The physiological processes behind sleep are fascinatingly complex. And if you should know anything about them to improve your sleep, it is this: your body has a clock! And you can work with it or against it.
Our body clock tells us to go to bed in the evening and wakes us up in the morning. When working properly, it tells us to go to bed and to wake up at approximately the same time every day. What is even more interesting, it tells us to go to bed and wake up at the same time regardless how much we’ve slept. So the beauty of this is that if you collaborate with your body clock, you will not need an alarm in the morning, but will wake up naturally, well-rested, every day. How does this work?
Body clock and melatonin
To simplify things, this works because our body secretes hormones that regulate sleepiness. You have probably heard of melatonin – melatonin is one such hormone. When levels of melatonin are high, we feel sleepy. When levels of melatonin are low, we feel more awake. Levels of melatonin fluctuate naturally and have an approximately 24-hour cycle. If everything is working as it should, the high levels of melatonin will coincide with the astronomical night, when we need to be sleeping. By morning, the biologically driven urge to sleep will decrease and we will feel awake.
Jet lag: body clock and long-distance travel
You can best observe that your body has a 24-hour “sleepiness cycle” when you travel across several time zones. Our body clock cannot be reset as quickly as the clock on our smartphone, so when you travel far, the body clock will be out of sync with the astronomical time for a few days. Let's say you fly from Paris to New York. On the first day, your body clock may tell you it’s time to sleep at 5 pm local New York time because in Paris, it is your regular 11 pm bedtime. But even if you resist the urge to sleep and stay awake for a few more hours, you may still wake up at 3 am and have hard time falling back asleep because in Paris, it is already 9 am, when you usually are wide awake. This is called jet lag: your body clock is out of sync with the local time.
Luckily for frequent travelers, over the course of a few days our body clock can re-synchronize with the astronomical time, so that we feel sleepy at appropriate hours. This is possible because our circadian rhythms readjust every day based on the signals the body gets from the environment, light and darkness being among the most important signals. When it gets dark, the body starts producing melatonin. When it is bright, the light blocks melatonin and we feel more alert. (And that, by the way, is also true for light emitted by TV, computer, and smartphone screens; this is one of the reasons why some people find it hard to fall asleep right after watching TV, browsing Internet, or reading from the phone). So in our Paris to New York example, you will eventually stop wanting to go to bed at
5 pm New York time because you will be exposed to light in the evening.
Andvanced and delayed sleep phase
We can also be out of sync with the local time even if we don't travel. For example, you go to bed much earlier than everyone and are up for the day at 4am. Or you go to bed at 2am and get up at 10am, unless you have to be somewhere in the morning. This is called advanced / delayed sleep phase syndrome respectively. Tendency for either of these extreme is biologically determined, but you can still adjust your body clock to be on a more socially acceptable schedule. Doing so would require you to delay your bedtime by 15 minutes every few days if you go to bed too early. If you go to bed too late, to correct that, you would need to more your normal wake up time to 15 minutes earlier every few days.
When the rhythms are regularly disrupted
To summarize, it is natural for our body to go to bed and wake up at approximately the same time every day. This is what it is designed to do. If we support these rhythms and try to keep a regular schedule making sure we give ourselves enough opportunity to sleep, we will be falling asleep easily at night and waking up naturally without an alarm every day (although a short period of adjustment may be needed when we might still use an alarm to establish the new rhythms).
Now let us consider what happens when we don’t have a steady schedule (which, let’s face it, most of us don’t). If you go to bed and wake up at different times every day, your body clock won’t have a chance to follow its natural 24-hour rhythm. And while this may seem like the norm for many – most people do get up earlier on week days and sleep in on weekends – it has unfortunate consequence for our health and performance.
First, if you need an alarm to wake up to go to work, you obviously wake up earlier than you are ready to. The result is that you feel tired and have less than optimal concentration during the day. You may be so used to feeling this way on your work days that you think it’s the default, but it’s not.
Second, it is not only sleepiness that follows a 24 hour pattern. During sleep, complex physiological processes take place that ensure mental and physical restitution. To name just a few examples, sleep is needed to regulate the metabolic function, boost the immune system, and restore cognitive performance. Those processes also follow the biological clock and have a 24-hour cycle. Having a different schedule every day may therefore compromise the body’s and the brain’s ability to fully recover and restore during sleep, and there will be a price to pay. Not surprisingly, we see that people who have irregular schedule, for example shift workers or people who have a big difference between work day and weekend schedule, are at higher risk for various health problems, including depression, overweight, obesity, and other metabolic issues.
... if you wanted to get full advantage of your sleep, you would:
Go to bed and get up at the same time every day (plus or minus 30 minutes).
Make sure you are getting enough sleep every day, so you don’t need to catch up on sleep on weekends.
Unless your work schedule and lifestyle allows you to go to bed and get up whenever, adjust your body clock to be in sync with your daily obligations.
Are you curious to discover what your body clock can do for you? Then see if you can collaborate with it for a month and judge for yourself!