Can Working Night Shifts Increase Cancer Risk?

In the United States, about 15 million people have irregular work patterns, including night shifts, that can put them at risk for cancer.

Several studies have found that disrupting your body’s natural rhythm guided by the cycles of day and night is potentially hazardous for your health in several ways.

This increased risk is especially true for female night shift workers. According to a recent study published in Cancer Epidemiology, Biomarkers & Prevention, women who work night shifts over long periods of time are at risk for skin, breast, and digestive cancers.

Female Workers at Increased Risk for Cancer

The research on night shift workers looked at data from over 61 studies that included nearly four million people from across North America, Asia, and Australia.

The combined results showed a pattern of illness for women who worked night shifts for long periods of time. Compared to other women who worked irregular shifts, night workers had:

• 41% higher risk of skin cancer
• 32% higher risk of breast cancer
• 18% greater risk of digestive system cancers

The overall risk of cancer for women who worked night shifts increased by 19%.

The study also found the risk of breast cancer for these women became greater over time. For every five years of night shift work, the risk of breast cancer went up by 3.3%.

Although night-shifts are rising in popularity and gaining social acceptance, this does not decrease the adverse affects of this unhealthy practice.

How Night Shifts Affect Cancer Risk

More research is needed to fully understand the risks of working night shift, though sleep disturbances can affect the body in several potentially hazardous ways.

One possible theory is that exposure to artificial light during a night shift disrupts the body’s circadian rhythm. This is your body’s natural responses to the changes in light over 24 hours.

Melatonin

When it’s dark at night, your brain sends a signal to your body to release melatonin, which is a hormone that affects sleep. Being exposed to artificial light can interrupt these daily signals, leading to less melatonin.

This may possibly lead to cancer growth because it deprives the body of melatonin’s antioxidant abilities. Melatonin helps your body fight off cancer cells and limits new blood vessel growth that can lead to tumors.

Genes

Disrupting your circadian rhythm may also affect certain genes that regulate how cells grow. Unusual sleep patterns can cause cell metabolism, growth, and division to increase, which are all features that can lead to cancer.

Sex Hormones

Night shift work also causes an increase in sex hormones (like estrogen), which is a likely cause of breast cancer.

Xuelei Ma, Ph.D., of WC Medical Center, suggests that long-term night-shift workers should have regular physical examinations and cancer screenings.

Cancer Prevention Options

Though you may not be able to choose the time of your shift, you can take other steps to protect your health:

• Keep up with recommended cancer screenings for early detection
• Practice a well-balanced, plant-heavy diet
• Make sleep a priority between night shifts
• Stop smoking

See our article on the top 5 lifestyle changes for cancer prevention for the more information on cancer risk factors within your control.