Day & Night Body Rhythm: How it controls my Health? HEF-IIC initiative on Environment and Health series

IIC- HEC series on ‘Environment and Health’

Day & Night Body Rhythm: How it controls my Health? 

at IIC, New Delhi under the aegis of

Health Environment Foundation India International Centre, New Delhi

The 17 May 2017 Panel discussion under the Health Environment Foundation (HEF) and India International Centre (IIC) initiative on Environment and Health Series was focused on Day & Night Body Rhythm: How it controls my Health? moderated by Dr. Naresh Gupta, Director-Professor, Maulana Azad Medical College, New Delhi and President, Health Environment Foundation. The other panelists included Professor AB Day, Head of Department of Geriatric Medicine, AIIMS, New Delhi; and Dr. TK Joshi, Occupational & Environmental Health Expert.
It emerged that:

Our Earth rotates one circle daily in nearly 24 hours (23 hour and 56 minutes) and is in synchronicity with our ‘habits’ of day & night rhythms, light & darkness, sleep & awake cycle, activity & rest cycles. It is not simply a matter of convenience, it actually rests on body and cosmic signals that will continue to act on our human body even if day/ night pattern is altered artificially. Thus these rhythms are endogenous into our body system. It shows up prominently when one air travels across the different time zones- ‘jet lag’ is sl well recognised. What is not usually appreciated is it can affect our health, growth and repair mechanisms in many ways. It is known as the Circadian (from Latin circa meaning “about” and dies meaning “a day”) Rhythms, under a new science called Chronobiology.


Though it was observed in plant behaviour for long time, its dedicated study in animals is rather recent beginning with identification of its regulating genes in Drosophila melanogaster in 1971. Interestingly, these genes were named “period gene”, “clock gene”, “cycle gene” etc. Mutations in the equivalent genes in humans is known to produce an ‘advanced sleep phase disorder”  (ASPD), in which patients feel very sleepy early in the evenings (6:00–8:00 pm) and wake up early in morning around 3:00 am. Thus our day & night rhythm are genetically controlled.


Some of this control is mediated through body hormones esp. Melatonin, secreted by the pineal gland in the brain. It is often equated with the Third-Eye referred to in Indian mythology and spirituality. Another noteworthy feature is the presence of this biological circadian rhythm in across the body cells. The ‘Master Biological Clock’ to monitor and coordinate this activity resides in the suprachiasmatic nucleus (SCN) which contains about 20,000 nerve cells. It is located in the hypothalamus of the brain, close to the optic nerves coming from the eyes cross. This may also explain the dependence of this hormonal control of ‘Day & Night Rhythm’ on the light signals gaining entry through the eye! Recently some specialised mediating cells melanopsin have been identified in the retina.


Thus Circadian Rhythms go with

  • Physical
  • Mental and
  • Behavioural

changes that follow a roughly 24-hour cycle, responding primarily to light and darkness. These sustain through body temperature variations. Further these are endogenous and entrainable meaning it is possible to reset in response to external stimuli. External factors such as

  • Exercise
  • Hormones
  • Medications

can affect these rhythms.


DAY & NIGHT RHYTHMS show up their influence in our everyday life. The widespread ‘Call- Centres’ culture, employing thousands of people are a prime example. So also the traditional ‘Shift Workers.‘We know the biological effects of such working hours and only learning to minimize their health impact be regulating the work hours. Any changing work schedules keep them from setting a sleep patterns, affecting their health, and may face symptoms such as:

  • Insomnia
  • Daytime sleepiness
  • Indigestion
  • Irritability


The Shift Workers may benefit from the following:

  • Delay going to bed and wake up by one to two hours on the last few days of an evening shift.
  • As the night shift begins, this will help adapt to the new schedule.
  • Allow extra time to adjust to a new work schedule.
  • Do not skip on time for sleeping.


Pilots face symptoms similar to Shift Workers, while crossing through several time-zones and regions of sunlight & darkness in one day, and may spend many hours awake both day and night. It adds too fatigue and may make the circumstances accident prone.


Also, bear in mind the Normal Sleep hours for an adult are 7-9 hours. The babies sleep much more, 20-22 hours in a day. The sleeping time is when their growth occurs. And the reparative processes of the body are also more active during sleep.

Melatonin is a pro-sleep hormone secreted by the pineal gland in the briain, and makes one sleepy as the sunlight goes out and and awake as the morning rays hit your retina cells in the eyes.

For the geriatric population,  healthy sleep is even more important. Even octogenarians need 5-6 hours sleep. It is restorattive, and its lack correlates with mental health problems.



  • Never miss sleep
  • Sleeping hours must coordinate with circadian rhythm
  • Aways sleep in darkness- the presence of light will disrupt the circadian rhythm and the biological clock
  • Power naps are indeed useful


JET LAG is faced by long-distance flight passengers, who also travel across different time zones and different light/ day timings. One starts off during day and arrives in broad daylight after 12 hours! All this disrupts the circadian rhythms, producing a sleep disorder. Waking up early mornings, and sleepy during evenings! Compare APSD above.


A ‘Social Jet Lag’ can be created from artificial and forced disturbance in sleep rhythms from stressful commitments at work, school or social needs.


The Jet Lag sleep disorders may benefit from oral intake of Melatonin tablets.


There are other hormones such as the corticosteroids affected in the circadian rhythm. And it is believed that increasing prevalence of Obesity and Diabetes mellitus may be related to misalignment of this circadian rhythm.

Its relationship with Drug Abuse is also a matter of scientific research.


Will this circadian biological rhythm also influence the effects/ toxicity of medical treatments offered to patients dependent on the time of its administration during the 24-hour day? The speciality of Chronotherapeutics looks into it. Some practice of this may be seen in traditional systems of treatment.


In summary, the Circadian Rhythms / Day & Night Rhythms are produced by natural factors within the body and regulated by the master internal  Biological Clock , for the benefit and health of our body. Light is a main player, the hormones its effectors. Progress and civilisation is disrupting some of it, producing many health effects- some well understood and we are beginning to unravel. The science of Chronobiology is indeed very new!



Interesting comments/ issues from audience participation:

  • Medicine- induced sleep
  • Achieving totally-dark darkrooms for best benefits of sleep may not be easy in our scenario; besides making it ‘unsafe’ for the elderly population
  • Large individual variations in sleep requirements
  • Daytime power naps are useful
  • Does exercise affect sleep requirement?
  • Does meditation affect it too
  • What if studying late nigh is good for me,,,?
  • Which is better- A walk in the evening or in the morning?
  • Whether the EMF, the non-ionising electromagnetic frequency emissions, in case of mobile phones and mobile towers also exert affect through pineal gland thereby disrupting circadian rhythm         (please our earlier post on Mobile phones and Mobile towers on health)


Best Regards!


Naresh Gupta, M.D.

Health Environment Foundation

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