Get to know your body’s biological clock and improve your sleeping habits.

What are circadian rhythms? How can you maintain a healthy one? What happens if you don’t? To explore more, read on...

1. Think of circadian rhythm as your body’s biological clock

We can thank our circadian rhythm for making us feel tired at certain times of the day and energised at others. Although external cues, such as exposure to light and daily schedules play a part, tiredness is largely decided by our built-in biological cycle. This even accounts for the mid-afternoon energy lull that many of us experience after lunch. The 24-hour natural rhythm has also been observed in plants and animals.

2. It’s about balance and cycles

Our circadian rhythm basically tells us to sleep and rise on a 24-hour recurring cycle. But the complete picture is a little more complicated. Circadian rhythms interact with something called a ‘sleep-wake homeostat’. This takes the amount of sleep you’ve recently had into account and attempts to redress the balance regardless of your cycle: it’s what makes us feel tired in the middle of a day after a sleepless night. Keeping your homeostat and circadian rhythm in sync helps achieve the best night’s sleep.

3. Seasons play a massive part

Of all the external factors that affect circadian rhythms, sunlight is the most important. Changing the clocks forward and backward to see in new seasons can have a disruptive impact on energy levels. Waking up to dark mornings and trying to sleep during bright evenings produces hormones that make waking and sleeping more difficult. People who are most sensitive to sunlight can experience mild to moderate depression known as seasonal affective disorder (SAD) in winter.

4. Age and eating habits impact our sleeping pattern

As we age, we produce fewer growth hormones and our slow-wave, or deep sleep, declines. Aging eyes can also disrupt circadian rhythms, as eyesight worsens and light hitting the retina is reduced. This is often the reason blind people can suffer from sleeping disorders. A 2019 study confirmed that eating habits can also disrupt our sleep cycle. The hormone insulin, released when we eat, impacts our rhythm and can prevent us from falling asleep.

5. Circadian rhythm disorders have serious implications

Many of us will have been out of sync with our circadian rhythm through jet lag or shift work. It’s important to address the problem quickly as going about your daily business out of sync over an extended period of time can have a serious impact on health. A 2014 study found that cardiovascular disease, diabetes, obesity and psychiatric conditions are all profoundly affected by circadian rhythms. However, it’s still not understood how sleep disorders contribute to our risk of disease.