Have you ever noticed how some people bounce out of bed after just a few hours of sleep, while others can barely function without a solid eight hours?

Take Margaret Thatcher, for example. The former British prime minister was known for sleeping just four hours a night. She worked late, rose early, and seemed to thrive on little sleep.

But for most of us, that kind of sleep schedule would be disastrous. We’d be groggy, unfocused, and reaching for sugary snacks and caffeinated drinks by mid-morning.

So why do some people seem to need less sleep than others? It’s a question that’s fascinated scientists for years. Here’s what we know so far.

Natural short sleepers

There is a small group of people who don’t need much sleep. We call them natural short sleepers. They can function perfectly well on just four to six hours of sleep each night, often for their entire lives.

Generally they don’t feel tired, they don’t nap, and they don’t suffer the usual negative consequences of sleep deprivation. Scientists call this the natural short sleep phenotype – a biological trait that allows people to get all the benefits of sleep in less time.

In 2010 researchers discovered genetic mutations that help explain this phenomenon. Natural short sleepers carry rare variants in certain genes, which seem to make their sleep more efficient.

More recently, a 2025 study assessed a woman in her 70s with one of these rare mutations. Despite sleeping just six hours a night for most of her life, she remained physically healthy, mentally sharp, and led a full, active life. Her body, it seems, was simply wired to need less sleep.

We’re still learning about how common these genetic mutations are and why they occur.

Not everyone who sleeps less is a natural short sleeper

But here’s the catch: most people who think they’re natural short sleepers aren’t. They’re just chronically sleep-deprived. Often, their short sleep is due to long work hours, social commitments, or a belief sleeping less is a sign of strength or productivity.

In today’s hustle culture, it’s common to hear people boast about getting by on only a few hours of sleep. But for the average person, that’s not sustainable.

The effects of short sleep build up over time, creating what’s known as a “sleep debt”. This can lead to poor concentration, mood swings, micro-sleeps (brief lapses into sleep), reduced performance and even long-term health risks. For example, short sleep has been linked to an increased risk of obesity, diabetes, high blood pressure and cardiovascular disease (heart disease and stroke).

The weekend catch-up dilemma

To make up for lost sleep during the week, many people try to “catch up” on weekends.

This can help repay some of the sleep debt that has accumulated in the short term. Research suggests getting one to two extra hours of sleep on the weekend or taking naps when possible may help reduce the negative effects of short sleep.

However, it’s not a perfect fix. Weekend catch-up sleep and naps may not fully resolve sleep debt. The topic remains one of ongoing scientific debate.

A recent large study suggested weekend catch-up sleep may not offset the cardiovascular risks associated with chronic short sleep.

What’s more, large swings in sleep timing can disrupt your body’s internal clock, and sleeping in too much on weekends may make it harder to fall asleep on Sunday night, which can mean starting the working week less rested.

Increasing evidence indicates repeated cycles of irregular sleep may have an important influence on general health and the risk of early death, potentially even more so than how long we sleep for.

Ultimately, while moderate catch-up sleep might offer some benefits, it’s no substitute for consistent, high-quality sleep throughout the week. That said, maintaining such regularity can be particularly challenging for people with non-traditional schedules, such as shift workers.

So, was Thatcher a true natural short sleeper?

It’s hard to say. Some reports suggest she napped during the day in the back of a car between meetings. That could mean she was simply sleep-deprived and compensating for an accumulated sleep debt when she could.

Separate to whether someone is a natural short sleeper, there are a range of other reasons people may need more or less sleep than others. Factors such as age and underlying health conditions can significantly influence sleep requirements.

For example, older adults often experience changes in their circadian rhythms and are more likely to suffer from fragmented sleep due to conditions such as arthritis or cardiovascular disease.

Sleep needs vary from person to person, and while a lucky few can thrive on less, most of us need seven to nine hours a night to feel and function our best. If you’re regularly skimping on sleep and relying on weekends to catch up, it might be time to rethink your routine. After all, sleep isn’t a luxury – it’s a biological necessity.

Kelly Sansom, Research Associate, College of Medicine and Public Health, Flinders University; Research Associate, Centre for Healthy Ageing, Murdoch University and Peter Eastwood, Deputy Vice Chancellor, Research and Innovation, Murdoch University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

In July 2023, rising US basketball star Bronny James collapsed on the court during practice and was sent to hospital. The 18-year-old athlete, son of famous LA Lakers’ veteran LeBron James, had experienced a cardiac arrest.

Many media outlets incorrectly referred to the event as a “heart attack” or used the terms interchangeably.

