It is recommended for adults to have 7-9 hours of sleep every day. If you think that’s a lot of time and that you could have done something productive at that time, then it depends on what you mean by productive because resting the body for 7-9 hours is fruitful itself.
The body goes through a lot while you sleep so you can be more productive when you wake up. It goes through stages of sleep. Along with knowing that you need 7-9 hours of sleep a day, it is also important to know how much you need per stage of it.
There are five stages of sleep that rotate between non-rapid eye movement (NREM) and rapid eye movement (REM) and include drowsiness, light sleep, moderate to deep sleep, deepest sleep, and dreaming.
Experts have recommended that adults gets about 7 to 9 hours of sleep per night. New research aims to identify not just how much total sleep you need — but also how much of each stage of sleep you need.
Sleep stages 1, 2, and REM consist of light sleep, while 3 and 4 comprise deep sleep.
Healthy individuals need about a quarter of the total number of sleeping hours to be in deep sleep.
In healthy adults, about 13 to 23 percent of your sleep is deep sleep. So if you sleep for 8 hours a night, that’s roughly 62 to 110 minutes.
However, as you get older you require less deep sleep.
During deep sleep, a variety of functions take place in the mind and body:
- memories are consolidated
- learning and emotions process
- physical recovery occurs
- blood sugar levels and metabolism balance out
- the immune system is energized
- the brain detoxifies
The same goes for REM sleep. The REM cycle starts at 1 ½ hours after you’ve fallen asleep and repeats at the same time interval.
For most adults, REM takes up about 20 to 25 percent of sleep, and this seems to be healthy during average sleep cycles. However, sleep research is raising some interesting questions. One recent study suggested that higher amounts of REM sleep may be associated with depression. But don’t go making sudden changes in your sleep habits — it is not clear which is the cause and which is the effect.
For light sleep, the stage when you are in transition to a more stable sleep, there is no minimum. But you have to remember that too much of it has consequences.
Although sleep scientists believe that light sleep is good for you, there is no minimum to strive for. Light sleep is usually the default stage, one that is nearly impossible to avoid if you are asleep at all.
Too much overall sleep on a regular basis, however, is linked to obesity, depression, pain, heart disease, and even increased risk of death.
Babies and kids need more sleep than adults do.
Babies and children need more sleep than adults. Babies need the most, spending about 16 of every 24 hours asleep. Approximately 50 percent of their slumber is spent in the REM stage, while the other 50 percent is divided between stages 1 through 4 and NREM sleep that cycles between light and deep.
As children grow older, the amount of sleep they need varies:
- toddlers: 11 to 14 hours
- preschoolers: 10 to 13 hours
- school-aged children: 9 to 12 hours
- teens: 8 to 10 hours
Sleep should make you feel rejuvenated the next day. If you don’t feel like you are and instead feel tired, you might not be getting the recommended number of hours of sleep per day as well as its sub-stages.
According to the American Sleep Apnea Association, you should feel fresh and alert when you wake up, but many people don’t.
If you’re sleeping for 7 to 9 hours each night, but only 10 percent of that is deep sleep, you’re not getting the 90 minutes you need and might still be tired each day. A sleep study may help you figure out what is going on.
There are a number of possible causes that you might want to discuss with a doctor, including:
- general sleep disorder
- obstructive sleep apnea
- not getting enough sleep
- getting too much sleep
- other health conditions that cause fatigue