When we sleep, we go through three stages of sleep that make up a 90-minute cycle.
Each cycle creates various levels of brain electricity:
- Light sleep: Electrical activity is similar to the amount when you’re awake
- Deep sleep: Very low electrical activity relative to light and REM sleep
- REM sleep: (Rapid eye movement) sleep: A higher level of electrical activity than when you’re awake
Most people need between seven and nine hours of sleep for optimal brain health, but the number of hours is specific to you.
There’s a rare group of people who can function at high physical and mental levels on significantly less sleep. They’re called “short sleepers” and likely account for less than 1 percent of the population.1 Some people who think they’re short sleepers are actually sleep deprived—which makes them vulnerable to all the issues that come with lack of sleep.
If you’re sleeping more than nine hours a night, you should be evaluated by a physician. Excess sleep can be a sign of conditions such as heart disease, diabetes, and depression, and can raise the risk of memory issues, back and neck pain, and obesity.