Why You Shouldn’t Skimp on Sleep

All About Science

When life gets busy, sleep is often the first thing to go. But sleep is more important than you might think. Without proper sleep, your brain has trouble forming memories and learning new information.1 Chronic lack of sleep also takes its toll on your immune and cardiovascular systems.2 What’s more, most of us don’t get enough sleep on a regular basis.

Even though humans typically spend about one-third of their lives asleep, we still don’t know exactly why. What we do know is that sleep is a universal human need, and that without enough of it we face serious physiological consequences—both short- and long-term. Your mental health, physical health, productivity, and well-being are all affected by insufficient sleep. Chronic sleep loss can negatively affect your cardiovascular health and immunity, learning and memory, metabolism and body weight, energy and mood, and even your physical safety. Drowsy driving, for example, is estimated to be a factor in 328,000 car accidents annually.

Before modern sleep research began in the 1920s, scientists generally regarded sleep as a passive state in which the brain was inactive. Scientists have since discovered that, in fact, the brain can be more active during sleep than during waking hours! With the invention of EEGs (electroencephalograms), researchers could record the electrical patterns of brain activity during sleep and study the two main types of sleep.

What Happens When You Sleep

When we sleep, our bodies cycle through two alternating phases—REM (rapid eye movement) and NREM (non-rapid eye movement) sleep—both of which are important for different reasons.

REM sleep generally accounts for 20–25% of total sleep each night. It involves active dreaming, irregular respiration, and relaxation of the skeletal muscles. REM sleep is essential to our brain and mental health, processing and consolidating emotions, memories, and stress. It is also thought to stimulate the brain regions used in learning and developing new skills.

NREM sleep accounts for 75–80% of total sleep each night, and is the first phase of sleep each night in healthy people. It involves tissue growth and repair, energy restoration, and the release of hormones that are essential for growth and development. NREM sleep is divided into three stages, with each stage representing deeper sleep and slower brain waves.

REM and NREM sleep typically alternate in 90-minute cycles, approximately three to six times per night. If and when we don’t sleep enough, however, these cycles and the essential functions performed during these cycles are interrupted. Sleep deficiency can alter brain activity and make it harder to make decisions, solve problems, cope with change, control your emotions, and keep your mood up. It can also impact your blood pressure, blood sugar, body weight, immunity, reflexes, and reaction times.

So how much sleep is enough? The National Sleep Foundation recommends 7–9 hours of sleep each night for adults; 9–11 hours for school-age children; 8–10 hours for teenagers; and 7–8 hours for older adults.

Statistics show that many of us don’t sleep enough to meet these recommendations, unfortunately. Recent Gallup polls show 40% of American adults get less than seven hours of sleep a night (And perhaps not surprisingly, 43% say they would feel better if they got more sleep.). Younger adults say they get even less sleep: nearly half (46%) of 18- to 29-year olds reported that they sleep six or fewer hours a night.

Interestingly, this same survey in 1942 found that 84% of U.S. adults got at least seven hours of sleep each night, which means that as a society we’re now sleeping less overall. Sleep deprivation, it seems, has become a fact of modern life.

Healthy Sleep Habits

Since getting a good night’s sleep is essential to so many aspects of health, it makes sense that we prioritize sleep no matter how demanding our schedules get. In fact, prioritizing sleep really comes down to developing healthy sleep habits like these:

  1. Establish a consistent bedtime routine. Go to bed at the same time each night, and get up at the same time each morning, and stick to your routine even on the weekends. This will help you reset your circadian rhythm. Establishing a relaxing bedtime routine can help cue your body to start winding down. Try taking a warm bath or shower, reading, or enjoying a warm cup of herbal tea before turning in.
  2. Optimize your environment for sleep. Keep your room cool, between 60–67 degrees Fahrenheit, and as dark as possible. Darkness signals your brain to produce the melatonin that makes you sleepy and keeps you asleep. Use a sleep mask or blackout curtains to create your own darkness, and ban light-emitting gadgets and TVs from the bedroom, or at least shut them off a few hours before bed.
  3. Exercise daily. Physical exercise during the day is crucial to promoting good sleep at night. Getting some activity outdoors is even better, as exposure to natural light during the morning and midday can help regulate your sleep. Even a 10-minute walk can help if you feel pressed for time. But try to avoid exercising within a couple of hours of bedtime.
  4. Avoid stimulants before bed. Avoiding stimulants like caffeine or nicotine and even sugar after mid-afternoon can help. Avoid alcohol, too; while it may help you fall asleep initially, it can cause you to wake during the night. If you have any digestive issues, you might also want to avoid large meals or rich foods—which take longer to digest—before sleep.
  5. Try a natural sleep aid. If sleep still eludes you, consider taking melatonin to help you fall asleep. Known as the body’s natural sleep inducer, melatonin is a hormone secreted by your body’s pineal gland. Blood level concentrations of melatonin are at their highest in the middle of the night and are almost non-existent during the day.3

Good sleep habits are a crucial part of a healthy lifestyle—as important as eating a well-balanced diet, being active, maintaining meaningful relationships, and managing life’s inevitable stresses. There’s simply no substitute for a good night’s sleep, and not much (as the saying goes) that a good night’s sleep can’t fix.


1 Physiol Rev. 2013 Apr; 93(2): 681–766.

2  Pflugers Arch. 2012 Jan; 463(1): 121–137.

3 Curr Neuropharmacol. 2017 Apr; 15(3): 434–443.

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