Night work raises breast cancer risk

Night work may increase a woman’s chances of developing breast cancer by 30% — a slightly elevated but “statistically significant” risk, researchers have said.

This places night work in the same order of risk as factors like genetic mutation, a late first pregnancy, or hormonal treatment, Pascal Guenel, director of French health research body Inserm, said.

Put into context, a smoker was eight times as likely to contract lung cancer as a woman working night shifts was to get breast cancer, he explained.

In a study published in the International Journal of Cancer, the researchers said an association between night work with breast cancer “was mainly observed in women working during overnight shifts, those who worked at night for 4.5 or more years, and less than three nights per week on average”.

“The association was stronger in women who worked at night before their first full-term pregnancy than in women who started working at night later in life.”

The study was conducted in France among 1,232 women diagnosed with breast cancer between 2005 and 2007.