Sleep can be more or less efficient. If you sleep for a long time there is a risk that the sleep will be inefficient, & you just waste your time(although it is of course pleasant & dreams can often be inspiring). There is also some evidence that imply that people who sleep longer more often develop depressions, that can be ameliorated or cured by reducing the length of sleep & the introduction of more light during waking hours. In general it is good to be surrounded by light during waking hours(preferably bright sunlight), & darkness when one plans to sleep to adjust the biological clocks correctly(the superchiasmatic nucleus in hypothalamus, which regulates our rhythms, is linked to the optic nerve & reacts to light/darkness).
It is currently a bit unclear how much sleep is needed per night, but four hours seems to be the absolute minimum for normal function. Normal sleeping time is 6 hours for adults, while the body will(if allowed) shift to a 8.5 hour sleep every night. There are no doubt individual differences, & the length of sleep is also dependent on our habits.
The lightbulb has changed our sleeping habits to a large extent; earlier the sunset marked the beginning of the night & sunrise the beginning of the day, but today most people(at least in the cities) remain awake a long way into the night. According to the old biological rhythms we should awaken at 8 in the morning, not at 6 as most people do. At this early time the melatonin concentration is at its greatest, & it makes us tired and sleepy.
It is worth noting that there exists two kinds of sleep, mental sleep & physical sleep. The body needs rest to replenish energy resources & some forms of repair, while the brain appears to do’garbage collection’ during sleep. These two forms of sleep do not have to coincide, although they usually do. It should be possible to relax & rest the body while remaining mentally active, for example in some forms of meditation or just lying in bed reading(in the latter case some ergonomic design is needed to avoid tensing too many muscles).
Beside the major 24-hour rhythm there are other short-periodic rhythms in our activity levels. Most people experience a dip in activity after midday, corresponding to the siesta in warmer countries(a quite natural adaption to the noon heat). A related periodic activity change seems to have a period of six hours; after waking up at six the mind & body feel tired to around nine, when they start to become efficient & clearly awake. This active state lasts for around three hours until replaced by the early afternoon dip, which can last to until three, when another activity period begins. These times are of course different for different persons, but by acting on your biological rhythms you can plan your day for maximum efficiency.
A System For Optimal Sleeping
. Go to bed at 3.30 in the morning.
. Wake up at 8.00
. Take two half-hour naps, one in the afternoon and one in the evening.
This will give you approximatively 5 1/2 hours of sleep per day, distributed more evenly than the usual sleeping pattern. The timing should of course to be adjusted for your own daily rhythm. To make your sleep efficient is a matter of training, & it is not possible to achieve it through pure willpower(which will just undermine your efforts, since having to go to sleep is one of the best ways of avoiding it).
General Advice
Sleeping habits should remain unchanged from day to day, otherwise it will become hard to fall asleep or wake up at the correct time. If you go to bed & rise the same time all days(including in the weekends, when many people sleep extra long) your biological clock will adjust to it, making it easier to pass from one state to another on cue.
The last cup of coffee, cola or tea should be drunk in the early afternoon.
Take a walk each day in daylight to strengthen your biological rhythm.
When going to bed, stop worrying & planning. After all, you cannot solve the problems at hand(consciously) while sleeping, & afterwards you will be rested & much more able to handle them effectively.
Sleep in a dark, cool & calm place. When you awake, let in as much light as possible(I use to stand at a window soaking in the sunlight, weather permitting). Before going to bed it is a good idea to gradually lower the light-levels around you(note that only lightbulbs are needed for influencing the biological clock, strong fluoroscent light or sunlight are useful but not necessary).
Sport & exercise are best done in the afternoon, not in the evening(since this causes the metabolic rate to increase so that you will not be able to sleep).
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Sleep WELL!