We often hear about the benefits of diet and exercise for reducing cancer risk, but what about sleep? Mounting evidence shows that maintaining a consistent sleep schedule supports the body’s natural defences and may help lower the risk of developing certain cancers. In this article, we’ll explore the connection between sleep, circadian rhythm, and cancer, and how small changes to your bedtime routine could lead to big health benefits.
We spend one-third of our lives sleeping, so we must do what we can to get the best quality of sleep for our mental and physical health. If we don't get enough sleep, or the quality of that sleep is not good enough, there are multiple health implications, including a weakened immune system and an increased risk of certain cancers. This is especially true for shift workers. This article hopes to help you understand why sleep is so important and how it can help you reduce your risk of cancer.
The Science: How Sleep Affects Cancer Risk
The body has an internal clock, called the circadian rhythm, that helps regulate things like:
- Sleeping and waking up1
- Body temperature1
- The immune system1
- When our hormones are released1
- How your body uses and stores energy (metabolism)1
- How we handle stress1
If we regularly don’t get enough sleep, our bodies can’t function normally. This includes immune surveillance, the ability of our immune system to identify and eliminate an infection or cells that are behaving abnormally2,3. If these cells are not removed, they can be left to divide into other abnormal cells. In some cases, this can lead to pre-cancerous or cancerous growths developing over time2.
Melatonin as a protective hormone
Melatonin is a hormone that your body produces to help you fall asleep and have a good quality of rest throughout the night4. Levels are high during the night, when it is dark and fall during the day while it is light5.
Melatonin is also an antioxidant, which means that it can remove harmful substances from the body that may damage cells and cause them to behave abnormally. This makes it very good at reducing inflammation, supporting the immune system, and lowering the risk of cancer6. Some studies have shown that melatonin was able to slow the growth of cancer cells in a dish, in animals, and in humans7.
The problem is that when your eyes detect light, this stops melatonin production1,5, which can be a problem for those with insomnia or those who are shift workers.
Impact of chronic sleep deprivation
Chronic sleep deprivation is linked to higher risks of prostate, breast, and colorectal cancers2. This is likely due to repeated disruption of people’s circadian rhythm.
Without the antioxidant effect of melatonin against cell damage and weakened immune surveillance from poor sleep, the irregular routines seen in shift workers or insomniacs can increase the risk of developing these cancers4,7.
Shift workers are affected the most, with regular night shifts suppressing melatonin production for years; this can make people feel jet-lagged all the time. Simple habits may improve sleep quality and can help reduce these risks1.
How a Consistent Sleep Schedule Helps
Regulates hormonal balance
Melatonin can help regulate different hormones and help keep them within an optimal range. Some key hormones that can be influenced by melatonin include:
Oestrogen is a hormone that plays a key role in women’s reproductive health. High levels can increase the risk of breast and colorectal cancer. Increases in melatonin at night can help lower oestrogen production and dampen the effects of high oestrogen levels. Therefore, this could potentially help reduce the risk of developing these cancers8,9.
Cortisol is the body’s main stress hormone. High levels can affect your mental and physical health. Chronic stress can dampen your immune system and make you more vulnerable to illness and abnormal cell growth. Melatonin and cortisol follow opposing rhythms. So, the increase of melatonin and the decrease of cortisol at night can help ease the transition into rest and reduce the risks associated with chronic stress10.
Insulin is a hormone that helps you regulate your blood sugar by moving the sugar from the blood into cells that need it for energy. If insulin stops working, the sugar stays in the blood, and you can develop type-2 diabetes. The relationship between melatonin and insulin is complex and not completely understood, but melatonin is thought to reduce insulin sensitivity during sleep, which may help stop diabetics from experiencing dangerously low blood sugar at night9.
Strengthens immune response
Regular sleep strengthens immune function, particularly in white blood cells like T-cells or Natural Killer (NK) cells. These cells are crucial for early detection and destruction of abnormal or pre-cancerous cells. During good quality sleep, there are more of these cells, and they work more efficiently to carry out immune surveillance11,12. Poor quality sleep has been shown to reduce both NK and T-cell activity and can leave you vulnerable to infection and cancer13,14.
Small habits like having a regular sleep and wake time every day, and avoiding screen time for an hour or so before bed can help improve your immune system and keep you protected.
Reduces systemic inflammation
Poor sleep quality can cause chronic inflammation and make your body more susceptible to infection and cancer13. Inflammatory markers such as C-Reactive Protein (CRP) and interleukin-6 (IL-6) raise the alarm for the immune system and kick off the inflammatory process15.
The process is good for immediate threats like an infection, but if the body experiences chronic inflammation, healthy cells can be damaged, and the risk of tumours developing can increase16,17.
