The cancer risk of disrupted sleep

Cancer is a group of diseases where cells grow out of control forming tumours. The cancer cases are increasing worldwide and World Health Organization (WHO) warns that cancer cases could jump by 77% by 2050, with over 35 million new cases worldwide. A carcinogen is substance that causes cancer, like chemicals, radiation, or even certain lifestyle habits. One surprising carcinogen is night shift work, that changes body’s natural rhythms. The International Agency for Research on Cancer (IARC) calls night shift work a “probable” cause of cancer because it disrupts the body’s internal clock, known as the circadian rhythm. Let’s explore why this happens and how we can lower the risks.

The Role of Melatonin and Our Body’s Clock:

Our body has a built-in clock called the circadian rhythm, which controls sleep, metabolism, and immune function. It’s an internal schedule that syncs with the day-night cycle. A hormone called melatonin, made by penial gland in the brain, helps regulate this clock and signals when it’s time to sleep. Melatonin production kicks in when it’s dark, but light—especially blue light from phones, tablets, or computers—can stop it. This blue light, most intense between 446 and 477 nanometers, tricks the brain into thinking it’s daytime, keeping us awake and reducing melatonin.

The circadian rhythm is closely tied to how cells grow and divide, a process called the cell cycle. Proteins that control our body’s clock, like CLOCK, BMAL1, and PER2, also help manage cell division. When the circadian rhythm gets out of whack—say, from staying up late or working night shifts these proteins don’t work properly which leads to abnormal cell growth and cancer.

Why Night Shifts and Screen Time Are Risky:

Night shift work, common in jobs like healthcare or manufacturing, forces people to stay awake when their body expects to sleep. This disrupts melatonin production and throws off the circadian rhythm. Over time, this disruption can lead to health problems like trouble sleeping, weight gain, heart issues, diabetes, and even brain-related conditions. Most worryingly, studies show night shift workers have a higher risk of cancers like breast, prostate, colorectal, and lung cancer. Melatonin may also help stop cancer cells from spreading, so lower levels due to disrupted rhythms could make cancer more likely to grow or spread.

How to Lower the Risk:

The good news is that small changes can help keep your body’s clock in sync and possibly reduce cancer risk. Here are some practical tips:

• Stick to a regular sleep schedule
• Cut back on-screen time at night
• Use blue light filters on smart devices
• Try light therapy for shift workers

Disrupted sleep from night shifts or late-night screen time can harm health and may even raise cancer risk. By making simple changes in our lifestyle like limiting blue light and keeping a consistent sleep routine, we can support your body’s natural rhythms and healing. Let us take these steps to stay healthier and keep cancer risks at bay.

(Dr Priyanka Srivastava, Senior Consultant - Medical Oncology, Apollo Cancer Centre, Ahmedabad)