Super-sleepers: Why can some people go on about their day on just 4 hours of sleep?

Sleep is essential for all human beings to function. However, not everyone needs the same amount of sleep to survive the chaos of this world.

Some people require seven to nine hours of shut-eye daily, while others can do just fine with only four to six hours of bedtime each night. These short sleepers are as well-rested as the rest of us who cannot do without our eight hours of daily sleep.

Now, scientists have discovered what works in favour of these people who thrive on only four hours of sleep – a rare genetic mutation.

Let’s take a closer look.

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How study was carried out

The research, published in the journal Proceedings of the National Academy of Sciences (PNAS), has found a mutation in people with a natural short sleep (NSS) trait that affects their sleep duration.

A 70-year-old natural short sleeper volunteered for the study. The healthy woman reported her regular sleep-wake patterns through an organised interview. Her sleep patterns were recorded via wrist actigraphy, according to Medical Xpress.

While the volunteer reported three hours of daily bedtime, the actigraph device signalled an average of 6.3 hours of sleep each night. The researchers collected her DNA samples and carried out whole-exome sequencing to identify genetic variants that could be making her a super sleeper.

They found a mutation – N783Y – in the salt-induced kinase 3 (SIK3) protein kinase.

What the study found

Previous studies have identified five mutations in four genes that are linked with short sleep in humans, as per a Medical Xpress report.

Now, researchers say that one of these mutations alters the protein structure of SIK3. The mutation – N783Y – that changes the structure of this gene plays a key role in determining sleep and wakefulness, as per an Independent report.

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The scientists studied this mutation – SIK3-N783Y – in genetically modified mice, which were found to sleep an average of 30 minutes less each night, compared to other mice.

After further analysis, they discovered that the mutation led to structural changes, impairing the protein’s ability to transfer key phosphate molecules to other proteins. This results in reduced duration of sleep.

Why the study matters

There are several adverse health effects associated with sleep deprivation, including early onset of conditions like Alzheimer’s and increased risk of heart disease.

However, people with this rare mutation can be fully rested even with fewer hours of sleep, compared to those who need a shut-eye of at least seven hours.

As per the researchers, short sleepers not only thrive on less sleep but may also feel “worse” if they sleep more.

“Our bodies continue to work when we go to bed,” detoxifying themselves and repairing damage, study co-author Ying-Hui Fu, a neuroscientist and geneticist at the University of California, San Francisco, told Nature. “These people [natural short sleepers], all these functions our bodies are doing while we are sleeping, they can just perform at a higher level than we can.”

Scientists hope the latest study will help them improve sleep quality and design better treatments for sleep disorders. “These findings advance our understanding of the genetic underpinnings of sleep,” scientists wrote, adding that it gives “further support for potential therapeutic strategies to enhance sleep efficiency”.

So, if you are a short sleeper, now you know why you have that superpower.

With inputs from agencies