How many hours a day should you sleep?

The question of how many hours of sleep are optimal for health and longevity is far more complex than often claimed. One of the most common recommendations—sleeping 8 hours a day—did not arise by chance. However, a study conducted in the early 2000s showed that this sleep duration may not be a universal norm. Some people who sleep 6–7 hours have better health indicators and even longer lifespans compared to those who regularly sleep 8 hours or more.

Modern scientific publications emphasize that the best sleep duration can vary for different age groups and individual physiological characteristics. According to the National Sleep Foundation (USA), adults typically need 7 to 9 hours of nighttime rest, but some people remain perfectly healthy with just 6 hours, while others require 9. The key factor is sleep quality and overall well-being throughout the day.

Professor Daniel Kripke’s Study

Professor Daniel Kripke of the University of California made a significant contribution to the discussion on sleep duration. In 2004, in the journal “Archives of General Psychiatry” of the American Medical Association, he published an article describing the results of a six-year study involving 1.1 million volunteers. The results showed that men and women who regularly slept less than eight hours (but no less than four) had higher survival rates compared to those who slept exactly 8 hours or more.

It is important to note that such studies only reflect statistical patterns and do not mean that those accustomed to 8-hour sleep and feeling great should necessarily change their habits. Scientists emphasize that sleep quality, overall health, and lifestyle—including diet, physical activity, the absence of bad habits, and a normal stress level—are of decisive importance.

Optimal Environment for Healthy Sleep

To ensure that 6–7 hours or any other optimal duration of sleep is restorative and high-quality, the following sleep conditions are recommended:

• A comfortable bed. A properly chosen mattress and pillow help maintain the spine in a physiologically correct position, promoting deep sleep without frequent awakenings.
• Optimal temperature. A comfortable range is typically considered to be between 16–20°C. Fresh and clean air in the bedroom contributes to better rest.
• Low noise levels. Loud sounds or sudden noises can cause frequent awakenings. If reducing noise levels is not possible, some people use earplugs or special white noise.
• Limited light exposure. Bright light, especially blue-toned light (such as from a smartphone screen), can negatively impact the production of the sleep hormone—melatonin. It is recommended either to completely darken the bedroom or use soft, dim lighting if orientation at night is necessary.
• A stable daily routine. Try to go to bed and wake up at the same time to establish natural circadian rhythms.

Interesting Facts About Sleep

Unusual Sleep Patterns of Great People

Leonardo da Vinci practiced polyphasic sleep: the great Italian scientist and artist slept in short 15-minute intervals every 4 hours.

Similarly, Albert Einstein (according to some sources) preferred brief naps throughout the day.

French philosopher Blaise Pascal spent much time in his bedroom, while Dr. Samuel Johnson, the famous lexicographer, rarely got up before noon.

Sleep and Longevity in the Animal World

Elephants, known for their long lifespans among mammals, sleep only about 2 hours a day.

Koalas, on the other hand, sleep up to 22 hours, yet their average lifespan in the wild is around 10 years.

Ants sleep only for a few minutes a day, organizing brief “naps” throughout the day.

Physiology of Sleep

An average person takes about 7 minutes to fall asleep.

People with normal healthy sleep sometimes wake up 15–35 times during the night, but most of these awakenings are so short that they are not remembered.

Reduction of Sleep Duration in the Modern Era

The average resident of the United Kingdom now sleeps 6–7 hours per day, which is 1–1.5 hours less than people slept in the early 20th century. In 1900, about 9 hours of nighttime sleep was considered normal.

According to some scientists, this reduction may be a consequence of industrialization, the spread of artificial lighting, and the overall increase in the pace of life.

Common Sleep Disorders

• Insomnia
• Severe snoring (which may be a sign of sleep apnea)
• Narcolepsy—episodes of uncontrollable daytime drowsiness
• Apnea—breathing interruptions during sleep, leading to reduced oxygen levels in the blood
• Restless legs syndrome (characterized by unpleasant sensations in the lower limbs and an urge to move them)

This is just a short list of the most common sleep disorders. In fact, medicine currently recognizes 84 types of sleep disorders.

In the United States alone, there are dozens of “sleep clinics” that specialize in these issues. Similar centers exist in many other countries.

Sleep and Road Safety

According to some experts, about 20% of all road accidents are related to drivers falling asleep at the wheel.

One of the more unusual methods to stay awake (described in some sources, though quite extreme) involves clamping a strand of hair in the car’s sunroof so that discomfort prevents dozing off.

Another tip is to eat an apple, as digestion stimulates the body and provides a more consistent release of energy than coffee. However, the most reliable method remains proper rest and stopping for sleep.

Sleeping Before Midnight

There is a popular belief that sleep before midnight is more beneficial than sleep after. There is no strict scientific confirmation of this theory, but research on circadian rhythms suggests that the best period for nighttime rest is usually between approximately 11:00 PM and 6:00 AM local solar time.

However, much depends on individual chronotypes: “early birds” wake up and go to bed early, while “night owls” may work productively late into the night and often go to sleep closer to or after midnight.

It is also known that as people age, their chronotype often shifts towards “early bird,” which is why teenagers and young people tend to be more like “night owls” compared to adults.

You can determine your chronotype with our online test: Find your chronotype: “early bird,” “night owl,” or “dove”.

Practical Recommendations for Healthy Sleep

1. Determine your chronotype. Observe at what time of day you feel the most energy boost. Adjust your daily schedule to make the most of your natural biorhythms.
2. Follow sleep hygiene. Include calming activities before bed (reading, quiet music, a warm shower), avoid bright light and electronic devices with high blue light emissions at least an hour before sleep.
3. Monitor your diet. Avoid overeating before bed and limit caffeine intake, especially after noon.
4. Analyze your overall health. If you regularly feel drowsy and fatigued even after 7–8 hours of sleep, this may indicate underlying health conditions. In such cases, it is recommended to consult a doctor or visit a specialized “sleep clinic.”
5. Learn to manage stress. High stress levels are one of the most common causes of insomnia. Use relaxation techniques, yoga, or meditation if you feel that tension is interfering with your sleep.

Sleep is a crucial component of a healthy lifestyle, and there are no strict “universal” rules regarding the exact number of hours required for everyone. The most optimal amount depends on age, health condition, physical activity level, and individual biorhythms.

Nevertheless, most experts agree that 6–9 hours of quality sleep per day is the golden mean for the majority of adults. The key is to listen to your body’s signals, maintain a healthy lifestyle, and seek professional help if persistent sleep problems or chronic fatigue occur.