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Cancer Resources > Cancer News > 2004 > September

Sleeping with lights on might trigger cancer through melatonin suppression

Richard Woodman

Last Updated: 2004-09-08 9:01:01 -0400 (Reuters Health)

LONDON (Agence de Presse Medicale for Reuters Health) - Parents were advised on Wednesday not to allow children to sleep with the lights on because of the theoretical possibility that too much light at night could suppress levels of melatonin.

Russel Reiter, Professor of Cellular and Structural Biology at the University of Texas, said this was important because a reduction in melatonin had been linked to cancer initiation and cancer progression, he told the Children with Leukaemia conference in London.

"As an antioxidant, in many studies melatonin has been shown to protect DNA from oxidative damage. Once damaged, DNA may mutate and carcinogenesis may occur," he said.

"Likewise, lower than normal melatonin levels may exaggerate the growth of tumours since melatonin inhibits the uptake of fatty acid growth factors by cancer cells, inhibits telomerase activity and endothelin-1 synthesis..."

Reiter said night workers were known to have a higher risk of breast cancer. Studies also showed that blind people, who are not vulnerable to reduced melatonin levels through light at night, had a lower incidence of cancer.

He told APM that while there was still no proof that suppression of melatonin by light caused cancer, some precautionary measures should be taken. "There are parents who allow children to sleep with the lights on. This should be absolutely prohibited," he said.

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