Circadian rhythms are physical, mental, and behavioral changes that follow a 24-hour cycle. Light and dark are the primary stimuli for these natural processes, affecting most living organisms, including microorganisms, plants, and animals. Chronobiology is the study of these rhythms. Sleeping at night and remaining awake during the day is a well-known example. The suprachiasmatic nucleus (SCN), a small area in the brain's hypothalamus, regulates our circadian cycles. The eyes provide direct input to the SCN, which aids in controlling sleep-wake cycles in response to light exposure.

Can Cancer or Cancer Treatment Affect Sleep?

Cancer and its treatments can significantly disrupt sleep. Anxiety, pain, or radiation and chemotherapy side effects can all cause insomnia or poor sleep, which lowers a patient's general quality of life. Because of the physical and mental changes brought on by the cancer, survivors may continue to have sleep issues long after therapy is over.

Restoring Circadian Rhythm for Better Recovery

• Stick to a Consistent Sleep Schedule: Be consistent with your sleeping and waking times. Our circadian rhythm likes routine and consistency. Aim to go to bed around the same time and wake at the same time every day, even on weekends.
• Avoid Blue Light at Night: Artificial blue light emitted from phone, tablet, and laptop screens can disrupt your internal body clock by tricking the brain into thinking it's daytime and inhibiting the release of melatonin. As a result, late-night screen use has been found to keep you more alert and energized, making it harder to fall asleep.
• Get Morning Sunlight: Morning exposure to natural light helps reset your internal clock by increasing the wakefulness hormone cortisol and decreasing melatonin. 
• Limit Evening Caffeine: Caffeine can significantly interfere with your circadian rhythm if consumed too late in the day. This is because it can take around 6-7 hours for its effects to wear off.  One study found that drinking coffee 6 hours before bedtime can have disruptive effects on sleep. So, if you enjoy coffee, make sure you drink it before noon.
• Maintain Regular Meal Times: Eating at consistent times helps manage appetite and digestion cycles. Irregular meal timing can change your circadian rhythm, making you feel alert or exhausted at unusual hours.
• Avoid Late-Night Exercise: Proper exercise can improve sleep quality and duration, while a healthy sleep-wake cycle ensures more strength and endurance when you work out. However, exercise is also stimulating if you work out too close to bedtime. 

A well-regulated circadian rhythm is essential for overall health, especially for cancer patients and survivors. Establishing appropriate sleep habits can decrease long-term health risks, boost recovery, and improve treatment outcomes. Making sleep a priority gives your body the best opportunity to recover and flourish, not just to relax.