MNT has some details:
“In 2007, the World Health Organization published a review that concluded night shift work is likely to raise the risk of cancer, particularly breast cancer. A new review of more than 1.4 million women challenges this conclusion, after revealing night shift work had little or no impact on breast cancer incidence.
Working night shifts has little or no impact on women’s risk of breast cancer, a new study suggests.
Study co-author Dr. Ruth Travis, of the Cancer Epidemiology Unit at Oxford University in the United Kingdom, and colleagues publish their findings in the Journal of the National Cancer Institute.
According to the Centers for Disease Control and Prevention (CDC), around 15 million adults in the United States work full-time night shifts, rotating shifts, or other irregular schedules.It is well established that such working patterns can disrupt the body’s circadian rhythm – the physical, mental, and behavioral changes that occur over a 24-hour cycle, which mainly respond to light and dark in the environment.
Circadian rhythm disruption has been associated with an array of health problems, including sleep disorders, obesity, diabetes, depression, and bipolar disorder.”
Source: Night shift work ‘does not raise breast cancer risk,’ study finds – Medical News Today