What’s the minimum amount of sleep I need to function well?
The base amount of sleep you need is personal to you and will depend on a variety of factors, including your age, health, activity, and stress levels.
As a general guide, adults require between seven and nine hours’ sleep a night for the brain and body to perform all the necessary biological tasks that can only happen during sleep. Just a few nights of four hours’ sleep has been shown to negatively affect heart rate, blood pressure, mood, and memory—although effects are reversed when you start sleeping normally again. Although many people report that they function well on five or six hours’ sleep a night, that fact is that most will be chronically sleep-deprived.
AM I A TRUE SHORT SLEEPER?
A few people—thought to be less than 1 percent globally—are naturally able to thrive on less sleep due to a quirk in their genetic code. A gene mutation, named DEC2, appears to work by making it easier for the body to produce more orexin, which wakes us up and keeps us alert. Studies show that people with this mutation are able to sleep for around six hours with no impact on their daytime performance. Research also found that the family members of short sleepers had another rare genetic mutation called ADRB1, which affects their sleep/wake cycle.
Although there is no widely available test to confirm if you are genetically a short sleeper, if you tend to be highly active and efficient, feel well rested in the morning, and have relatives with similar traits, it could be that you are a member of this exclusive club.
Science of staying awake
Since the discovery of the first “short-sleep gene” in 2009, researchers have identified two further mutations that may also enable natural short sleep.
CAN I SLEEP TOO MUCH?
Around 2 percent of people are affected by “hypersomnia”—they may need as much as 10–12 hours’ sleep every night and still feel sleepy and nap in the daytime. This excessive sleeping has many different causes, some of which are genetic; it can also be a side effect of prescription medication or a symptom of depression. Specific sleep disorders that shorten or disrupt nighttime sleep may also prompt sufferers to spend extra daytime hours in bed to compensate.
While research findings vary, there is some evidence that habitual oversleeping may be as detrimental to health as too little sleep. Studies have found that both can be associated with a higher risk of developing certain conditions (see below).
Too little sleep:
- Reduced reasoning skills
- Higher risk of obesity due to hunger and overeating
- Higher risk of heart disease and strokes
- Possible risk factor for dementia
less than 6
hours’ sleep
Ideal amount of sleep
- Many scientific studies have identified seven to nine hours’ sleep as the optimum length of sleep to maintain physical and mental health in the vast majority of adults
7–9
hours’ sleep
Too much sleep:
- Reduced reasoning ability
- Links to faster cognitive decline
- Higher risk of heart disease and strokes
- Possible early warning sign of dementia
more than 9
hours’ sleep