What is the Circadian Rhythm?

What is the circadian rhythm?

You’ve probably heard the term before. In fact, you’ve probably heard it used interchangeably with similar terms including the circadian clock, body clock, and sleep-wake cycle.

The circadian rhythm is the body’s natural regulator of sleeping patterns. Over a period of 24 hours, the cycle occurs once. Your body clock controls how much melatonin is released into your body.

In a regular cycle, melatonin levels will begin to rise in the evening, peak overnight, and then will start to drop in the early morning.

How melatonin affects your body clock

Melatonin is a hormone produced in the pineal gland, a small gland located in the brain. Natural melatonin is the hormone that regulates sleeping patterns, effectively, telling your body when it is time to go to sleep or time to get up.

Darkness causes the body to produce melatonin, which signals the body to prepare for sleep, regulating your body clock.

That is why you’re advised to sleep in a darkened room, free from artificial “blue light” produced by televisions, clock radio lights, night-lights and, of course, smartphones.

Melatonin production is hardly detectable during the day when the body is exposed to light.

How does light and dark influence your circadian rhythm?

When day turns to night and the world starts getting darker, your body’s melatonin production kicks in.

This happens every night, and is a signal to your body that you’re winding down for the day and are almost ready for sleep.

Daylight saving and the changing seasons can confuse your rhythm slightly, which can make falling asleep a little bit harder.

As you get older, natural melatonin production starts to diminish. That is often why some older people can function on fewer hours of sleep compared to teenagers or young adults, while others might struggle to get to sleep at night.

Circadian rhythm disorder

Your circadian rhythm might be disrupted if you find it hard to go to sleep at night and wake up in the morning in sync with regular work, school, and social needs.

A circadian rhythm disorder does not necessarily mean you suffer from poor quality sleep; rather, it could be that the body’s natural sleep-wake rhythm is abnormal.

Shift workers and those that travel across time zones often are most likely to suffer from circadian disorders.

In a recent study*, Monash and Harvard researchers used Optalert’s technology to measure the drowsiness of shift workers under different conditions.  The subjects of this experiment had the phase of their circadian rhythm determined by measuring their melatonin levels. Their alertness/drowsiness was significantly affected by misalignment of their circadian rhythms, and Optalert’s JDS scores reflected the subject’s alertness/drowsiness state well.

* “Ocular measures of sleepiness are increased in night shift workers undergoing night shift near the peak time of the 6-sulfatoxymelatonin rhythm.”  Ftouni S, Sletten TL, Nicholas CL, Kennaway DJ, Lockley SW, Rajaratnam SMW.Journal of Clinical Sleep Medicine, 2015;11 (10): 1131-1141A”

Jet lag can wreak havoc on your body clock

If you’ve ever travelled between two drastic time zones, say, between Melbourne and New York, you’re probably familiar with the tip to set your watch to your destination’s time as soon as you board the plane, or even prior, with the aim of settling into your future time zone and decreasing the effects of jet lag.

Getting used to a new time zone isn’t always easy, and an out-of-sync circadian rhythm doesn’t help!

The circadian rhythm is thrown when you travel between drastic time zone changes and you are trying to remain awake and alert during a time when you would normally be asleep.

Our own James Gorry recorded a High Risk warning of drowsiness after travelling from Melbourne to Los Angeles a few years ago.

Shift work affects a natural sleep-wake cycle

Shift workers are some of the individuals most at risk of the effects of a disrupted circadian rhythm.

Demanding hours, outside the regular sleep-wake cycle, force us to work throughout times where we’d normally be asleep.

Not only must shift workers adjust to their new sleep-wake cycle, but they must also ensure they are getting quality sleep during their rest periods, and remain vigilant at work in order to perform tasks properly and safely.

This is why shift work is one of the most demanding jobs.

Sleep regulation is truly fascinating. Those struggling to sleep at night, sometimes take a melatonin supplement. As always, consult your doctor if you are having trouble sleeping.