lights at night

“If light were a drug, the government would not approve it,” says Professor Charles Czeisler of the Harvard Medical School. And Professor George Brainard of Thomas Jefferson University in Philadelphia, adds: “Humans evolved on a planet without electric light over thousands and thousands of generations. The body is designed to be alert and awake during daytime hours and to sleep at night. Now we have a 24-7 society that isn’t in harmony with our biological design.”

Studies show that light at night interferes with one of the body’s greatest natural defences against cancer – melatonin, dubbed “the hormone of darkness”. The hormone – which is secreted by the pineal gland at night, and particularly in the early hours of the morning – both impedes the growth of cancers and boosts the immune system.

Sleeping with the light on or staying up late could be a cause of breast cancer, authoritative new research suggests.

The research – which is being hailed as a “watershed”, providing “the first proof” of a link between artificial light at night and cancer – confirms a mass of the studies suggesting that modern life causes the disease by interfering with natural sleep cycles.

Carried out by the blue-chip National Cancer Institute and National Institute of Environmental Health Sciences in the United States, it offers a solution to the mystery of rising levels of breast cancer in rich countries, which are five times as high as in the developing world. One in 10 women will develop the disease.

Professor Richard Stevens of the University of Connecticut, who describes it as “a watershed study”, says: “Electric light as a driver of the breast-cancer epidemic worldwide – that’s a dramatic big thing.”

And Dr David Blask, who led the research – and calls it “the first proof that light is indeed a risk factor for cancer” – adds: “Breast tumours are awake during the day, and melatonin puts them to sleep at night.” Add artificial light and “cancer cells become insomniacs”.

Sleep Safely: What experts recommend

Shut out all light: Sleeping in a dark room aids production of neurotransmitter serotonin, which is crucial in making melatonin.

Get nine hours’ sleep: A Finnish study found that women who slept nine hours were one-third as likely to get breast cancer as those who slept seven-eight.

Get a red lightbulb: Place a red lightbulb in one fixture. If you get up in the night, only use this one.

Get outside in the morning: Just 10-15 minutes of morning light will send a strong time-keeping signal to the brain’s clock, leaving it less likely to be confused.

The story is at The Independent