As autumn settles in and the nights grow longer, it’s hard to ignore the impact the decrease in daylight has on our energy, sleep and overall mood.

Many of us know this to be the result of a disruption to our circadian rhythm – the 24-hour body clock which controls everything from when we wake up in the morning to our body temperature and metabolism. But did you know that this circadian cycle isn’t the only type of biological rhythm out there?

A phrase used to describe biological processes which occur repeatedly over a set time, biological rhythms can be found across the natural world, although you’ll find plenty at work within your own body. 

While chronobiologists – experts who study biological rhythms – look at a wide range of these cycles, there are four main ‘types’ which are found in humans. 

While our circadian rhythm may be the most widely known biological rhythm, there are a total of four key biological rhythms which influence how our body functions:

• Circadian rhythms: biological changes which take place over a 24-hour period, driven by the suprachiasmatic nucleus (SCN) in the brain (eg changes in metabolism throughout the day)
• Diurnal rhythms: a type of circadian rhythm synced with day and night (eg the sleep-wake cycle)
• Ultradian rhythms: biological changes which occur at a higher frequency than circadian rhythms (eg surges in appetite)
• Infradian rhythms: cycles that last longer than 24 hours (eg the menstrual cycle)

Other types of biological rhythms include circatidal rhythms – those with a period of 12.4 hours influenced by the tides, often found in marine creatures such as crabs and molluscs – and circannual rhythms – 12-month cycles influenced by the change in seasons, like the leaves on the trees. 

Some human examples of circannual rhythms have been found in the past, but we tend to be less affected by the seasons than other creatures.  

You might know more about your circadian rhythm, but that doesn’t mean it’s the most important. According to Sebnem Unluisler, a genetic engineer at the London Regenerative Institute, each rhythm plays a distinct, important role

“Each biological rhythm serves its own vital purpose,” she says. “They are essential for health, the overall functioning of organisms and for survival. 

“Biological rhythms enable synchronisation with the environment, such as aligning sleep-wake cycles with the natural daylight cycles and rhythmic patterns which help with energy conservation. Disruptions to the biological rhythms can be hugely detrimental to physical and mental health.”

Indeed, as Unluisler points out, the disruption of our biological rhythms – often referred to as biological rhythm disorders – can cause several issues such as anxiety, daytime sleepiness and reduced mental alertness. 

Just look at the mountains of research into the detrimental impact of working night shifts; we know working against the natural wake-sleep cycle can lead to increased risk of conditions such as heart disease, diabetes and strokes. 

Our biological rhythms tend to be self-sufficient – you just want to make sure you avoid doing things which could disrupt them from getting on with things in the background. Below are just a few tips for supporting each type of biological rhythm.

1. Embrace light exposure for your circadian and diurnal rhythms

Because diurnal rhythms are a type of circadian rhythm, adopting circadian-friendly habits will support both. These are the kinds of habits you might turn to when trying to improve your sleep, such as going to bed and waking up at the same time.

Others are more to do with your environment. “Spend time outdoors during the daylight hours and enjoy exposure to natural light to support the internal body clock,” Unluisler recommends. “Minimising the time that you spend on screens and your exposure to artificial light – both of which can be disruptive to the sleep hormone melatonin – can also help.”

2. Get stress under control to regulate your ultradian rhythm

There are so many examples of ultradian rhythms in the body – our sleep cycles, brain activity and blood circulation are just three – so there is no one way to support all your ultradian rhythms. Instead, you can focus on managing any sources of disruption. 

Managing your stress levels is particularly important as this can be disruptive to many of our ultradian rhythms, Unluisler says. “Try to take short, regular breaks during work to recharge and practice relaxation techniques such as deep breathing or mindfulness.”

3. Focus on eating a balanced diet for your infradian rhythm

While there are a handful of infradian rhythms found within the body (our hair growth cycles being one of them), the most significant is the menstrual cycle. To support this cycle, Unluisler suggests adopting healthy lifestyle habits including regular exercise (both cardio and weight-bearing) and maintaining a balanced diet.

“Drinking plenty of water and managing your stress levels to support overall health can positively influence infradian rhythms such as the menstrual cycle,” she adds. 

Images: Getty