The term 'circadian' is derived from (Lain circa, around; dies, day), i.e., around 24 hours. All living beings have a cycle of physiological and biochemical processes, and behavioral patterns which are regulated by the 'biological master clock', the Suprachiasmatic Nucleus (SCN), below the hypothalamus. In man this cycle follows a circadian rhythm, which is a 24-hour cycle in time with sunrise and sunset (Day-night cycle). Signals transmitted by the SCN to the pineal gland suppress melatonin secretion during the day, and promote melatonin secretion during the night. Melatonin, also known as the sleep hormone, based on the light stimulus keeps us awake or asleep, depending on its level in the body.

Disruption of the circadian rhythm takes a heavy toll on our health, affecting many physiological parameters including blood pressure, heart rate,appetite, secretion of hormones, cell division, digestion, immune activity, DNA synthesis, rectal temperature, and sleep pattern.

Individuals more likely to suffer circadian rhythm disruption include shift workers, long and irregular duty hours, international jet travelers where time zones are crossed in a quick succession leading to disruption of the sleep pattern. This is known as Jet lag, or desynchronosis, and the symptoms are headache, fatigue, insomnia, loss of appetite, GIT disturbances, and dizziness. Even watching the TV or working on the computer for long hours can disrupt the circadian rhythm. Bright light also send conflicting signals to SCN, and suppresses melatonin secretion with resultant difficulty in falling asleep. (Ref: The Week - Health, Jan. 30, 2011). Drug therapy specially of the corticosteroids can been organized by basing it on the rhythms of the body, labelled as chronopharmacology, This has led to Alternate Day Therapy (ADT) with steroids.

A study reveals that one-fifth of the world's work-force works in night-shifts. Disruption in their rhythm makes them more prone to diabetes mellitus, mental depression and accidents. Another study reveals that suppression of melatonin secretion in women makes them more prone to suffer from breast cancer. Failure to synchronize our body functions like the sleep-wake cycle can be detrimental to our health in the long run. Circadian rhythm disruption can be detected by blood and saliva studies. Melatonin and Cortisol levels are important phase markers.

Treatment of Disruption

Detailed sleep-wake studies are done using sophisticated gadgetry, together with a detailed neurological evaluation by the doctor. The following measures may be adopted:

1. Light Therapy: It is employed to regulate the secretion of melatonin from the pineal gland.

2. Melatonin Tablets: May be prescribed to manage 'Jet lag' on medical advice.

3. Psychotherapy and Meditation.

Circadian rhythm disruption should not be taken lightly, as that may lead to serious systemic diseases. A regular health check-up is desirable.