By Jack Harley, MSc, University of Oxford
We all know getting quality sleep is important, but it’s not the full story. It is possible to get 8 hours of sleep, and still feel groggy in the morning. In this case, you may have neglected to take care of your circadian rhythm. Fortunately, you can get your circadian rhythm back on track by following a few simple daily habits.
Table of Contents
What is circadian rhythm?
Circadian rhythm refers to the body’s internal processes that maintain the sleep-wake cycle. They encompass physical and psychological changes that occur over a 24-hour period. Circadian rhythms cause our bodies to be active during the day, and restful at night. If you have ever had jet lag, you will know how persistent circadian rhythms can be.
As well as controlling the sleep/wake cycle, circadian rhythm also influences a range of other biological factors such:
- Arousal and drowsiness
- Energy levels
- Stress hormone levels
- Health and risk of disease
How does circadian rhythm work?
Inside every cell in the body are molecular clocks that tick away in an established rhythm. These internal clocks are synchronized by a master clock in a part of the brain called the suprachiasmatic nucleus (SCN).
This clock responds to environmental signals to tell the time, the most important of which is light. When light enters our eyes, it signals to the master clock that it is day or night. In the morning, this light results in the body producing cortisol, making us feel alert and awake. At night, the pineal gland produces melatonin, which reduces wakefulness and makes us feel sleepy.
The master clock is also influenced by other environmental cues such as food intake, movement, exercise and temperature.
Why is circadian rhythm important?
Circadian rhythm is essential for health and wellbeing. It is also important for feeling focused and energized during the day. If you often experience daytime sleepiness, or difficulty falling asleep at night, it may be a sign that your circadian rhythm is off.
A misaligned circadian rhythm over a long period of time may be associated with a range of health conditions such as:
A poor circadian rhythm is also linked to psychiatric conditions such as depression and bipolar disorder, as well as neurodegenerative diseases like dementia.
However, a properly aligned circadian rhythm is associated with improved sleep quality and reduced risk of adverse health effects. Circadian rhythm is also associated with improved measures of cognitive function including attention, learning ability, and working memory. This may result in higher productivity during the day.
What factors affect circadian rhythm?
Circadian rhythms can be altered by many common aspects of our modern lifestyle.
For example, if we go to bed at 10 pm one day, and 2 am the next, our internal body clocks become confused. This can make it harder to fall asleep, reducing the quality of our sleep and throwing off our circadian rhythm.
Several environmental cues, known as ‘zeitgebers’, can influence our circadian rhythm. These include:
- Sleep timing and duration
- Light exposure
- Food consumption and timing
- Movement and exercise
Unfortunately, many common habits and routines may disrupt our circadian rhythm. These include:
- Shift work
- Eating late at night
- Exposure to bright lights at night, for example from a phone or laptop
- Changing time zones when flying to another country
- Sleeping at different times each day
Fortunately, it is often possible to restore a healthy circadian rhythm by following a few simple daily habits.
The ideal circadian day
In a perfect world, you would go to bed when it is dark and wake up when the sun rises, so your sleeping pattern would match that of the sun. This would ensure an optimal circadian rhythm.
However, due to work, family and other obligations, it is often hard to follow the ‘early sleep, early wake’ philosophy. Even so, we can still establish a realistic circadian day that is compatible with our daily schedule, by following six daily habits listed below.
1. Go to bed at a consistent time
In order to maintain a healthy circadian rhythm, it is important to follow a regular sleep schedule. Sleeping at the same time each night and getting consistent amounts of sleep can help establish this habit.
You should go to sleep at a time that allows you to get the recommended amount of sleep, which is 7 hours for most adults. For example, if you need to wake up at 7 a.m. for work, you should be in bed ready to sleep at 12 a.m.
Try to choose a sleep schedule that you can maintain every day, including weekends and holidays. Sleeping in on weekends may be tempting, but doing so may disrupt your circadian rhythm and make it difficult to get back to a consistent routine.
