How much sleep is needed?
Sleep needs vary from person to person. The average amount of sleep for an adult is about seven to eight hours, but sleep needs range from five to 10 hours per night. Most of the restorative effects of a night’s sleep come during the first three to five hours when most deep sleep occurs. Some researchers have called this core sleep. Research shows it is easy to function normally during the day if you obtain this type of sleep. Research also shows that people with insomnia typically obtain their core sleep every night, despite believing they have obtained much less sleep.
Awakenings
Adults will usually wake up a few times during the night. This often occurs during the light sleep stages spaced across the night. Each awakening can be as short as a minute and often goes unremembered. When a person with insomnia wakes up in one of these normal awakenings, their fear and anxiety of being unable to return to sleep prolongs the waking period and causes further insomnia.
Perception of sleep
Sometimes when woken from light sleep, people can feel they were already awake. This is because the thought processes present during light sleep are similar to those we have if awake and relaxed in bed with our eyes closed. A common experience is to wake late in the night form light sleep and after a few minutes drift back to sleep, then wake up again 30 to 60 minutes later, but be completely unaware of the occurrence of the sleep in between.
The effects of aging on sleep
People usually begin sleeping less as they enter middle age. The number of awakenings through the night increases as sleep becomes lighter and people rarely enter the deeper stages of sleep. Lighter sleep with more awakenings is normal in older adults and has no damaging effects on daytime functioning.
Consequences of losing sleep
Most people assume that loss of sleep causes their mental and physical abilities to decline. Research on sleep deprivation shows that the body has a remarkable tolerance for sleep loss.
Making up lost sleep
Sleep following sleep deprivation is deeper and more efficient than usual. This means that it is not necessary to make up lost sleep on an hour-for-hour basis. It does not take a long time to recover from one or many nights of poor sleep.