How Many Hours of Sleep Do You Need?
The amount of sleep a person needs depends on many things, including their age. In general:
- Infants (ages 0-3 months) need 14-17 hours a day.
- Infants (ages 4-11 months) need 12-15 hours a day
- Toddlers (ages 1-2 years) need about 11-14 hours a day.
- Preschool children (ages 3-5) need 10-13 hours a day.
- School-age children (ages 6-13) need 9-11 hours a day.
- Teenagers (ages 14-17) need about 8-10 hours each day.
- Most adults need 7 to 9 hours, although some people may need as few as 6 hours or as many as 10 hours of sleep each day.
- Older adults (ages 65 and older) need 7-8 hours of sleep each day.
- Women in the first 3 months of pregnancy often need several more hours of sleep than usual.
But experts say that if you feel drowsy during the day, even during boring activities, you haven't had enough sleep.
Sleep Deprivation and Sleep Debt
The amount of sleep a person needs goes up if they’ve missed sleep in previous days. If you don’t have enough, you’ll have a "sleep debt," which is much like being overdrawn at a bank. Eventually, your body will demand that you start to repay the debt.
We don't really adapt to getting less sleep than we need. We may get used to a schedule that keeps us from getting enough sleep, but our judgment, reaction time, and other functions will still be off.
Why You Need REM Sleep and Deep Sleep
There are four stages of sleep, based on how active your brain is. The first two are light.
Stage three is “deep sleep,” when your brain waves slow down and it’s harder for you to wake up. During these periods, your body repairs tissues, works on growth and development, boosts your immune system, and builds up energy for the next day.
Rapid eye movement (REM) sleep or stage R usually starts about 90 minutes after you fall asleep. Brain activity increases, your eyes dart around quickly, and your pulse, blood pressure, and breathing speed up. This is also when you do most of your dreaming.
REM sleep is important for learning and memory. It’s when your brain handles information you’ve taken in during the day and stores it in your long-term memory.
Signs of Sleep Deprivation
Common signs that you haven’t gotten enough sleep include:
- Feeling drowsy or falling asleep during the day, especially during calm activities like sitting in a movie theater or driving
- Falling asleep within 5 minutes of lying down
- Short periods of sleep during waking hours (microsleeps)
- Needing an alarm clock to wake up on time every day
- Feeling groggy when you wake up in the morning or throughout the day (sleep inertia)
- Having a hard time getting out of bed every day
- Mood changes
- Trouble focusing on a task
- Sleeping more on days when you don’t have to get up at a certain time
How to Know if You’re Getting Enough Sleep
To find out whether you’re getting enough sleep at night, ask yourself:
- Do you feel healthy and happy on your current sleep schedule?
- Do you feel like you get enough sleep to be productive?
- Do you ever feel sleepy when going about your day?
- Do you rely on caffeine to get through the day?
- Is your sleep schedule fairly regular, even on weekends?
The Effects of Sleep Deprivation
Too little sleep can cause:
- Memory problems
- Feelings of depression
- Lack of motivation
- Slower reaction times
- A weakened immune system, raising your chances of getting sick
- Stronger feelings of pain
- Higher chances of conditions like high blood pressure, diabetes, heart attack, or obesity
- A lower sex drive
- Wrinkled skin and dark circles under your eyes
- Overeating and weight gain
- Trouble solving problems and making decisions
- Bad decision-making
Studies make it clear that sleep deprivation is dangerous. People who missed some sleep before getting into a driving simulator or doing a hand-eye coordination task perform as badly as or worse than people who had been given alcohol.
Sleep deprivation also changes how alcohol affects your body. If you drink while you’re tired, you’ll be more impaired than somebody who got enough rest.
Driver fatigue caused about 83,000 car accidents between 2005 and 2009 and 803 deaths in 2016, according to the National Highway Traffic Safety Administration.
Some researchers say the numbers are actually much higher. Since drowsiness is the brain's last step before falling asleep, driving while drowsy can -- and often does -- lead to disaster. Stimulants like caffeine can’t stop the effects of severe sleep deprivation.
The National Sleep Foundation says you’re probably too drowsy to drive safely if you:
- Have trouble keeping your eyes focused
- Can't stop yawning
- Can't remember driving the past few miles
- Are daydreaming and have wandering thoughts
- Have trouble holding your head up
- Are drifting in and out of lanes
How to Get the Sleep You Need
Healthy habits can help you sleep better and longer.
- Give yourself time to sleep. A busy schedule can make it hard to get a good night’s sleep.
- Keep a sleep schedule. Go to bed and get up at the same time every day, even on weekends.
- Create a sleep sanctuary. Keep your bedroom dark, quiet, and at a comfortable temperature. Use it only for sleep, sex, and quiet activities like reading. Don’t bring in electronic screens like TVs or cell phones.
- Have a bedtime routine. Avoid bright lights, large meals, caffeine, and alcohol before bed. Try things to help you relax, like a hot bath.
- Exercise. Get about 30 minutes a day, at least 5 hours before bed.
- Nap if you must. Aim for no more than 30 minutes so you don’t wake up groggy or mess up your sleep schedule.
- Talk to your doctor. A medical condition might be causing your sleep problems.