It is also important to wake up at the same time every day. However, if you go to sleep at the same time and sleep for a consistent duration, this should happen automatically.
2. Wait at least 1 hour after waking up before eating
Try to avoid eating as soon as you wake up, and instead. Instead, wait at least 1 hour before eating your first meal. This will extend the overnight period of fasting, allowing your circadian rhythm to reset.
Waiting 1 hour or more to eat breakfast can also make it easier to follow a time-restricted eating pattern. Time-restricted eating involves consuming all of the food for the day within a period of between 12 to 16 hours. This fasting period helps to improve your circadian rhythm, and may also promote weight loss, help treat type 2 diabetes and improve metabolic function.
3. Eat breakfast at a consistent time
The timing of breakfast can send a signal to the body’s internal clock about the time of day. Changing the time you eat your first meal regularly can confuse the body’s internal clock and disrupt the circadian rhythm.
Therefore, try and eat breakfast at a similar time each day. For example, if you wake up at 7 a.m., you may wish to eat breakfast at 8 a.m. or 8.30 a.m. daily.
4. Eat your last meal 2-3 hours before bed
Try to leave at least 2-3 hours between when you eat your last mouthful of food and when you intend to sleep. Eating too close to bedtime can disturb the quality of your sleep, and disrupt your circadian rhythm.
In addition, eating your last meal at least 2-3 hours before bed makes it easier to follow a time-restricted eating schedule, which helps to maintain a healthy circadian rhythm.
While you are avoiding food in the late evening, try to also avoid exposure to bright lights. Light, particularly blue lights emitted from electronic devices may signal our circadian rhythm that it is daytime. Try to avoid using a phone or laptop too close to bedtime, and dim the lights to help prepare your mind for sleep.
5. Get at least 30 minutes of bright light during the day
Light is the most important trigger for circadian rhythm. Therefore, try and go outside for at least 30 minutes in the morning and expose yourself to daylight. Doing so sends a signal to the brain that it is time to wake up and helps to reset your circadian clock.
It is important to go outdoors if possible, as the amount of sunlight outside is vastly more than that inside, even when the lights are switched on. On a cloudy day, you may receive more than 100,000 lux (a measurement unit of light) outdoors, compared to only 100 lux indoors.
To expose yourself to bright lights in the morning, you could try the following:
- Eating your breakfast or drink coffee outside, e.g. on your front porch
- Eating your breakfast near a well-lit window
- Riding a bicycle to work instead of driving
- Going for a walk or run in the morning
Alternatively, if none of the above are convenient, you can buy a special light box that emits blue light and use it to increase your morning light exposure.
6. Exercise for at least 30 minutes per day
Exercise and sleep support each other in a mutually beneficial way. Regular exercise promotes deeper and more restorative sleep, which in turn allows for more energy the following day to exercise. Both of these factors help to establish a healthy circadian rhythm.
However, it is best to avoid exercising 1-2 hours before bedtime, as this can make it harder to fall asleep. If possible, try to exercise outdoors during the day to receive additional sunlight and further improve circadian rhythm.
Putting it all together
Combining the above habits, a circadian day might look like this:
- At 7 a.m, you wake up, go outside for a brisk 30 minute walk, and then eat breakfast at 8 a.m.
- You head to work, and eat lunch at 1 p.m.
- You arrive home and eat dinner, your last meal of the day, at 7.pm.
- From 9 p.m. until 11 p.m., avoid snacking or checking your phone or laptop, before sleeping at 12 a.m.
The above schedule is only a suggestion, and you may need to adjust it to fit your personal schedule.
Circadian rhythm can be thought of as an energy schedule, with peaks and dips during the day.
When your circadian rhythm is out of sync, you may feel tired during the day or struggle to sleep at night. On the other hand, maintaining a healthy circadian rhythm can leave you feeling energetic and focused during the day, and sleepy at night. By following a few simple daily habits, you can take steps to improve your circadian rhythm.
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