http://www.independent.co.uk/life-style/health-and-wellbeing/health-news/avoid-breast-cancer-sleep-in-the-dark-404522.html
Avoid breast cancer. Sleep in the dark...
... and you could reduce the chances of getting
breast cancer. Dramatic new research shows the risks to women of
artificial lights at night, in or out of bed
By Geoffrey Lean, Environment Editor
Sunday, 18 June 2006
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.
Experts believe that half
of the cancers are likely to be accounted for by family history,
smoking, drinking alcohol, diet, medicines, and such reproductive
factors as childlessness and having children late. But evidence has
been building up that electric light during the hours of darkness may
be responsible for much of the rest.
Repeated studies have shown
that night-shift workers - such as nurses or air stewardesses - are up
to 60 per cent more likely to get the disease. Another found that women
who stayed up late two or three times a week were similarly
susceptible. Conversely totally blind women are half as likely to
succumb to it.
"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.
Light, however, stops its production, making the body think it is daytime.In
the new study, scientists grafted human breast cancer tumours on to
rats and infused them with blood taken from women during the day, in
the early hours of the morning, and after being exposed to light at
night. The blood taken in darkness slowed the growth of the cancers by
80 per cent, but the blood taken after exposure to light accelerated it.
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 recommendShut 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.
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