Common Sleep Disruptors and How to Avoid Them
An adult needs between 7 and 9 hours of good-quality sleep a night18. Many factors can prevent this, including:
- Shift work
- Jet lag
- Blue light emitted from screens
- Caffieine
- Inconsistent sleep/wake schedule
Having a good wind-down routine before going to bed can help increase the quality and quantity of sleep that you get. This can provide many benefits for your mental and physical health. Some tips and tricks the NHS suggests for improved sleep include:
- Consistent schedule: waking up and going to bed at the same time every day.
- Wind-down routine: avoiding screens and instead relaxing for an hour before bed.
- Optimal environment: keeping your room cool, dark, and quiet.
- Daytime habits: going outside in the daylight, exercising, limiting naps, and avoiding lying down or sitting too much.
- Avoid stimulants: no caffeine after midday, limiting alcohol and heavy meals before bed.
Better Sleep + Early Detection = Stronger Prevention
Lifestyle factors like sleep, diet, and exercise are important for mental and physical health.
Prevention is always better than a cure, and even visiting a healthcare professional once a year while you are feeling fit and healthy can provide peace of mind that you are in the best shape possible.
Proactive healthscreening can also help you spot changes in your health before they become a problem. This is especially helpful for chronic health conditions and cancers, which may not have symptoms. Pairing an annual check-up with pre-emptive health screening can be the best thing you can do for your well-being.
Ezra offers multi-organ MRI scans screen for potential signs of cancer in 14 organs. These scans are quick and carried out by experts.
Conclusion
Quality sleep isn't a luxury; it is essential for your general health and cancer prevention. Consistent sleep will help protect your melatonin production, circadian rhythm, balance hormones, and boost your immune system.
Shift workers and insomniacs face increased risks to their health, but simple fixes can help, including regular sleep schedules, limiting screen time, and properly winding down before bed. Prioritising regular and quality sleep is key to building long-term protection.
Make consistent sleep a cornerstone of your long-term health strategy and consider pairing it with proactive screening. Ezra’s MRI Scan can help detect early signs of cancer and other health conditions, giving you a clearer picture of your overall well-being. Book today!
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References
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5. NHS. About melatonin. nhs.uk. February 23, 2023. Accessed January 26, 2026. https://www.nhs.uk/medicines/melatonin/about-melatonin/
6. Chitimus DM, Popescu MR, Voiculescu SE, et al. Melatonin’s Impact on Antioxidative and Anti-Inflammatory Reprogramming in Homeostasis and Disease. Biomolecules. 2020;10(9):1211. doi:10.3390/biom10091211
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8. Orritt R. Why has science seemingly changed its mind on night shifts and breast cancer? Cancer Research UK - Cancer News. October 14, 2016. Accessed January 26, 2026. https://news.cancerresearchuk.org/2016/10/14/why-has-science-seemingly-changed-its-mind-on-night-shifts-and-breast-cancer/
9. Kim TW, Jeong JH, Hong SC. The Impact of Sleep and Circadian Disturbance on Hormones and Metabolism. Int J Endocrinol. 2015;2015:591729. doi:10.1155/2015/591729
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11. David Ray GK. Body clock affects how the immune system works – new findings. Body clock affects how the immune system works – new findings. Accessed January 26, 2026. https://www.manchester.ac.uk/about/news/body-clock-affects-how-the-immune-system-works--new-findings/
12. British Medical Assocaition. Fatigue and sleep deprivation. The British Medical Association is the trade union and professional body for doctors in the UK. Accessed January 26, 2026. https://www.bma.org.uk/advice-and-support/nhs-delivery-and-workforce/creating-a-healthy-workplace/fatigue-and-sleep-deprivation
13. Sleep Station. Sleep & immunity - why sleep is key to your immunity. Accessed January 26, 2026. https://www.sleepstation.org.uk/articles/health/sleep-and-immunity/
14. Garbarino S, Lanteri P, Bragazzi NL, Magnavita N, Scoditti E. Role of sleep deprivation in immune-related disease risk and outcomes. Commun Biol. 2021;4:1304. doi:10.1038/s42003-021-02825-4
15. Patel SR, Zhu X, Storfer-Isser A, et al. Sleep Duration and Biomarkers of Inflammation. Sleep. 2009;32(2):200-204. doi:10.1093/sleep/32.2.200
16. Haack M, Sanchez E, Mullington JM. Elevated Inflammatory Markers in Response to Prolonged Sleep Restriction Are Associated With Increased Pain Experience in Healthy Volunteers. Sleep. 2007;30(9):1145-1152. doi:10.1093/sleep/30.9.1145
17. Mennitti C, Farina G, Imperatore A, et al. How Does Physical Activity Modulate Hormone Responses? Biomolecules. 2024;14(11):1418. doi:10.3390/biom14111418
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