A cardiac arrest and a heart attack are distinct yet overlapping concepts associated with the heart.

With some background in how the heart works, we can see how they differ and how they’re related.

Understanding the heart

The heart is a muscle that contracts to work as a pump. When it contracts it pushes blood – containing oxygen and nutrients – to all the tissues of our body.

For the heart muscle to work effectively as a pump, it needs to be fed its own blood supply, delivered by the coronary arteries. If these arteries are blocked, the heart muscle doesn’t get the blood it needs.

This can cause the heart muscle to become injured or die, and results in the heart not pumping properly.

Heart attack or cardiac arrest?

Simply put, a heart attack, technically known as a myocardial infarction, describes injury to, or death of, the heart muscle.

A cardiac arrest, sometimes called a sudden cardiac arrest, is when the heart stops beating, or put another way, stops working as an effective pump.

In other words, both relate to the heart not working as it should, but for different reasons. As we’ll see later, one can lead to the other.

Why do they happen? Who’s at risk?

Heart attacks typically result from blockages in the coronary arteries. Sometimes this is called coronary artery disease, but in Australia, we tend to refer to it as ischaemic heart disease.

The underlying cause in about 75% of people is a process called atherosclerosis. This is where fatty and fibrous tissue build up in the walls of the coronary arteries, forming a plaque. The plaque can block the blood vessel or, in some instances, lead to the formation of a blood clot.

Atherosclerosis is a long-term, stealthy process, with a number of risk factors that can sneak up on anyone. High blood pressure, high cholesterol, diet, diabetes, stress, and your genes have all been implicated in this plaque-building process.

Other causes of heart attacks include spasms of the coronary arteries (causing them to constrict), chest trauma, or anything else that reduces blood flow to the heart muscle.

Regardless of the cause, blocking or reducing the flow of blood through these pipes can result in the heart muscle not receiving enough oxygen and nutrients. So cells in the heart muscle can be injured or die.

But a cardiac arrest is the result of heartbeat irregularities, making it harder for the heart to pump blood effectively around the body. These heartbeat irregularities are generally due to electrical malfunctions in the heart. There are four distinct types:

• ventricular tachycardia: a rapid and abnormal heart rhythm in which the heartbeat is more than 100 beats per minute (normal adult, resting heart rate is generally 60-90 beats per minute). This fast heart rate prevents the heart from filling with blood and thus pumping adequately
• ventricular fibrillation: instead of regular beats, the heart quivers or “fibrillates”, resembling a bag of worms, resulting in an irregular heartbeat greater than 300 beats per minute
• pulseless electrical activity: arises when the heart muscle fails to generate sufficient pumping force after electrical stimulation, resulting in no pulse
• asystole: the classic flat-line heart rhythm you see in movies, indicating no electrical activity in the heart.

Cardiac arrest can arise from numerous underlying conditions, both heart-related and not, such as drowning, trauma, asphyxia, electrical shock and drug overdose. James’ cardiac arrest was attributed to a congenital heart defect, a heart condition he was born with.

But among the many causes of a cardiac arrest, ischaemic heart disease, such as a heart attack, stands out as the most common cause, accounting for 70% of all cases.

So how can a heart attack cause a cardiac arrest? You’ll remember that during a heart attack, heart muscle can be damaged or parts of it may die. This damaged or dead tissue can disrupt the heart’s ability to conduct electrical signals, increasing the risk of developing arrhythmias, possibly causing a cardiac arrest.

So while a heart attack is a common cause of cardiac arrest, a cardiac arrest generally does not cause a heart attack.

What do they look like?

Because a cardiac arrest results in the sudden loss of effective heart pumping, the most common signs and symptoms are a sudden loss of consciousness, absence of pulse or heartbeat, stopping of breathing, and pale or blue-tinged skin.

But the common signs and symptoms of a heart attack include chest pain or discomfort, which can show up in other regions of the body such as the arms, back, neck, jaw, or stomach. Also frequent are shortness of breath, nausea, light-headedness, looking pale, and sweating.

What’s the take-home message?

While both heart attack and cardiac arrest are disorders related to the heart, they differ in their mechanisms and outcomes.

A heart attack is like a blockage in the plumbing supplying water to a house. But a cardiac arrest is like an electrical malfunction in the house’s wiring.

Despite their different nature both conditions can have severe consequences and require immediate medical attention.

Michael Todorovic, Associate Professor of Medicine, Bond University and Matthew Barton, Senior lecturer, School of Nursing and Midwifery, Griffith University

This article is republished from The Conversation under a Creative Commons license. Read the original article.