We start the night in light sleep and have all our deep sleep towards morning therefore if we shorten our sleep time we will miss the best part of our sleep.
We cycle through all stages of sleep every 90 minutes (range 70 to 100 minutes). Most of our deep sleep occurs in the first 2 sleep cycles – not towards morning. Interestingly, if sleep is curtailed, deep sleep is usually maintained at the expense of light sleep and dream sleep.
Good sleepers do not wake during the night.
Waking is a normal part of sleeping. Even young healthy sleepers will wake 2-3 times every night but they usually do not remember waking. We are more likely to remember a wake period if it occurs after a dream. Wake periods are only problems when we start to think or worry after we wake which can make us more alert and prevent a return to sleep.
Dream sleep is deep sleep.
Dream sleep is not deep sleep but is very similar to an awake state where the brain is busy processing information. During dream sleep our body is semi-paralysed so we do not get up and act out our dreams. Dream sleep is also important in the processing, transfer and storage of information.
As we age we need less sleep.
With increasing age there is more fragmentation of sleep and sleep quality is reduced. If an older person is healthy then these changes are usually manageable. However with increasing age many individuals also have other health conditions which negatively impact on sleep independently of age alone.
An hour of sleep before midnight is worth 2 hours of sleep after midnight.
It is unclear where this myth came from but it may have come from parents wishing to get their children and teenagers to bed by a suitable time! Regardless of the time of sleep onset most deep sleep will occur in the first 1-3 cycles of sleep. More recent research shows that teenagers who experience delay in their sleep onset times (often from using electronic devices) are more likely to be sleep deprived, experience greater performance impairments and have more difficulties with mood.