New research has shown that working long-term night shifts is associated with an increased risk of several types of cancer in women.
According to the American Association for Cancer Research, women working long-term night shift work had an increased risk of cancer by 19%.
Xuelei Ma, PhD, an oncologist at State Key Laboratory of Biotherapy and Cancer Center said: "By systematically integrating a multitude of previous data, we found that night shift work was positively associated with several common cancers in women."
Ma and his colleagues performed analysis using data from 61 articles comprising 114,628 cancer cases and almost 4 million participants from North America, Europe, Australia, and Asia, to see whether or not long-term night shift work was associated with a risk of 11 types of cancer.
The research found that long-term night shift workers had an increased risk of developing breast, skin, and gastrointestinal cancer.
Nurses had the highest risk of developing breast cancer if they worked the night shift, out of all the different occupations that were analysed.
Ma added: "Nurses that worked the night shift were of a medical background and may have been more likely to undergo screening examinations."
"Another possible explanation for the increased cancer risk in this population may relate to the job requirements of night shift nursing, such as more intensive shifts."
The researchers also performed an analysis among breast cancer studies, and they found that the risk of breast cancer increased by 3.3% for every five years of night shift work.
Ma and his researchers found it surprising that there was a particular increased risk of breast cancer specifically in North America and Europe.
"We were surprised to see the association between night shift work and breast cancer risk only among women in North America and Europe."
"Our study indicates that night shift work serves as a risk factor for common cancers in women."
Ma said that these findings might help to implement measures to protect the health of female night shift workers, saying: "long-term night shift workers should have regular physical examinations and cancer screenings."
Ma added: "Given the expanding prevalence of shift work worldwide and the heavy public burden of cancers, we initiated this study to draw public attention to this issue so that more large cohort studies will be conducted to confirm these associations."