Working at night can disrupt your body’s natural sleep-wake cycle, known as the circadian rhythm. This disruption has been linked to a range of health problems, including diabetes, heart disease, and certain types of cancer.

A new study adds to this evidence, suggesting that women who work night shifts may have an increased risk of breast, skin, and gastrointestinal cancers.

The Study

The study, published in the journal Environmental Research, examined data from over 100,000 female nurses who were part of the Nurses’ Health Study II.

The nurses were aged between 25 and 42 years old when the study began in 1989, and were followed up for over 20 years. During that time, 9,356 cases of cancer were diagnosed among the participants.

The Findings

The researchers found that women who worked night shifts for at least 30 years had a 19% higher risk of breast cancer, a 41% higher risk of skin cancer and a 32% higher risk of gastrointestinal cancer compared to those who had never worked night shifts. The risk was highest for those who worked rotating night shifts, rather than a fixed night shift schedule. The researchers suggest that this is because rotating night shifts disrupt the circadian rhythm to a greater extent than fixed night shifts.

The Mechanism

The study did not investigate why working night shifts might increase cancer risk.

However, other research has suggested that disruptions to the circadian rhythm can interfere with the body’s production of melatonin, a hormone that regulates sleep and has been shown to have anti-cancer effects. Night shift work has also been linked to an increased risk of inflammation and oxidative stress, both of which can promote cancer development.

The Implications

The findings of the study suggest that employers should take steps to reduce the risks associated with night shift work.

This might involve providing better lighting and ventilation, as well as allowing workers to take regular breaks and providing healthy food options. Employers might also consider offering flexible schedules that allow workers to rotate between day and night shifts more gradually, rather than suddenly switching between the two.

The Limitations

The study has some limitations. For example, it relied on self-reports of shift work, which may not be entirely accurate. The study also did not account for other potential risk factors, such as smoking, alcohol consumption, and family history of cancer.

However, the study’s large sample size and long follow-up period make the findings more robust.

The Conclusion

The study adds to the growing evidence that night shift work can have negative health effects, including an increased risk of cancer.

Women who work night shifts, especially those who have been doing so for a long time, should be aware of the potential risks and take steps to reduce them where possible. Employers also have a role to play in minimizing the negative impact of night shift work on their workers’ health.