The commonly accepted standard of eight hours as the ideal amount of sleep is a pretty good rule of thumb for most adults, but the National Sleep Foundation and most other sources recommend those ages 18-64 get seven to nine hours nightly (it varies only slightly for older adults, at seven to eight hours).
It’s rare to be able to function at your best on any less than that — the gene that allows some people to get by with six hours is found in approximately 3% of the population. But you may want to know exactly where you fall on that spectrum for planning purposes or just to understand yourself a little better.
How do I know?
A typical sleep cycle consists of four stages, starting with three stages of non-rapid eye movement (NREM) and concluding with rapid eye movement (NREM), the deepest phase during which we dream.
For restful sleep we must experience all four stages of the sleep cycle, which takes around 90 minutes, and we generally need four to five cycles per night to complete the many tasks our bodies need to accomplish during sleep.
Dr. Michael Breus of www.thesleepdoctor.com recommends doing this to pinpoint how many hours of sleep you need:
Set your alarm for when you need to wake, and schedule your bedtime seven and a half hours ahead of that time. Try to practice good sleep hygiene in the evening by avoiding heavy meals, caffeine, electronics use 30 minutes before bedtime and other things that may disrupt your sleep.
Take note of whether you wake up before or after the alarm goes off. If it happens around five to 10 minutes before or after you’ve been doing this for about a week that’s a good indication you got the sleep you needed. If the alarm jolts you awake, and especially if you’re still groggy, then try going to bed about 30 minutes earlier the following week.
Keep adjusting your bedtime until you settle on the right amount of slumber for you to wake refreshed and maintain your energy throughout the day. Stick to that bedtime once you find it!