In a world where most people wake up with the sun and head to their ‘9 to 5’, night shift work can be a challenge – but can it also be bad for your health? We explain how research indicates that while night shift work does not itself increase your risk of developing cancer, this type of working pattern may lead to other factors that do increase your risk.
Is working night shifts bad for your health?
Night shift work can make it harder to look after your health, as people tend to feel more tired, making exercising or healthy food choices more difficult. People who work shifts are also less likely to get enough sleep and more likely to be overweight or obese, both of which can have a significant impact on your overall health. And working non-standard patterns can put you at a higher risk for diseases like diabetes and heart disease, though more research is needed to better understand these risks.
Is night shift work a carcinogen?
In 2007, the International Agency for Research on Cancer (IARC) classified shift work that follows an irregular time pattern as a 'probable carcinogen' meaning it is likely to be a cause of cancer. This was based on some studies that found people who worked shifts or during the night were more likely to develop some types of cancer, such as breast and prostate cancer. It also came from the idea that disrupting the natural day/night cycle in your body, called your ‘circadian rhythm’, could have a negative impact on health. This is somewhat true as there are biological processes that are triggered by exposure to daylight, or by hormones that fluctuate over the course of the day.
What does the latest research say about night shifts and cancer risk?
In 2016, a meta-analysis (which combines the data of many different studies together) found no link between night shift work and breast cancer. In 2020, another meta-analysis that included data from 57 different studies and at least nine different types of cancer found no increased risk with night shift work.
So maybe night shifts are not causing cancer directly, but they could be influencing other health factors.
As a cancer research charity we were keen to better understand what was going on. Science funded by our Curestarters found that night shift workers are more likely to be overweight and have a high waist circumference, both of which are important risk factors for cancer. This research could inform new advice for night shift workers – for example by limiting the number of night shifts people are asked to work.
How can you reduce cancer risk if you work night shifts?
While night shift working does not itself appear to increase your risk of developing cancer, this type of working pattern may lead to other health behaviours or factors that increase your risk.
As a cancer charity, Worldwide Cancer Research recommends that whatever hours you work, the best way to reduce your cancer risk is always to look after your general health. You should aim to:
● Eat a balanced diet with plenty of fruit, vegetables, and fibre, and limit your consumption of red and processed meats.
● Moderate how much alcohol you drink
● Not smoke, or stop smoking!
● Get regular exercise that gets your heart pumping and do some resistance training.
Your night shift and cancer FAQs:
Does working night shifts disrupt your body clock?
If you work a 9-5 job you generally get up with the sun and sleep when it is dark, which helps to maintain your natural body clock. A lot of your bodily functions including heart rate, digestion and brain activity follow this 24 hour clock. Working a night shift is a reality for millions of people worldwide but it goes against this natural circadian rhythm. This can have health and wellbeing consequences for shift workers.
What are the cancer risk factors linked to night shift work?
Night shift work is quite a complicated factor to understand. It impacts your sleep, diet, and physical activity as well as exposing you to light at night-time. It could even alter your microbiome – the bacteria in your gut which can impact your health. All of these may play a role in the risk of developing cancer.
Why did the IARC classify night shift work as a probable carcinogen?
The IARC classified night shift work as probably carcinogenic based on the best available evidence at the time.
There is ongoing research around the world looking to better understand the link between night shift work and health. The more we can find out about this the more we can help night shift workers deal with the challenges they face.
Can a healthy lifestyle reduce the impact of night shift work?
All of us can struggle to maintain a healthy lifestyle but for night shift workers this can be even harder. Eating a balanced diet, reducing the amount of alcohol we drink, exercising regularly and not smoking are steps we can all take to reduce our risk of cancer.
More research is needed to understand how night shift work relates to cancer and how to help lower the risks involved.
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