Is 4 Hours Of Sleep Enough? Here’s The Scientific Truth

Have you ever tried to get by on just a few hours of sleep? How did it go? If you are like me and the general public, it probably didn’t go so well.

So, how do people who say they sleep only four hours a day do it? Is four hours of sleep even enough? Here’s the scientific truth.

get enough sleep

Is It Possible?

Some people have said that they can get by on just 4 hours of sleep. Sometimes they make you feel lazy for sleeping longer, even if you only get about 6 hours at night.

This begs the question – ‘Is it possible to survive on only 4 hours of sleep daily?’ According to Dr. Fu, it is.

Dr. Ying-Hui Fu, a seasoned neuroscientist who currently serves as a neurology professor at the University of California San Francisco, has done numerous studies in the field of sleep. She has proven, through genetic testing, that there is a set of people who are naturally short-sleepers.


The thing about these people is that they are naturally wired to sleep for short periods of time. They have a genetic mutation that keeps them from sleeping for long. No matter what time they go to bed, they are wide awake and fully refreshed after only a few hours of sleep.

This set of people are likely to survive and thrive on 4 hours of sleep per day. But this is ONLY because their bodies are designed that way from birth.

short sleep

There’s another category of short-sleepers. These are the ones likely to make you feel bad for sleeping a normal length of time. These are the trained short-sleepers.

They train their bodies to ‘need’ less and less sleep by waking up progressively earlier or going to bed later and later until they get to the desired number of hours of sleep.

The upside is that they get more hours of waking time to do anything – work, play, or eat. The downside, which is a major deal breaker, is that they reap all the ‘badness’ of poor sleep. A commonly experienced downside is frequent illnesses like the common cold.

frequent illness

If you have considered training your body to require less sleep, I assure you that the downside definitely outweighs the benefits. Let’s prove this by showing you what happens when you don’t get enough sleep.

Is 4 Hours Of Sleep Enough?

The question we asked at the beginning of this article ‘Is 4hours of sleep enough?’ can be answered in one word – No! Unless of course, you are one of the few genetically programmed people that require only a few hours of sleep.

We highly recommend that you stick to the N.S.F. standard of sleep (which is about 7-9 hours daily) and practice good sleep hygiene.

Effects Of Decreased Sleep

Sleep is a very important aspect of daily living. The National Sleep Foundation (N.S.F.) recommends that an adult should get about 7 to 9 hours of sleep daily. Forcibly reducing this required quantity by training may result in certain unwanted effects. Some of these effects include –

1. Lowered Immunity

Sleep is a time where the body rejuvenates and strengthens itself, including the cells responsible for fighting off disease-causing germs. When we deprive ourselves of sleep, our immune system is weakened, allowing these bugs to take over. People who don’t get enough sleep frequently develop colds and other infections.


2. High-Stress Levels

When we sleep, we de-stress. This happens on a mental and hormonal level. On the mental level, the brain rests and prepares itself for a new day. On the hormonal level, stress hormones decrease when we sleep.

If we don’t get enough sleep, the brain can’t reset properly meaning we won’t be able to handle any more stress from our day. Also, when stress hormones are consistently high, it leads to skin changes and imbalanced blood sugar levels.

high stress

3. Impaired Judgment

Poor sleep has been linked to a lot of accidents. When we don’t get enough sleep, our judgment is impaired and we make decisions we wouldn’t normally take if we were well rested.

4. Poor Concentration

As mentioned earlier, the brain resets when we sleep. If this doesn’t happen due to poor sleep, the brain can’t take on more work because it hasn’t finished processing the work of the previous day. Basically, without sleep, the brain can’t function at full capacity.

5. Decreased Cognitive function

The cognitive function of the brain includes its ability to think and learn. When the brain isn’t rested due to a lack of sleep, there is a decline in its cognitive functioning. This simply means that we would find it difficult to think and learn if we are sleep deprived.

difficulty thinking

6. Irritability

You may have experienced that cranky feeling you get when you haven’t gotten enough sleep. Without sleep, we become unbearable and easily irritated with things that we would normally overlook.

7. Poor Memory

During sleep, one of the many things the brain does is to store memories and recently learned activities. Without good sleep, some of these memories are lost in transition. This is because memory consolidation occurs in the later part of the night after about 4- 5 hours of sleep during REM sleep. The shorter the length of your sleep, the less REM sleep you get and the less memory retention you achieve.

8. Hypertension

Studies have shown that people who sleep less, for example, insomniacs, have an increased risk of developing hypertension. This is, in part, due to the consistently high levels of stress hormones in the circulation.

You may be at an even greater risk if you consistently sleep short hours and you have family members with hypertension.

9. Diabetes

The Diabetes epidemic is also thought to be greatly influenced by people sleeping fewer hours daily. Once again, the stress hormones are partly to blame. The stress hormones cause an increase in the blood sugar levels and over time, this may lead to diabetes.

check blood sugar

10. Higher Risk Of Cardiac Disease

Multiple studies carried out have linked a lack of sleep to an increase in the occurrence of cardiac diseases such as heart attack and irregular heart rhythm.

11. Loss Of Libido

With poor sleep, the body tries to conserve its energy for important things like cellular functioning and repairs. Sexual relations are not a priority for it at this point causing the body’s drive for intercourse to be reduced.

12. Depression

Depression and poor sleep go hand-in-hand. One of the commonest signs of depression is a lack of sleep and a lack of sleep causes one to have a depressed mood. Some studies have shown that people with insomnia have a much higher risk of becoming clinically depressed.

13. Premature Aging

It is during sleep, deep sleep in particular, that the body repairs itself. It rejuvenates the worn out cells, especially that of the skin. When we lose sleep, our skin loses its glow, elasticity, and smoothness. We get wrinkles and dark circles under our eyes.

The cause of this can be traced to the stress hormones – again! These hormones cause the breakdown of collagen, a very important protein that gives our skin its elasticity and smooth texture.

14. Increased Weight

Two hormones maintain the balance we have between hunger and satiety. When we sleep, the satiety hormone (leptin) increases and the hunger hormone (ghrelin) decreases. When we don’t sleep, the reverse happens, causing us to be hungry all the time.


This phenomenon is one explanation as to why our generation is getting heavier and having more obesity-related illnesses. Studies have shown that people who slept the recommended length of time were less likely to become obese when compared to those who slept less than 6 hours.

These are only some of the effects of poor sleep. Poor sleep is not only about sleeping too little; it also includes the quality of your sleep. However, having an adequate amount of sleep is the beginning of good, quality sleep.

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Oyinkansola Kolawole, MD

Dr. Oyinkan Ogundimu is a graduate of medicine and surgery. She migrated to the United States to pursue her dream of caring for patients, her passion in life is to help people in all the ways she can including breaking down difficult to understand medical facts into simple and fun bits of information.
Oyinkansola Kolawole, MD