendance outside the home to those that did not. The report does not in fact actually look at infection rates, and therefore the increased exposure to infection is only assumed from attendance at the day care centres. As it is scientifically accepted that there is a small increase in infection at child day-care centres, this is a reasonable assumption, but it doesn't exclude other factors relating to day care centre attendance is being significant. This means that even under the conditions of the report itself we can only conclude that any noticed increase or decrease in incidence of Childhood Leukaemia may be linked to extra exposure to childhood infection.

For example, a good definition of what this particular study contributed to current scientific understanding is layed out as follows on the final page of the report:

"What is already known on this topic:
"Childhood leukaemia is a biologically diverse disease and is likely to arise by several aetiological pathways
"The common, B cell precursor, from of acute lymphoblastic leukaemia accounts for the incidence peak between 2 and 5 years of age, and immunological isolation may be a causal factor
"Children attending day care have an increased risk of contracting a variety of common infections
"What this study adds
"Children attending day care centres on a regular basis in the first few months of life are less likely to develop acute lymphoblastic leukaemia than are children who do not"

Day care in infancy and risk of childhood acute lymphoblastic leukaemia: findings from UK case-control study

So here we can see that the authors of the report themselves say that the results point towards a decreased incidence of ALL in children that attend day care centres, that may be attributable to an increased level of exposure to infection. Powerwatch fully accept the possibility of this, and it is our opinion that the report does indeed point towards the possibility of exposure to infection under 1 year of age having a preventative effect on chance of developing ALL.

What this report does not do in any way is look at the effect of any other currently postulated mechanisms, and therefore to conclude that nothing else can be considered a "significant risk" is both simply wrong and totally unscientific.