What is the difference between a biorhythm, a circadian rhythm and a body clock?
A biorhythm is simply any type of predictable cycle in a living organism. Some of these are well-known, like the circadian rhythm, which governs our sleep-wake phases. Circadian rhythms are found in most living things, including animals, plants, and many tiny microbes. Within this rhythm are physical, mental and behavioural changes that follow roughly a daily pattern. The term originates from Latin and literally means approximately (circa) daily (diem). Your circadian rhythm influences your sleep-wake cycle, daily patterns of alertness, mood and performance, hormones (such as melatonin and cortisol), and many other processes including digestion, heart rate, body temperature and lung function.
The circadian rhythm is often referred to as our body clock because it is the body’s innate timing device. This natural internal clock is affected by environmental cues, primarily light (but also temperature). Your body clock causes you to feel more energetic and alert during certain times of the day and more lethargic and run down at other periods of the day. All humans have circadian rhythms, but there are slight differences in the length of the cycles, which is one of the reasons some people are ‘night owls’ and others are ‘morning people’.
Our circadian rhythm is managed by a part of the brain called the Suprachiasmatic Nucleus (SCN). Light travels to the SCN from the eye signalling that it is time to be awake. The SCN then triggers other parts of the brain that control hormones, body temperature and other functions that play a role in making us feel sleepy or awake.
An example of a human body clock
Why are circadian rhythms important?
When a person’s circadian rhythm is disrupted, sleeping and eating patterns can run amok. Looking after your body clock will help prevent and help treat sleeping disorders and benefit your overall health. Irregular rhythms have been linked to several health problems, including obesity, diabetes, high blood pressure and cardiovascular disease. As well as contributing to mental health issues, such as depression, bipolar disorder and seasonal affective disorder. Recent research has connected circadian rhythm disruption to Alzheimer’s disease, Parkinson’s disease, and Huntington’s disease, and autism spectrum disorder.
Even seemly small changes, like the beginning and end of Daylight Savings can disrupt our body clock. Statisticians have found there are more traffic accidents and workplace injuries when we move the clock forward and lose an hour of sleep. Furthermore, heart patients are at greater risk of myocardial infarction in the week following the Daylight Savings time shift.
Jet lag and shift work
A change in the environmental light-dark cycles can speed up, slow down, or reset circadian rhythms. This is why jet lag confuses our bodies. Symptoms of jet lag should only last a few days and can include headaches, lethargy, irritability and reduced cognitive function.
Shift workers can experience a similar problem because the daily cues for the circadian rhythm do not match up with when a person is asleep and awake. This may lead to issues with sleep or other aspects of the worker’s health.
What can you do to preserve your circadian rhythm?
Keeping your body’s daily cycle balanced and steady may be one of the most positive things you can do for your overall health, so here are some actionable tips to keep yours on track.
1. The best way you can support your natural circadian rhythm is to keep a routine according to the Sleep Health Foundation. As much as possible, go to bed at the same time and wake up at the same time every day. Unfortunately, this also means ditching your Sunday sleep in.
2. Avoid artificial light after sundown. The light emitted from our computers, phones, TVs, and even fluorescent light bulbs can interfere with our body clocks by tricking the body into thinking it is daytime. Try dimming the lights in the evening and having a technology free period before bed. Professor Lockley from the Alertness CRC suggests making your sleep space as dark as possible or using an eye mask.
3. Get as much natural light as you can during the day, particularly in the morning. Open the windows, eat lunch outside, go for a short walk, take the window seat on the train or work outside.
4. Physical activity is another cue for your body clock that it is time to be awake. So, get your large joints moving in the morning with some exercises or stretches.
5. Dr Felino Cagampang from the University of Southampton reported that digestion and metabolism play a role in maintaining your circadian rhythm. He says that ideally, we should be eating during daylight and fasting when it is dark outside. This won’t always be practical but maybe you could consider an earlier dinner. He also recommends making breakfast the biggest and most nutritional meal of the day.
6. Certain foods that send conflicting cues to your body clock are best avoided in the afternoon and evening. These include caffeinated drinks, alcohol, foods high in saturated fats, and sugary food or drinks.
7. Finally, get enough sleep to keep your circadian rhythm in check. For most adults this is at least 7 hours of sleep.
Recommended sleep chart from the National Sleep Foundation
Tips for resetting your body clock
Sometimes life gets in the way and our body clocks fall out of sync, due to travel, work, stress, children, social commitments, illness or other factors. Here are a few ways to reset your body clock when it has gone off course.
• Take the family camping. This is the perfect way to get plenty of light during the day and minimal artificial light at night. If you take a mobile phone, save it for emergencies.
• Make gradual changes until you have your groove back. Research suggests adjusting your current sleep schedule by no more than 30 minutes per day and remain on that schedule for a few days or even weeks, so your body catches up. For instance, if you are in the habit of going to sleep at 2am, try 1:30am for a week and after that bring it forward to 1am.
• If you are recovering from jet lag, try this free app which calculates the best times to be exposed to light and darkness to get back on track.