"Researchers in the UK and Israel found that when a light is turned on at night, it triggers an 'over-expression' of cells linked to the formation of cancer…The tests were carried out on mice at Leicester University by geneticist Professor Charalambos Kyriacou.
During the trial, a group of mice were exposed to a light for one hour. When compared with mice who had been kept in the dark, changes were found in cells in the brain responsible for the circadian clock which controls body function.
Dr Rachel Ben-Shlomo, of the University of Haifa, said in the journal Cancer Genetics and Cytogenetics that people waking at night would be best advised not to turn on the light: 'We believe that any turning on of artificial light in the night has an impact on the body clock. It's a very sensitive mechanism. If you want to get up to go to the toilet, you should avoid reaching for the light switch. There are some plug-in lights that just glow, that are safe and you could use them as an alternative.'"