How much sleep do you need?

External factors, not aging itself, lead to sleep loss in older adults

Though it is often believed that people need less sleep as they age, the recommended sleep guidelines for all adult age groups are almost identical. However, factors such as medication use, lack of physical activity, and loneliness can lead to sleep problems, and thereby lead older people to believe that they actually need less sleep than they do.

Forty to 110 minutes of deep sleep is recommended per night

Adults typically spend 10% to 20% of the night in deep sleep, also known as slow-wave sleep, with the rest of the night spent either in light sleep or REM states.

What sleep is for and why you can’t live without it

Sleep is one of the most important needs that humans have. The body uses sleep as a time of restoration and rejuvenation, as body tissues repair themselves, growth hormones are released, and the process continues. Brain plasticity theorists believe that sleep is also used for the processing and consolidating of new memories.

Studies suggest when you sleep is as important as how much you get, and syncing with your circadian rhythms may lead to less fatigue and improved long-term health outcomes

Humans may have evolved to need less sleep

Humans sleep less than most primates—but more efficiently. Chimps sleep 9.5 hours with 5% in REM, while humans get seven hours with 25% in REM. Some predict we may one day need just five hours, but for now, our sleep patterns balance rest and function, shaped by evolution and environmental stability.

Studies suggest when you sleep is as important as how much you get

"Molecular clocks" made of timekeeping proteins and genes help regulate the body and its processes, meaning the disruption of one cog will impact another. Those who live in sync with their circadian rhythms report less fatigue, clearer thoughts, greater medication benefits, and better long-term health outcomes.

Some animals seem to live well on little sleep

African bush elephants typically sleep for about 2 hours per 24-hour day, coming in well under a human's recommended seven-hour minimum. Other animals also appear to skimp on sleep, by human standards, without the consequences humans associate with being sleep deprived. This academic article details the sleeping habits of animals that appear to thrive on fewer than 40 winks and explores whether their sleep processes are just built different.

Sleep training: risks and benefits

Sleep training, which can range from implementing a nighttime routine to letting your baby cry it out, is controversial, but does it work? While dozens of studies have found sleep interventions to be effective, it appears that many of these studies...

Babies don't develop a circadian rhythm right away

Newborns don't develop circadian rhythm until they are a few months old, which helps to explain their erratic sleep schedules. When they're around three months old they begin to release melatonin, which influences sleep, and around the same time they develop more regular sleeping routines.

The evidence for the best sleep positions

For a behavior so crucial to human health, sleep positions are reportedly understudied by researchers. This article summarizes some of the more recent studies, taking into account the various forms of problems encountered during sleep: neck and back pain, snoring, acid reflux, and facial skin damage. Most studies point to side-sleeping as the most optimal, with sleeping on one's front as the least helpful. Read the piece to see which position is best for you.

For centuries, it was common to sleep in two shifts: a few hours at the beginning of the night, and a longer period beginning around midnight

Dangers of a record-breaking, sleep-skipping stunt

In 1963, 17-year-old Randy Gardner decided to stay awake for as long as it took to break the current world record. He managed to stay awake for 11 days. In 2017, the then-71-year-old Gardner told NPR that his experience had come back to haunt him as insomnia. The challenge has since been removed from the Guinness Book of World Records due to its dangerous consequences.

Chronological versus biological age

Science has come to understand different types of aging. What we call age is simply the number of years since birth, or chronological age. At the cellular level, biological aging happens at different rates for different people, and explains why some seem to age more quickly (or slowly).

The US loses roughly $400B a year in productivity due to sleep deprivation

For an article about a woman who built a business empire telling bedtime stories, the Hustle created this graphic showing the estimated GDP loss associated with chronic insomnia. The United States had a much more significant loss than other countries.

How to end bedtime procrastination

Finally done with external obligations, you might plop onto the sofa and dive into a hobby or bit of media, pushing past sleepiness to have some time to yourself and enjoy doing what you want. This is known as "revenge bedtime procrastination," a behavior that feels relaxing but impairs sleep hygiene.

How much water do humans really need to drink every day, and how food helps meet the quota

Because water is lost through breathing, sweating, urination, and bowel movements, consuming 2.0 to 3.7 liters (about 4.2 to 7.8 pint glasses) of water daily is recommended, depending on various factors, such as health conditions and exercise habits. Fruits and vegetables that are almost entirely water by weight, such as strawberries, cucumbers, and broccoli, can help increase water intake.

Health officials recommend at least 150 minutes of aerobic exercise per week

This official guideline from the CDC defines the baseline recommendation for healthy adult activity. These recommendations also emphasize that any movement is better than no movement, and that even short bursts of activity spread throughout the week benefit the mind and body.

Gibberish, urine, and utter chaos: what happens when you sleepwalk

Sleepwalking, or somnambulism, occurs most frequently in children who are in the deepest stages of sleep. REM, the sleep stage in which most people dream, often causes temporary muscle paralysis, so it’s only when sleepers pass to the deeper stages of sleep that sleepwalking—and sleep talking—can occur.

American Psychological Association issues recommendations for teen social media use

Listen to this three-minute podcast to learn more about the American Psychological Association's recommendations for teenagers' use of social media. The first report of its kind, it advises parents to closely monitor teens' social feeds during early adolescence, continually screen for signs of problematic use (such as sleep interference), minimize the amount of dangerous content their child is exposed to (such as disordered eating), and limit their teen's use of social media around appearance-related content.

