Circadian Rhythm

Circadian rhythm (also known as your sleep/wake cycle or body clock) is a natural, internal system that's designed to regulate feelings of sleepiness and wakefulness over a 24-hour period. 

How does it work?

A part of your hypothalamus (a portion of your brain) controls your circadian rhythm. That said, outside factors like lightness and darkness can also impact it. When it’s dark at night, your eyes send a signal to the hypothalamus that it’s time to feel tired. Your brain, in turn, sends a signal to your body to release melatonin, which makes your body tired. That’s why your circadian rhythm tends to coincide with the cycle of daytime and nighttime. 

Role of Circadian rhythm

  • Circadian rhythms can influence sleep-wake cycles, hormone release, eating habits and digestion, body temperature, and other important bodily functions.
  • Many hormones and immune signals are produced rhythmically in 24-hour cycles.  Cortisol, for example, which is known to suppress inflammation and regulate certain T cell–mediated immune responses, peaks early in the morning and ebbs as the day progresses.
  • Across diseases, from cancer and cardiac ailments to allergies and arthritis, epidemiological data and clinical trials are revealing that timing medications to the body’s internal clock could improve their effectiveness and reduce side effects.

Ayurvedic perspective 

Ayurveda believes that an early start is best for your body. Called the “brahma muhurtha,” the time to set your alarm clock is exactly 1 hour and 36 minutes before sunrise. The body’s biological clock is regulated by the doshas.   

  • Kapha: The time of maximum activity of kapha is during morning and evening from about 6 to 10 a.m. and 6 to 10 p.m.
  • Pitta: this period is during midday and midnight, from about 10 a.m. to 2 p.m. and 10 p.m. to 2 a.m
  • Vata hours are dawn and dusk, from about 2 to 6 a.m. and p.m.

What disrupts the circadian rhythm?

  • Travelling through different time zones leading to jet lag
  • Night shift work
  • Sleeping very late watching TV or reading or late night partying, late night meetings due to different time zones and so on. 

Biological clocks that run fast or slow can result in disrupted or abnormal circadian rhythms. Irregular rhythms have been linked to various chronic health conditions, such as sleep disorders, obesity, diabetes, depression, bipolar disorder, and seasonal affective disorder.  This explains why shift workers are more prone to gastrointestinal problems such as constipation, diarrhoea, or gastric ulcers. Hence it is important to have proper schedule for sleeping and waking up daily even on weekends.   

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