We would all like to have it.
A healthy brain – and even most brains with sleep disorders – transitions abruptly between sleeping and waking. Some awakenings may feel more abrupt than others – a ringing alarm clock – but the amount of time spent truly in a period of neither waking or sleeping – either at morning or night – is small. For mammals only about 1% of the day is spent truly in transition and this is a function of the robustness of the sleep/wake dicotomy. So even though we at Sleepdex like to talk about parasomnias and microsleeps and microarousals and sleep inertia, it is worth remembering that most of the time an external observer can easily tell if a person is awake or asleep
Most adults sleep at night in a single unified period of 7 to 8 hours. There are both evolutionary and social reasons for this. Like our closest animal relatives, humans are diurnal. We find it easier to sleep when it is dark and cool. Because the large majority of people living near you are sleeping at night, it is more convenient to do at roughly the same time. lthough sleeplessness has occurred and been a bother for the history of man, the word insomnia in English was first recorded in 1623.
People can certainly sleep routinely at others times, as night workers and rotating shift worker do, but so often daytime sleep is more fragmented and shorter than nighttime sleep. We are made to sleep at night.
The circadian pressure is so strong it shows up when is at odds with the homeostatic cycle. For instance, many people, when forced to stay up all night, feel extremely sleepy by 3 to 4 AM, but start to feel less sleepy when the sun rises. Similarly, even when our sleep tank is filled up, so to speak, and we have slept relatively recently, when a regular bedtime approaches we may feel the desire to sleep.
It’s too bad that Mother Nature designed us to sleep 6 to 9 hours per night. It would be much more convenient if that time could be shortened, perhaps if we could sleep so deeply, soundly, and efficiently that our bodies and brains got all the recuperation they needed in 3 hours. The quest for a shorter sleep time has driven many sleep hacks and attempts to modify the cycle by adopting polyphasic sleep schedules.
Do you want to “sleep like a baby”? Yes, you probably do, in terms of sleep quality if not length. Babies sleep a lot, more than moderns adults with things to do probably prefer to sleep. But babies also sleep deep. Most of their sleep is spent in REM and slow-wave sleep; little in shallow Stage 1 and 2 sleep. Adults who find sleep unsatisfying typically spend too much time in light Stage 1 and 2 sleep.
Do you want to “sleep like a log”? Logs are inanimate objects and do not move. They might represent the unrestless sleeper. Movement during sleep is not necessarily bad and does not indicate troubled or unrefreshing sleep. Sleepers in REM do not move, but non-REM sleep can include movement. When people speak approvingly of sleeping like a log, they probably mean they had few or no nighttime awakenings, and a generally uneventful sleep period.