'Artificial light increases breast cancer risk'

Roman Bystrianyk · medicine forum Guru Joined: 02 May 2005 Posts: 454

"'Artificial light increases breast cancer risk'", Daily Mail, June 19,
2006,
Link:
http://www.dailymail.co.uk/pages/live/articles/health/healthmain.html?in_article_id=391267&in_page_id=1774

Women who sleep with the light on or stay up late at night could be at
a greater risk of breast cancer, according to scientists.

Researchers have long suggested that being exposed to too much light at
night disrupts crucial hormones and raises the chance of developing
breast tumours.

Women who work night shifts - such as nurses and air stewardesses - are
thought to be particularly at risk.

Now, for the first time, scientists have demonstrated that long
exposure to artificial light could be cancerous.

The study by the American National Cancer Institute and National
Institute of Environmental Health Sciences could help explain the
rising levels of breast cancers in rich countries, where the risk of
developing cancer is five times higher than in underdeveloped
countries.

Breast cancer is the most common cancer in women in the UK, affecting
one in nine women at some point in their lives.

Around 41,000 women are diagnosed each year and each month in the UK
more than 1,000 die from the disease.

The study by American scientists showed that exposure at night to
artificial light stimulated the growth of human breast tumours by
suppressing the levels of the key hormone melatonin.

Melatonin is secreted by the pineal gland at night - and helps to
regulate a person's sleeping and waking cycles.

Light, however, stops the body from producing it, making the body think
that it is daytime.

The researchers proved the theory by grafting human breast cancer
tumours on to rats.

Blood samples from women were then pumped through the developing
tumours.

The blood had been collected under three different conditions - during
the day, in the early hours of the morning and after being exposed to
light at night.

Researchers found that the blood taken in darkness slowed the growth of
the cancers by 80 per cent.

And the blood taken after exposure to light appeared to stimulate
tumour growth.

Dr David Blask, a lead researcher on the study said it was "the first
proof that light is indeed a risk factor for cancer."

He added: "Evidence is emerging that disruption of a person's body
clock is associated with cancer in humans, and that interference with
internal timekeeping can tip the balance in favour of tumour
development."

If the link between tumour growth and light is confirmed by more
studies, it could result in a change in working patterns.

Lighting manufacturers could also be forced to develop products which
are more natural and similar to normal daylight.

Professor George Brianard, of the Thomas Jefferson University in
Philadelphia, aded: "Humans evolved on a planet without electric light
over thousands of thousands of generations.

"The body is designed to be alert and awake during the daytime hours
and to sleep at night. "Now we have a 24-7 society that isn't in
harmony with our biological design."

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