Circadian Rhythms

Your body’s natural and internal smartwatches

When you were a baby, how did you know when to sleep or when to wake up for feeding time? Answer? A growling stomach. Partly, yes, but your circadian rhythm which serves as an internal clock, also plays a huge part in that even when you were just a baby.

What is a circadian rhythm?

Your circadian rhythm is a natural endogenous (internal) process that tells your mind and body to sleep and then wake up. It (the rhythm) repeats itself approximately every 24 hours.

The word circadian comes from the Latin phrase “circa diem”, which means “about a day”, hence the 24 hours. So, in about a day, you have various circadian rhythms happening inside your body like mental, physical, and behavioural changes or processes. These processes include your appetite, hormone levels, energy levels and alertness, body temperature, blood pressure, and the most noticeable, your sleep/wake cycle. You’re sleepy at night and awake during the day. You’ll also be surprised to know that other living organisms like other animals, plants, and even microorganisms like bacteria and fungi have circadian rhythms. A special branch of biology called chronobiology, studies your circadian rhythm.

What controls your circadian rhythms?

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Among mammals (including us), the circadian rhythms are regulated by a group of specialised cells called suprachiasmatic nuclei in an area of the brain called the hypothalamus. This group of cells is called the master clock and sets the tone of your circadian rhythms. The hypothalamus links your nervous system to your endocrine system. It plays an essential role in modulating your body temperature, thirst, appetite, weight, sex drive, blood pressure, emotions, and of course, sleep cycles.

Say goodnight with Melatonin

Your pineal gland, a valued member of your endocrine system, resides near your hypothalamus and is responsible for the production and secretion of the hormone melatonin (also called the sleep hormone). Melatonin levels start to rise around 2 hours before your regular bedtime. It reaches maximum levels in your blood between 3 to 4 am.

Melatonin helps normalise your circadian rhythm and prepares your mind and body to go to sleep. If you’re exposed to artificial light at night (like late-night movie marathons), the release of melatonin may be blocked, and you can have trouble sleeping. If you want to increase melatonin secretion, turn off the lights.
A 2018 research study published in the British Journal of Pharmacology found that melatonin treatment among volunteers with circadian rhythm-related disorders led to clinically meaningful positive effects. This treatment can be extended to people with jet lag and those with shifting schedules. Exogenous melatonin administration may help them normalise their circadian rhythms. If you’re having trouble falling asleep, melatonin supplements may help. Ask your primary healthcare provider first before taking them.

What external and internal factors affect circadian rhythms?

Although your circadian rhythms are regulated by the specialised cells in your hypothalamus, some external and internal factors affect them. External factors include:

Artificial light. That artificial light coming from your mobile phone can disrupt your circadian rhythms.
Noise
Medications
Diet. Drinking lots of caffeine-containing drinks or other stimulants can delay sleep onset.
Exercise
Hormone levels
Work schedules
Daylight savings time. You may have adjusted the time on your watch, but your body didn’t physiologically go along with it.
Ambient temperature

On the other hand, internal factors like body temperature, illness, and stress can affect your circadian rhythms.

Negative health consequences of disrupted or abnormal circadian rhythms

Who here likes jetlag? Nobody. It’s like the world’s worst hangover without the good and hilarious times leading to it. Pilots, flight attendants, and airline passengers who cross different time zones may experience jet lag, a negative effect of a disrupted circadian rhythm.
Jet lag is a type of circadian rhythm sleep disorder. People with jet lag may experience the following:
1. Insomnia, too much sleepiness, or waking up too early.
2. A general sense of not feeling well. You feel tired most of the day.
3. Hard or soft? Jet lag may cause constipation or diarrhoea.
4. You have difficulty concentrating and paying attention.
The symptoms commonly appear within a day or two from your date of arrival after you’ve travelled across two or more time zones. They last longer the more time zones you cross. Crossing time zones disrupts your circadian rhythms and puts them out of sync from the country or zone you came from.
Flight attendants have it easy compared to astronauts at the International Space Station (ISS) The astronauts experience night-time 16 times a day at 45-minute intervals while orbiting the Earth every 90 minutes. Those guys have some really messed up circadian rhythms. Shift workers also fall victim to disrupted circadian rhythms and may experience the same symptoms as flight attendants.
Your eating patterns also help regulate your circadian rhythms. Irregular eating patterns desynchronize when and how your body handles the regulation of glucose and energy homeostasis from the food you eat. Your body will have a hard time managing what to do with the excess nutrients and energy leading to an imbalance. Alterations in your feeding patterns lead to weight gain and the development of type 2 diabetes mellitus and cardiovascular diseases.
A 2014 research study published in the American Journal of Physiology stated that high fat and high sugar diets might have indirect negative effects on the suprachiasmatic nuclei in your hypothalamus and disrupt your circadian rhythm.

How do we reset or keep healthy circadian rhythms?

Our circadian rhythms are there to protect us. They give you vital clues that it’s time to rest and recuperate or stay wide awake and alert during your work. You must understand your circadian rhythms and know how to take good care of them. Below are some practical tips:

Alcohol, smoking, and caffeine-containing drinks should not be consumed right before you go to bed.
A power nap after lunch should maintain your energy levels and alertness for the rest of your day.
Mobilise! Walk around your work area once in a while. Wear a Fitbit watch (or any fitness smartwatch) that vibrates to remind you to get up and move.
Dim the lights or better yet, turn them off when you’re about to sleep. Cut gadget time by half.
Shift workers on night shift may work to a maximum of five days or less, with two days off or more. As much as possible, don’t extend your working hours. Try cutting travelling time from your home to your job. Lastly, stay away from working shifts that rotate frequently.

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Air travellers who cross multiple time zones should stay hydrated with water (not with alcohol or coffee) and quickly adjust your bedtime when you arrive at your destination. Go to sleep when it’s time to go to bed at your new time zone. Fight the urge to sleep until it’s the right time. Wake yourself up by exposing yourself to sunlight and warmer temperatures.

Remember, your circadian rhythms are composed of different behavioural, physical, and mental processes, not just your sleep/wake cycle. They are present to protect your body. Pay attention to what they’re trying to tell you. You’ll function optimally every day when all your circadian rhythms are keeping up pace with each other. It’s like the clocks in your house. You want them to be in sync with each other and to tell the correct time.