Clinical insomnia is defined as trouble sleeping for three nights per week for at least one month

The term "insomnia" is often used in popular culture to refer to general difficulty sleeping or staying asleep. In the US, insomnia transitions to a clinical disorder when symptoms—dissatisfying, nonrestful, and life-disrupting sleep—occur at least three nights per week for at least one month and cause "clinically significant" distress in important areas of life.

A caffeine calculator

This simple calculator takes your preferred caffeinated drink and your body weight to determine how much is the right amount, and how much might kill you. In case you've ever had the morbid curiosity about just how much of that tea you'd have to drink to doze off forever. Find out your moderate and lethal doses here, as well as some extra info on caffeine consumption.

Children under 5 account for 76% of all malaria deaths in Africa

The main hypothesis for why the disease hits this age group the hardest is that children this young have still-developing immune systems. Pregnant women and people with HIV/AIDS are also at higher risk of severe infection.

Most adults don't need a daily vitamin, and it won't extend your life

A 20-year study by the National Cancer Institute involving almost 400,000 people found that daily multivitamins did not help people live longer. In some cases, these vitamins also increased the risk of death. Although some subpopulations—such as those with documented vitamin deficiencies and pregnant individuals—should take vitamins, daily multivitamins should not be taken uniformly by adults. Instead, patients should discuss vitamins with their clinicians and consider baseline vitamin testing before starting vitamin regimens.

Americans ages 30 to 34 have $44,800 in their 401(k) accounts on average

Americans ages 28 to 44 save about 13.5% of their pretax income on average, which is close to the recommended retirement savings rate of 15%.

Researchers believe the brain consolidates memories, processes emotions, and plans for the future during dream states

73% of people report they crave more physical touch in their lives

This figure came from a 2019 survey of 110 adults and examined what's formally called a "touch gap." Touch helps reduce stress, strengthening our immune system, and overall well-being. It can also improve children's health, adjustment, and IQ scores.

Certain vaccinations may be more effective when given around the middle of the day

A 2023 analysis of the health records of more than 1.5 million people in Israel suggests that COVID-19 vaccines may be more effective when received around the middle of the day. Separate early research also suggests there may be similar trends for influenza vaccines.

Brain death is a medical diagnosis without any wiggle room

Seeking to resolve long-standing variations between hospitals and state procedures, in 2023 several expert groups published comprehensive step-by-step guidance for clinicians to follow when determining brain death in kids and adults. Among other guidelines, it stated that doctors don't need to get family consent to do the tests needed to make this determination.

In recent years a child anxiety expert has created and tested a novel phobia and anxiety treatment approach for children, focused on changing how parents respond to the fears.

Use this calculator to find the dollar value of your mental load, from meal planning to coordinating after-school care for your children.

Children are now three times more likely to say they want to be a YouTuber when they grow up than an astronaut, with some even attending 'YouTube camps' that teach kids how to create content for the platform.

Bone marrow (soft tissue found inside certain bones) generates roughly 500 billion new blood cells each day

The first steps to rebuilding your credit score include getting to know exactly what's on your credit report and figuring out how far you are from the '700 club,' or 'good score' range.

Alzheimer's can lead to brain shrinkage, with an average of around 2% of volume reduction per year

Lesser-known phobias include turophobia, or the fear of cheese, and nomophobia, the fear of being without your cell phone.

Crows are believed to have intelligence on par with a seven-year-old child and demonstrate complex behaviors, from problem-solving with tools to recognizing human faces.

44% of Americans say they pray at least once a day—discover how your state's religiosity stacks up against the rest of the country.

Watch the cumbersome, but necessary, precautions healthcare workers must take to care for and protect themselves while caring for Ebola patients.

In 2026, Finland was named the world's happiest country for the ninth consecutive year based on its wealth, social safety network, and high life expectancy, among other factors.

The US Constitution is widely regarded as the longest-standing written national constitution still in force—see how it has influenced rights worldwide.

Coral polyps reproduce via broadcast spawning, where entire reefs simultaneously release reproductive cells for about one hour, once a year.

11 people died from firework injuries in the US in 2024.

Many legends about George Washington, including his supposed wooden teeth and the story of cutting down the cherry tree, lack evidence.

Scientists can determine Earth's past climate conditions by analyzing air trapped in microscopic bubbles within ice cores—columns of compressed snow layers that build up over hundreds of thousands of years.

The most expensive ad of all time was for Chanel No. 5 perfume and cost roughly $33M to produce in 2004—about $57M in today's dollars.

For centuries, Niagara Falls has been a magnet for daredevils seeking to conquer one of nature's most powerful wonders, with its 200-foot drop and water rushing at 32 feet per second with 280 tons of force.

Most of the observable universe's volume consists of voids and supervoids—enormous regions of space with little to no galaxies, stars, or light.

70 years ago today, city officials in Santa Cruz, California, banned rock 'n' roll to protect its youth from corruption after witnessing a 'provocative' concert the night before.

While El Niño moves warm Pacific Ocean waters east along the equator, La Niña moves them west, shifting where rainfall will become more common for months.

NBA superstar Victor Wembanyama spent the 2025 summer training with monks in central China to enhance his body and mind.