Breast cancer linked with night shifts - study
http://www.tiscali.co.uk/news/cgi-bin/newswire.cgi/news/reuters/topnews/ 2001/10/16/idsffh02291_2001-10-16_20-09-56_gri672901.html 16/10/2001 22:42 By Maggie Fox, Health and Science Correspondent WASHINGTON (Reuters) - Women who work night shifts may have a 60 percent greater risk of breast cancer, researchers have said. The finding may have to do with the body's response to light, the researchers, at the Fred Hutchison Cancer Research Centre in Seattle, said on Tuesday. A gland in the brain known as the pineal gland produces the hormone melatonin when the body is exposed to light -- sunlight or artificial light. This production is disrupted when people are up at night with the lights on. "Exposure to light at night may increase the risk of breast cancer by suppressing the normal nocturnal production of melatonin by the pineal gland which, in turn, could increase the release of oestrogen by the ovaries," the researchers wrote in their report, published in the Journal of the National Cancer Institute. Breast cancer is linked with production of oestrogen, the so-called female hormone. The researchers, led by Scott Davis, studied 813 patients aged 20 to 74 who had breast cancer, and compared them to 793 women who did not. They asked the women about work and sleep habits and bedroom lighting in the previous 10 years. "Graveyard shift work was associated with increased breast cancer risk," the researchers wrote. The increased risk was 60 percent -- a significant amount. And the more hours the women worked overnight, the higher the risk. The researchers said women had a twofold increase in the risk of breast cancer if they worked at least four and a half years of night shift work, during which they were awake at least three nights a week between 1 a.m. and 2 a.m. Davis said his team got the idea to check the links between light exposure and breast cancer after studies were done showing that blind women have a lower risk of breast cancer. They also said there was a very slightly higher risk of breast cancer in women whose bedrooms were the brightest at night. But getting up once in a while did not seem to increase risk. "Risk did not increase with interrupted sleep accompanied by turning on a light," Davis's team wrote. They said more study is needed before doctors start recommending that women avoid night shifts. For one thing, it may not actually be light that is causing the effect. "Among shift workers, quite a number of factors could affect the mechanisms that control the body's circadian rhythms," Davis said in a statement. "One is stress, considering the kinds of shift work, from police, fire and rescue work to nuclear power plant monitoring to factory work, medicine and nursing." "There is an urgent need for further exploration of the relationship between exposure to light at night, shift work, including timing during the night, and cancers that may be influenced by melatonin," Johnni Hansen of the Danish Cancer Society in Copenhagen, wrote in an editorial that accompanied the study. Risk of breast cancer goes up as a woman ages. The American Cancer Society says 197,000 people will get breast cancer this year and 40,000 will die of it. It is the second-biggest cancer killer of women, after lung cancer. C 2001 Reuters Click for restrictions THE END ==^================================================================ EASY UNSUBSCRIBE click here: http://topica.com/u/?bUrHhl.bVKZIr Or send an email To: [EMAIL PROTECTED] This email was sent to: [email protected] T O P I C A -- Register now to manage your mail! http://www.topica.com/partner/tag02/register ==^================================================================
