When registered nurse Terry Cogbill saw daylight, it used to be after a long night of work. It took a toll on her health.
"Your head is just really pounding, and then you feel jittery because you've been drinking coffee to stay awake," said Cogbill, who works at John Wayne Cancer Center.
Cogbill said she gained about 50 pounds while working nights. But now a new Canadian study finds other health concerns facing those on the night shift.
"What it generally suggests is that night-shift work greater than 30 years can increase risk of breast cancer in not only nurses but in other patient populations as well," said Dr. Maggie DiNome of the Margie Petersen Breast Center at St. John's Health Center.
Working night shifts interferes with your body's natural clock. It can lead to unhealthy eating, lack of exercise and weight gain -- all risk factors for cancer. But another theory is that it suppresses melatonin production, which may increase your risk for breast cancer.
"The idea is that melatonin can decrease the conversion or the production of estrogen in our body, and it can decrease the effect of our natural estrogen on our breast cells," said DiNome.
Reviews of numerous studies show the longer a woman works a night shift, the more likely her risk will increase, according to DiNome. But there's not enough evidence for doctors to recommend women make changes.
"Certainly what I don't want is for women who have this responsibility of having to work nights to take care of their family to feel guilty in any way," said DiNome.
"You have to do what you have to do," said Cogbill. "You don't really have a choice."
Cogbill got off the night shift after a couple of years. Her advice for the millions of Americans who have to work nights is to do what you can to find some balance.
"If your body can't get in the rhythm, I'd say try to limit the years of working that shift," said Cogbill.
Researchers suggest women who work nights maintain a healthy weight, exercise and reduce alcohol intake. Another concern Dr. DiNome brings up is the radiation emitted from cellphones and tablets. Preliminary research suggests a possible link between that and melatonin suppression.