Sleep quantity & quality
A general rule of thumb is that as adults (18 to 65) we need between 7 and 9 hours of sleep a night in order to wake feeling refreshed, to function well during the day and reap the many benefits of sleep.
Most researchers concur and have concluded that for most of us seven to eight hours is the sweet spot. A large study of 1.3 million people revealed that the risk of death increases by 12 per cent for those who slept for less than six hours a night and by as much as 30 percent for those who slept for more than nine hours.
Firstbeat, the Finnish provider of the Lifestyle Assessment, has nuanced this by also considering the amount of the sleep time during which our body is in a restorative (parasympathetic) state. Their benchmark is to have at least 7 hours of sleep with our body being in a restorative state for at least 75% of the time asleep.
There are however large variations in our individual needs for sleep, which is influenced by age, life stages, genetics, health conditions, lifestyle patterns and other factors. Whereas most people need between 7 and 9 hours, approximately 8% of people can genuinely get away with 5 hours of sleep whereas 2% of people need more than 10 hours.
According to various studies the average sleep we get has dropped over the years. For example the American National Sleep Foundation in a 2011 study found the average of 8 to 9 hours has now dropped to about 7 hours per night. And the proportion of young adults (19-29 years) getting less than 7 hours sleep per night has more than doubled from 15.6% in 1960 to 24% in 2011.
Phenomenon such as sleep deprivation and sleep debt are real, and we can simply not condition ourselves to survive on less sleep. For example sleeping less than 5 hours a night for an extended period significantly raises the risk of health problems and even chronic sleep deprivation of, as little as, an hour a day can lead to a situation of sleep debt which causes (among other things) day-time fatigue.
A reliable indicator of whether you are getting enough and good quality sleep is day-time fatigue and sleepiness. The "Epworth Sleepiness Scale" can be a useful self-assessment to determine whether you may need to up your amount of sleep and / or address the quality of your sleep.
As alluded to, both quantity and quality matter. For good quality sleep we need to make sure we have the right combination of REM and non-REM sleep (refer to the Sleep Stages article for an explanation of the different sleep stages). Deep non-REM sleep facilitates recovery for our body and brain and this deep sleep dominates during the first half of our time asleep. REM sleep dominates during the latter part of the night and this is prioritised even if we haven’t had enough deep sleep.
Dysregulation of the Three Sleep Processes often affects in particular the first half of our sleep (refer sleep results from an example Firstbeat Lifestyle Assessment below). Consuming substances that contain caffeine, alcohol or other stimulates at night, exposure to blue light from screens, chronic stress and not allowing yourself to downregulate during the evening all immediately impact the quality of your sleep.
The deep sleep has been unable to do its job
As result only 52% of the sleep was restoratative
Explore The practice for restoring or enhancing sleep article to find out how you can positive influence the quantity and quality of your sleep.
