ARTIFICIAL LIGHT , BIOLOGICAL CLOCK DISRUPTIONS , INCREASE BREAST CANCER RISK
The disruption of a
person's circadian rhythm -- their 24-hour biological clock -- has been linked
to an increased risk of breast cancer, according to new University of Georgia
research. The culprit, in this study in particular, is artificial light.
"Exposure to
artificial light leads to a significantly higher risk for developing breast
cancer," said Chunla He, a biostatistics graduate student in the UGA
College of Public Health. "To decrease the use of artificial light, people
should avoid working at night and implement earlier bed times."
Her research,
published in the International Archives of Occupational and
Environmental Health, examined key studies that included risk factors for
developing breast cancer.
"A large body of
related research about circadian rhythms and breast cancer exists," He
said. "However, these studies are inconsistent and have a variety of
limitations."
Under the mentorship
of Sara Wagner Robb, assistant professor of epidemiology in the College of
Public Health, He turned to previous studies to see what the research revealed.
In addition to other
relevant exposures, He examined studies on breast cancer and flight attendants,
who typically work both day and night shifts. The flight attendants represented
a group of workers particularly susceptible to disrupted circadian rhythms,
which are heavily influenced by light.
In her analysis, He
found that employment as a flight attendant was related to an increased risk of
breast cancer.
"People naturally
secrete the hormone melatonin, which helps to regulate the circadian
rhythm," He said. "When the sleep-wake cycle is disrupted by
artificial light, melatonin secretion is adversely affected."
Robb recommends
spreading this information to shift workers so they understand the harms in
disrupting their circadian rhythms.
"Individuals
engaging in this type of work should be aware of these risks and may make
efforts to adjust their circadian rhythms," she said. "Although
additional studies are certainly needed, scientists are becoming increasingly
aware of the health risks associated with night workers and others exposed to
circadian-disrupting behaviors."
Robb and He also
advise that future research needs to examine social constraints -- which may
foster disruption of circadian rhythms -- on shift workers. Additionally, shift
workers should contact their primary care physicians for personalized treatment
and options.
"This information
tells us the harm in disrupting our natural cycle," He said. "With
this new analysis, we must be cautious in our exposure to artificial
light."
The article was
co-authored by Sonia Taj Anand, a former graduate student in the College of
Public Health; Mark H. Ebell, professor of epidemiology; and John E. Vena,
Medical University of South Carolina.
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