This type of work usually done at call centers placed them at a high risk for developing breast cancer. "Nighttime sleep deprivation or exposure to light at night somehow interrupts melatonin production, which in turn stimulates the ovaries to kick out extra estrogen, a known hormonal promoter of breast cancer," he said. Colina added that the study had showed that the risk of developing the cancer increased by as much as 60 percent.
Nighttime work may also play havoc with the menstrual cycle. "Painful menstruation (dysmenorrhea), absence of menstruation (amenorrhea), and heavy menstruation (menorrhagia) are conditions associated with women taking the graveyard shift," Colina said. "Although the study isn't conclusive, it provides us [with] pointers on how to address and protect the occupational health and safety of working women at call centers."
Call centers must take a note of the study and provide free and regular breast cancer screening for their employees, he added.