Disrupted circadian rhythm could increase cancer risk


By prioritizing good sleep habits and working to keep our sleep-wake cycle in sync, we can lower our risk of lifestyle-related diseases

Our bodies are designed to operate in a 24-hour cycle that regulates various physiological processes, including sleep-wake cycles, hormonal regulation, body temperature, and eating habits. This natural cycle is known as the circadian rhythm, and when it is disrupted, it can lead to several health problems, including diabetes, obesity, depression, and cancer.

The suprachiasmatic nucleus, a part of our brain consisting of around 20,000 nerve cells, controls our sleep-wake cycle. This structure is guided by genes and other natural factors in our body and is also influenced by external factors. The most significant cue is light, which is directly linked to the sleep-wake cycle. Our bodies are designed to sleep when it’s dark outside and stay awake when it’s light.

The nerves that connect our eyes and the body’s master clock communicate with each other to regulate melatonin production, a hormone that makes us feel sleepy. When daylight fades, the eyes signal the brain to produce more melatonin, making us feel sleepy. When the sun rises, the signals tell the brain to turn down melatonin production.

Our personal circadian rhythm, also known as “chronotype,” determines how we feel with respect to our energies during specific parts of the day. This pattern varies from person to person and tends to run in families. People can fall into two categories: early birds or night owls. Early birds find it easy to wake up in the morning and have the most energy early in the day, while night owls find it hard to wake up in the mornings and are most energetic much later in the day.

Several factors can disrupt the circadian rhythm, including overnight shifts that go against the natural light and dark times of day, work shifts with erratic hours, travel that spans the course of one or more different time zones, a lifestyle that encourages late-night hours or early wake times, medications, stress, mental health conditions, poor sleep habits, and changes in the circadian rhythm before women’s period starts, causing poor sleep quality.


Several population and laboratory-based studies have linked circadian disruption to an increased risk of various types of cancer, including prostate, breast, colon, liver, pancreas, ovary, and lung cancer. The World Health Organization and the International Agency for Research on Cancer have designated circadian disruption as a likely carcinogen and classified “shift-work that involves circadian disruption” as potentially “carcinogenic to humans (Group 2A)” in 2007 and 2019.

Maintaining a healthy circadian rhythm is crucial to preventing several health issues, including cancer. Disrupting the sleep-wake cycle can lead to several health problems, and as such, we must prioritize maintaining good sleep habits. While factors such as work schedules and travel can sometimes make it challenging to stick to a sleep routine, we can still make an effort to stay active, avoid screens before bedtime, and maintain a comfortable sleeping space. By prioritizing good sleep habits and working to keep our circadian rhythm in sync, we can lower our risk of lifestyle-related diseases such as cancer and improve our overall health and well-being.

Also Read: Cannabis can improve cancer care

About the author

Dr Meenu Walia

Dr Meenu Walia, a leading cancer specialist, is the Director, Department of Medical Oncology and Hematology, Max Super Speciality Hospital in India. A Bharat Jyoti Awardee, she is the first DNB Medical Oncologist of India.

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