Reducing the amount of time you spend asleep may increase your risk of developing conditions including obesity, depression, and hypertension. But some habits may help you feel more awake.

Getting a full night’s sleep not only feels good, but it also improves your mental performance and boosts your overall health. Most adults need more than 7 hours per night for optimal well-being. Children and teenagers need even more to support their development.

Teens should sleep 8 to 10 hours per night, grade-schoolers 9 to 12 hours, and preschoolers 10 to 13 hours.

Many people wonder if it’s possible to “hack” their sleep so that they spend fewer hours in bed but still wake up feeling rested and productive. The short answer is yes and no — but mostly no.

The quality of your sleep plays a role in determining how rested you’ll feel when you wake. Improving your sleep quality can reduce the number of hours you need to spend in bed.

However, even if your sleep quality is great, sleeping for fewer hours than what’s recommended is detrimental to your health and mental performance. You may be able to do it for a few days, but eventually, the lack of rest will catch up with you.

Keep reading to find out why it isn’t possible to feel rested after getting only 4 hours of sleep per night over a long period. We’ll also look at why some people seem to be able function off much less sleep than others.

For most people, 4 hours of sleep per night isn’t enough to wake up feeling rested and mentally alert, no matter how well they sleep.

There’s a common myth that you can adapt to chronically restricted sleep, but there’s no evidence that the body functionally adapts to sleep deprivation.

Also, people who exercise regularly often need more than the minimum recommended hours to give their bodies time to regenerate from the additional physical stress.

A 2018 study that examined the sleep habits of more than 10,000 people found that regularly getting 4 hours of sleep per night was the equivalent of adding 8 years of aging to the participants’ brains.

Getting fewer than 7 hours of sleep per night over a long period may increase your risk for developing complications like:

Sleep requirement genetic mutation

There’s one caveat when it comes to how much sleep you need: Everybody’s body is different, and some people can thrive off fewer hours of sleep than others.

Scientists have found a rare mutation of the ADRB1 gene in people who are able to feel rested with less than 6.5 hours of sleep per night without any apparent health consequences.

If you carry this gene mutation, it’s possible that you may feel rested even if you consistently sleep less than the recommended number of hours.

Polyphasic sleep

Polyphasic sleep refers to sleeping multiple times in a 24-hour period instead of once per night.

There are many different polyphasic techniques. One of the most common programs involves taking six 20-minute naps spaced equally throughout the day for a total of 3 hours a day.

Many people claim that polyphasic sleep allows you to sleep more efficiently and achieve the same amount of rest in fewer hours. However, there’s no medical evidence that polyphasic sleep is better than traditional sleep.

Sleep deprivation on polyphasic programs likely has the same negative health consequences as other forms of sleep deprivation. However, there’s limited research on these types of programs, since the vast majority of people who follow polyphasic programs only stick with them for a short time.

Chronically cutting your sleep short isn’t a good idea, but life gets busy and sometimes sleeping adequately isn’t possible for a few nights. The more nights you limit your sleep, the more “sleep debt” you’ll rack up. As with financial debt, the more sleep debt you have, the harder it is to pay it off.

There’s no magic way to increase your energy while cutting your sleep. However, the following techniques may help you get through short-term periods of sleep deprivation.

  • Get some light exercise. Exercising lightly can stimulate blood flow to your brain and temporarily make you feel more awake. However, heavy exercise may make you feel even more tired.
  • Avoid screen time for an hour before bed. Screens emit blue light, which may interfere with your body’s natural circadian rhythm and melatonin production.
  • Keep screens and other distractions out of your bedroom. Removing your phone and other potential distractions from your room can help limit idle time in bed that will cut into your sleep.
  • Make sure your room is dark. Bright lights in your bedroom may interfere with your body’s natural production of melatonin.
  • Reduce caffeine intake. Caffeine is a stimulant that acts on your central nervous system and can reduce drowsiness.
  • Eat a healthy diet. Eating an overall healthy diet can potentially give you more energy throughout the day.
  • Avoid alcohol. Alcohol has a sedative effect that reduces activity of your central nervous system and can make you drowsy.
  • Avoid liquids before bed. Avoiding liquids reduces your chances of needing to get up to use the bathroom in the middle of the night.
  • Try napping. Taking short 20-minute naps throughout the day may help give you recharge without causing you to feel drowsy.
  • Spend time in daylight. Exposing yourself to sunlight may improve your focus by stimulating the production of serotonin.

If you’re experiencing the following side effects, it’s likely a sign that you need to sleep more. It’s a good idea to prioritize rest for the next few nights until you notice your mental function return to normal.

Your body cycles through four stages of sleep throughout the night. One cycle takes about 90 minutes.

During a typical night’s sleep, you’ll cycle through each stage four to six times. If you’re limiting yourself to 4 hours of sleep, you’ll only have time to cycle through these stages twice.

The sleep stages are:

  • N1. This is the lightest stage of sleep, lasting 1 to 5 minutes. During this stage, your breathing and heart rate slow down and your muscles relax.
  • N2. This stage lasts about 30 to 60 minutes. Your breathing and heart rate slow down even further and your body temperature drops.
  • N3. The third stage of sleep is also known as deep sleep. This period, which lasts about 20 to 40 minutes, is when your body repairs damaged tissues and cells.
  • Rapid eye movement (REM). REM is the stage most associated with dreaming. Your first REM cycle lasts about 10 minutes and your last one can last up to 1 hour.

Most adults need at least 7 hours of sleep per night to wake up feeling rested and mentally fresh. Limiting your sleep raises your risk for developing many health problems such as diabetes, depression, or cardiovascular disease.

If you have to limit your sleep for a few days, you can potentially increase your energy by spending time in the sunlight, taking short naps throughout the day, and performing light exercise.

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