Sleep is most restorative when it occurs in sync with the light-dark rhythms of the planet. Ideally, melatonin production is suppressed during the daytime due to bright light exposure, and in the evening, melatonin production increases due to the absence of light. Therefore, it is obvious that the ideal time to sleep is from nightfall to dawn.
In order to maximise the benefits of sleep, keeping to a regular sleep schedule can be useful. In other words, short-changing yourself on sleep during the week and sleeping in on the weekend isn’t ideal. Of course, that is better than short-changing yourself on sleep during the weekend too, but it would be much better to get adequate sleep every night. And for most people, that means prioritising sleep. Instead of staying up until 11pm or midnight doing extra work or watching television, it is better to stick to a regular schedule that will allow you to get adequate sleep every night at roughly the same time.
Respect your body rhythms
Remember that our bodies synchronise their rhythms based on cues from the environment. If you sleep in on Saturdays for an extra two hours, your body tries to synchronise to the new set of cues [later light exposure]. But then on Monday when you try to get up at 6am, you’ll struggle. So if you usually get up at 6am, it is generally better to always get up at that time [except if sick or really in need of the extra sleep, of course]. Therefore, if you require a full eight hours of sleep each night, that means you need to be asleep by 10pm each night. Or if you need nine hours, then you need to be asleep by 9pm each night.
The waking period was historically viewed as a time of increased creativity
Now, of course, all that is assuming that you are a monophasic sleeper, meaning that you strive to sleep in one, continuous block of time. That is the conventional way in which most of us now sleep. However, there is evidence that this has not always been so and that it may not be the ideal way to sleep.
Try biphasic sleep
A number of historians, including, most prominently, Roger Ekirch of Virginia Tech, argue that until the industrial revolution, segmented or biphasic sleep was the normal type of sleep for humans. Specifically, they suggest that normal sleep patterns for humans involve two periods of sleep interrupted by a period of wakefulness in each night. Each sleep period is estimated to be approximately four hours, and the waking period is between one and three hours.
The waking period was historically viewed as a time of increased creativity. Researchers have confirmed that when modern humans are placed into conditions with 14 hours of darkness, they naturally and spontaneously settle into this very pattern of sleep. In most temperate locations, there is a considerable difference in the length of night between summer and winter. It is unlikely that biphasic sleep would occur as regularly during the peak of summer, but in the rest of the year [spring, fall, and winter] biphasic sleep would likely be normal.
Does that mean you should strive for biphasic sleep? Not necessarily. But if you have struggled with sleep or if you find that you naturally wake after about four hours of sleep and find it difficult to get back to sleep, you may want to experiment with this pattern.
If you do shift work, then it seems likely that the very best thing you can do for your health is to work during the day instead
If you work in shifts…
Lastly, when speaking of when to sleep, no discussion would be complete without a mention of shift work. Shift work [meaning work schedules that go into the night or early morning] is a known risk factor for many conditions, including cardiovascular disease, diabetes, cancer, headaches, fatigue, and weight gain. In addition, not surprisingly, shift work is notorious for causing sleep disorders. In fact, one such disorder is named ‘shift work sleep disorder’.
If you do shift work, then it seems likely that the very best thing you can do for your health is to work during the day instead. However, if that is not possible or viable for you, there are a few things you can do to help improve your sleep and your health.
First, since you cannot control the natural lighting during your waking or sleeping hours, you can at least take some steps to try to improve your light exposure. However, at the end of your shift, reduce the amount of light exposure. When you get home, make an effort to greatly reduce your light exposure, particularly to blue light. Your sleeping environment, ideally, would be made completely dark, which can be achieved by placing an opaque substance over the windows such as aluminium foil. Then, follow all the other suggestions for ways to minimise your light exposure, including removing lights from electronic devices from the bedroom.
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