Female nurses who regularly work nights are significantly more likely to develop breast cancer and other common forms of the disease than those on day shifts, suggests a new study.
Researchers in China found women who worked nights long-term had an increased risk of common forms of cancer, compared with those who did not. However, the heightened risk was especially apparent among nurses.
“Increased cancer risk in this population may relate to the job requirements of night shift nursing”
In particular, there was a “remarkable” increase in breast cancer risk with nurses on nights being 58% more likely to get breast cancer than colleagues on day shifts.
Of all the occupations analysed, nurses had the highest risk of developing breast cancer if they worked the night shift.
Nurses who regularly worked nights were also 35% more likely to get gastrointestinal cancer and 28% more likely to get lung cancer compared to nurses on day shifts, found the analysis,
Meanwhile, the study found a “non-significant” increase in risk of ovarian cancer for nurses on nights and no effect when it came to cervical cancer.
It adds to a growing body of evidence linking long-term night shift work with increased cancer risk, though a major UK review in 2016 concluded there was no evidence of such an association, as previously reported by Nursing Times.
- Major review finds no cancer link to working nights
- Night shifts ‘linked to increased breast cancer risk’
- Regular night shifts linked to increased breast cancer risk
- Long-term night shifts can ‘double’ breast cancer risk
For the new analysis, researchers looked 67 studies involving more than 3.9 million people from North America, Europe, Australia and Asia, and more than 114,000 cases of cancer. Of those, 17 studies were specifically related to nursing.
Overall, the findings suggested long-term night shift work among women in general increased the risk of any form of cancer by 19%, said the researchers.
Female night shift workers were 41% more likely to get skin cancer, 32% more likely to get breast cancer and 18% more likely to get gastrointestinal cancer, the study found.
The findings, published in the journal Cancer Epidemiology, Biomarkers and Prevention, also suggested cancer risks increased the longer people spend working nights.
The research team calculated the risk of breast cancer increased by 3.3% for every five years of night shift work.
“Long-term night shift workers should have regular physical examinations and cancer screenings”
The increased cancer risk among nurses who work nights could be down to several factors, said lead researcher Xuelei Ma, an oncologist at Sichuan University.
One explanation might be that nurses on nights were more likely to get checked out and were, therefore, more likely to have a confirmed cancer diagnosis.
“Nurses that worked the night shift were of a medical background and may have been more likely to undergo screening examinations,” said Ms Ma.
“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,” she said.
Ms Ma said the study’s findings highlighted the need for health programmes and interventions to protect all women who often worked nights.
“Our study indicates that night shift work serves as a risk factor for common cancers in women,” she said. “These results might help establish and implement effective measures to protect female night shifters.”
She added: “Long-term night shift workers should have regular physical examinations and cancer screenings.”
Ms Ma said more research was needed into the relationship between night shift work and cancer – especially given shift work was becoming more common across the world.
The authors noted that one limitation of the latest piece of research was a lack of consistency between the studies analysed when it came to defining “long-term” night shift work.