International experts will today consider the evidence for a link between the rise in childhood leukaemia and increased light at night at an international scientific conference in London.
The incidence of childhood leukaemia increased dramatically in the twentieth century. The increase has mainly affected the under five age group, in whom the risk increased by more than 50 per cent during the second half of the century alone.
Although the causes of leukaemia in children are poorly understood, environmental factors are thought to play a major role in the rising incidence since changes in our genetic make up simply do not happen on this kind of timescale. If this is the case, then it may be possible to take preventative measures, but first we need to determine what these factors are.
This is the driving force behind the conference – Childhood leukaemia: incidence, causal mechanisms and prevention – which is being hosted by CHILDREN with LEUKAEMIA, Britain’s leading charity devoted to the conquest of the disease.
Whilst the link between leukaemia and light at night may, on the surface, seem surprising, it has a logical basis and there is considerable evidence pointing towards the association. Compared with 100 years ago we are exposed to considerable light at night (LAN) during the natural hours of darkness. LAN disrupts our natural circadian rhythm, suppressing the normal nocturnal production of the hormone melatonin.
As Russel Reiter, Professor of Cellular and Structural Biology at the University of Texas, explains, a reduction in melatonin has been linked to cancer initiation as well as cancer progression. "As an anti oxidant, in many studies melatonin has been shown to protect DNA from oxidative damage. Once damaged, DNA may mutate and carcinogenesis may occur."
A number of studies have shown that people in occupations that expose them to LAN (i.e. night workers) experience a higher risk of breast cancer and that blind people, who are not vulnerable to reduced melatonin levels through LAN, have a lower incidence of cancer.