These observational studies suggest generalized ranges for healthy sleep duration, but on an individual level, each of us is different – and every one of us has different sleep requirements.
Some people are genetically predisposed to need less sleep than others. A very small percentage, called short sleepers, function normally with 5 or less hours of sleep. Determining the right amount of sleep is also a moving target – it changes as you age.
National Institutes of Health
Normal changes in total sleep and percentage of REM sleep over time
A century ago, before widespread artificial lighting, we tended to stay longer in bed during winter when the days are short and nights are long, sometimes spending 10, 11, 12 or more hours in bed. There are widespread historical records showing normal sleep a century or more ago during winter was more biphasic, with two blocks of sleep separated by two or more hours of wakefulness in the middle of the night. Today this is sometimes called the “first sleep, second sleep” phenomenon.
Back then, people might sleep for four solid hours, wake up for two or more hours, then fall back asleep again until morning. The wakeful period in the middle of the night was called “the watch” or watchful sleep period. This was generally described as a period of quietness and peacefulness, almost like a meditative state.
So if in the night, and especially during long winter nights, you sometimes find yourself awake between cycles of sleep, remember you are only a few generations removed from when this was more of the norm.
In addition, as we age, the quality of deep sleep – the most restorative sleep characterized by deep brain waves – tends to be reduced, and sleep tends to become more fragmented. Most experts agree as we age we still need just as much sleep as when we were younger, but we are more likely to be disturbed by outside environmental factors, like a snoring partner or barking dog.
Psychiatry Reference - PsychDB
Sleep is a moving target: it changes as you age.
This means our inherent sleep system tends to naturally become a bit more fragile as we age. Sleep scientists are not sure exactly why this happens – one theory is that sleep is like many other physical abilities that normally tends to diminish in strength as we age. Despite this diminishment, however, many of the healthy elderly self-report satisfaction with their sleep as they age, in some cases significantly more than people half their age.
Using the proven methods in the STS to strengthen your sleep system, there is every reason to believe that you too, like many others, can restore and maintain the quantity and quality of your sleep to your satisfaction as you age. And if you find you awaken more easily as you’ve gotten older, be assured this by itself is not some sort of inherent defect; rather it is considered normal and nothing to worry about.
Determining the right amount of sleep for you is a personal decision
There are many interrelated factors that determine how much sleep is best for you, including your unique metabolism, which changes as you age. Your sleep can be affected by your diet, your occupation, the amount of stress you experience on any particular day. Your sleep can be influenced by the amount of exercise you get, and many psychological factors we will soon consider in depth.
The bottom line? There is no one specific number of hours that is the “right” amount everyone should get. Instead, there is only one number we are concerned about: what’s right for you, and the STS will help you determine that.
As a starting point, if you believe that somewhere between 7 to 9 hours a night is right, you will most likely be on the right track. Using the STS’ interactive Sleep Logs as a tool, you will be able to progressively adjust the amount of time you allow for sleep to best fit your own unique situation.
Now, with a factual and scientific basis for understanding the dynamics of sleep, we have a solid foundation for working with the STS.