Breast Cancer and the Night Shift: Is There A Link?
Breast Cancer and the Night Shift: Is There A Link?
Oct. 16, 2001 -- Regularly working the night shift may put women at a slightly increased risk of breast cancer -- possibly because it disturbs natural sleep/wake cycles and biological functions.
Two new studies published this month in the Journal of the National Cancer Institute look at the issue. While the studies support other research regarding this link, some experts say it's all too preliminary for women to begin changing their lifestyles.
The focus of the research: the body's production of the hormone melatonin, produced on the 24-hour circadian biological cycle. While the body produces little melatonin during the day, production naturally increases during evening hours until it peaks at about 1 or 2 a.m.
Bright light at night seems to interrupt that cycle, significantly reducing the amount of melatonin that is produced, says Scott Davis, PhD, researcher at the Fred Hutchinson Cancer Research Center, and chair of epidemiology in the School of Public Health and Community Medicine at the University of Washington in Seattle. Davis is lead author of one of the JNCI studies.
Davis' study looked at two different nighttime light sources -- workplace light and ambient light in the bedroom at home. His study involved more than 800 Seattle area women aged 20 to 74 who were diagnosed with breast cancer and nearly 800 similarly-aged women who were not night-shift workers.
All were interviewed in person to gather information on numerous risk factors for breast cancer. They were also asked about sleep patterns and habits during the 10 years before diagnosis.
"Women who worked the graveyard shift at least once during that time had about 60% increased risk," Davis tells WebMD. "Moreover, the risk of breast cancer significantly increased with each additional hour per week of graveyard shift work."
Women whose bedrooms had lots of light while they were trying to sleep -- enough, or nearly enough, to read by -- also seemed to be at increased risk of breastcancer, he says.
The link between melatonin and breast cancer isn't completely understood, Davis tells WebMD. Melatonin regulates a number of hormone systems, including the production of estrogen by the ovaries. "When there is less melatonin, there is more estrogen, and estrogen affects the growth of breast tissue," he says.
Breast Cancer and the Night Shift: Is There A Link?
Oct. 16, 2001 -- Regularly working the night shift may put women at a slightly increased risk of breast cancer -- possibly because it disturbs natural sleep/wake cycles and biological functions.
Two new studies published this month in the Journal of the National Cancer Institute look at the issue. While the studies support other research regarding this link, some experts say it's all too preliminary for women to begin changing their lifestyles.
The focus of the research: the body's production of the hormone melatonin, produced on the 24-hour circadian biological cycle. While the body produces little melatonin during the day, production naturally increases during evening hours until it peaks at about 1 or 2 a.m.
Bright light at night seems to interrupt that cycle, significantly reducing the amount of melatonin that is produced, says Scott Davis, PhD, researcher at the Fred Hutchinson Cancer Research Center, and chair of epidemiology in the School of Public Health and Community Medicine at the University of Washington in Seattle. Davis is lead author of one of the JNCI studies.
Davis' study looked at two different nighttime light sources -- workplace light and ambient light in the bedroom at home. His study involved more than 800 Seattle area women aged 20 to 74 who were diagnosed with breast cancer and nearly 800 similarly-aged women who were not night-shift workers.
All were interviewed in person to gather information on numerous risk factors for breast cancer. They were also asked about sleep patterns and habits during the 10 years before diagnosis.
"Women who worked the graveyard shift at least once during that time had about 60% increased risk," Davis tells WebMD. "Moreover, the risk of breast cancer significantly increased with each additional hour per week of graveyard shift work."
Women whose bedrooms had lots of light while they were trying to sleep -- enough, or nearly enough, to read by -- also seemed to be at increased risk of breastcancer, he says.
The link between melatonin and breast cancer isn't completely understood, Davis tells WebMD. Melatonin regulates a number of hormone systems, including the production of estrogen by the ovaries. "When there is less melatonin, there is more estrogen, and estrogen affects the growth of breast tissue," he says.
