Why Can Some People Function on Less Sleep? Genetics May Hold the Key

Ever wonder why some people wake up refreshed after just a few hours of sleep, while others can’t function without a full eight?

Take former British Prime Minister Margaret Thatcher—she famously slept only four hours a night, working late and rising early without missing a beat.

For the average person, though, that kind of routine would be a struggle. Most of us would feel sluggish, have trouble concentrating, and turn to caffeine or sugar just to get through the day.

So what explains this difference? It’s a question that’s intrigued researchers for years. Here’s what science has uncovered so far.

There’s a rare group of people known as natural short sleepers who need only four to six hours of sleep per night—and thrive on it throughout their lives.

Thriving on Less Sleep Without the Consequences

Unlike most people, they don’t feel fatigued, don’t rely on naps, and don’t experience the usual side effects of sleep deprivation. This unique ability is called the natural short sleep phenotype—a biological trait that enables them to gain the full benefits of sleep in less time.

In 2010, scientists identified genetic mutations linked to this phenomenon. These individuals carry uncommon gene variants that appear to make their sleep more efficient.

A 2025 study highlighted a woman in her 70s with one such mutation. Despite consistently sleeping just six hours a night, she remained in excellent physical health and mentally sharp—clearly adapted to a shorter sleep cycle.

Researchers are still exploring how prevalent these gene variants are and why they develop.

Chronic Sleep Deprivation Masquerading as a Rare Trait

But here’s the reality: most people who believe they’re natural short sleepers are actually just chronically sleep-deprived. Their limited sleep often stems from demanding work schedules, social obligations, or the mindset that less sleep equals greater productivity or toughness.

In today’s hustle culture, it’s not unusual to hear people proudly claim they get by on just a few hours of sleep. However, for the average person, this isn’t sustainable.

Over time, insufficient sleep leads to what’s known as “sleep debt”—a cumulative toll that can cause poor focus, irritability, brief involuntary naps (micro-sleeps), decreased performance, and serious long-term health risks.

Studies have linked chronic short sleep to higher chances of obesity, diabetes, high blood pressure, and cardiovascular conditions like heart disease and stroke.

To compensate for weekday sleep loss, many people attempt to “catch up” on rest over the weekend.

This strategy can help recover some short-term sleep debt. Studies indicate that adding an extra one to two hours of sleep on weekends or taking naps when possible may ease some of the harmful effects of limited sleep.

Still, it’s not a complete solution. Weekend recovery sleep and naps don’t always fully erase accumulated sleep debt, and the effectiveness of this approach is still debated among scientists.

In fact, a recent large-scale study found that weekend catch-up sleep may not counteract the cardiovascular risks tied to chronic sleep deprivation.

How Disrupting Your Sleep Schedule Can Backfire

Additionally, major shifts in sleep patterns—like sleeping in significantly on weekends—can throw off your internal body clock. This often makes it harder to fall asleep on Sunday night, leaving you less rested as the new workweek begins.

Growing research shows that repeated disruptions to sleep timing may have a greater impact on overall health and longevity than sleep duration alone.

In the end, while occasional catch-up sleep can provide some relief, it’s no replacement for maintaining consistent, high-quality sleep throughout the week. Still, achieving this kind of regularity can be especially tough for those with irregular schedules, such as shift workers.

Was She a True Short Sleeper or Just Catching Up on Rest?

It’s difficult to know for sure. Some accounts suggest she may have taken naps in the back of a car between meetings, which could indicate she was actually sleep-deprived and making up for lost rest whenever possible.

Regardless of whether someone is a natural short sleeper, many other factors can influence how much sleep a person needs. Age and underlying health conditions, for instance, play a significant role.

Older adults often experience shifts in their circadian rhythms and may have more disrupted sleep due to issues like arthritis or heart disease.

Ultimately, sleep needs vary widely between individuals. While a small number of people can truly thrive on less, most of us require seven to nine hours per night to function optimally. If you find yourself routinely cutting sleep short and relying on weekends to recover, it may be time to adjust your habits. Sleep isn’t optional—it’s a biological essential.

—Kelly Sansom, Research Associate, Flinders University & Murdoch University; Peter Eastwood, Deputy Vice Chancellor, Research and Innovation, Murdoch University (via The Conversation)

Read the original article on: Science Alert

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