higher risk for breast cancer， according to a study from Harvard T.H. Chan
School Of Public Health. The link was stronger among women who worked night
shifts.
Previous studies have suggested that exposure to light at night may lead to
decreased levels of the homone melatonin ， which can disrupt circadian
rhythms—our internal ’clocks’ that govern sleepiness and alertness—and， in turn，
lead to increased breast cancer risk.
The new study， the most comprehensive to date to examine possible links between
outdoor light at night and breast cancer， looked at data from nearly 110，000
women enrolled in the Nurses’ Health Study II from 1989-2013. The researchers
linked data from satellite images of Earth taken at night time to residential
addresses for each study participant， and also considered the influence of night
shift work. The study also factored in detailed information on a variety of
health and socioeconomic factors among participants.
Women exposed to the highest levels of outdoor light at night—those in the top
fift— had an estimated 14% increased risk of breast cancer during the study
period， as compared with women in the bottom fifth of exposure， the researchers
found. As levels of outdoor light at night increased， so did breast cancer
rates.
However， the association between outdoor light at night and breast cancer was
found only among women who were premenopausal and those who were current or past
smokers. In addition， the link was stronger among women who worked night shifts，
suggesting that exposure to light at night and night shift work contribute
jointly to breast cancer risk.
What can we learn from the first paragraph？
A.Women who live with higher levels of outdoor light may be at higher risk for cancer.
B.Men who live with higher levels of outdoor light may be at higher risk for cancer.
C.Women who worked night shifts may be at higher risk for breast cancer.
D.Men who worked night shifts may be at higher risk for breast cancer.
The underlined word in the Second Paragraph means_______.A.Awakening
B.awareness
C.wake
D.waking
According to previous studies， which of the following factors leads to increased breast cancer risk directly？A.Night shift work
B.Higher levels of outdoor light
C.Higher levels of the hormone melatonin
D.Health and socioeconomic factors
Which of the following can be the best title of the passage？A.Higher levels of outdoor light at night may be increasing the risk for breast cancer
B.The study of women’s work context
C.Higher levels of the hormone melatonin may be increasing the risk for breast cancer
D.The study of breast cancer
Which one is TURE？A.The association between outdoor light at night and breast cancer was found among all women.
B.According to the new study， as levels of outdoor light at night increased， so did breast cancer rates.
C.Women who were premenopausal were at lower risk for breast cancer.
D.Only night shift work contributes to breast cancer risk.
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