How Many Hours of Sleep Do We Need?
Medically reviewed by Lauren Castiello, MS, AGNP-C
|Lauren is a board-certified adult-gerontology primary care nurse practitioner. Lauren has done NP clinical practicums focusing on the adolescent, adult, and geriatric populations in internal medicine, long-term care, and in outpatient oncology/bone marrow transplant. Lauren received a BA from Assumption University, a BSN from Massachusetts College of Pharmacy and Health Sciences, and her MS in Nursing from the University of Massachusetts at Lowell. She is certified by the American Academy of Nurse Practitioners (AANP).|
Sleep may just be the most important thing you do for your health. Without the proper amount of sleep, your body doesn’t have the chance to recover from your day and prepare for the next. While you’re asleep, your muscles repair themselves, your breathing and heart rate flexes as you go into REM sleep, and your immune system is recharged.
All of these things are in high gear while you sleep, and if you aren’t allowing your body enough hours to make all this happen, you’re putting yourself at a higher risk of getting sick and experiencing major health problems. Even if you’re a busy person, it’s important to make enough time for sleep each night. Adults need roughly seven to nine hours each night but let’s take a closer look at recommended hours of sleep by age group.
Recommended Hours of Sleep for Each Age Group
|Age||Hours of sleep needed per night|
|Ages 3-5||10-13 hours|
|Ages 6-12||9-12 hours|
|Ages 13-18||8-10 hours|
How Much Sleep Do You Need?
There are many factors to consider when it comes to recommended sleep you need each night. Ask yourself these questions to help determine how many hours of sleep you need.
- Do you expend a lot of energy in a day? If you do, you might need a little more sleep to recover from it. Consider closer to nine hours of sleep instead of seven so that you’re giving your body the proper amount of time to recharge from that much work.
- Do you consume a lot of caffeine? If you wake up groggy and in desperate need of that first cup of java, maybe you’re not sleeping enough and should consider increasing your sleep time by half an hour or more. If you’re already sleeping nine and still consuming a lot of caffeine, you might be overdoing it and hindering your sleep. In this case, try cutting back on caffeine to see if you can sleep better.
- Are you content with your level of alertness on a daily basis? If you are and you’re getting seven or even nine hours of sleep a night, then great! Keep doing what you’re doing.
- Do you have health concerns? Sleep can affect your health, and it’s important to get enough sleep. If you currently have any health issues or you’re at risk for any, make sure you’re getting at least seven hours of sleep per night, if not closer to nine. Rest is what helps your body recover and repair itself and fend off some further health issues.
What Is Deep Sleep? And How Much Do You Need?
Deep sleep, also known as “slow-wave” sleep, is the third sleep NREM sleep stage. It’s vital to memory recall and brain restoration. When deep sleep is not achieved, like in cases of insomnia, studies have found that participants cannot perform memory tasks as well as the average person. Generally, deep sleep should take up about 20% of the total time we are asleep. That’s about 1.5 to 1.8 hours of deep sleep each night. That’s not much time for something so important.
What does deep sleep do for the body? Put simply, deep sleep does a lot for the body. We need to go into a deep sleep each night to perform the best we can. It’s the chance for the brain to store new memories and recall information. Additionally, the pituitary glands secret the human growth hormone, which allows our tissues to grow and cells to regenerate.
You have to get enough deep sleep for all these vital bodily functions to take place. We know what you’re wondering, what happens if we don’t get enough deep sleep? In short, your mental and physical well-being will take a hit. Research has found tangible effects of not getting enough deep sleep.
More specifically, you’ll likely experience:
- You’ll have a hard time consolidating your memories.
- Retaining new information will be difficult.
- A higher risk of high blood pressure, heart attack, stroke, type 2 diabetes, and dementia.
- Chronic pain symptoms are exacerbated when you don’t get enough deep sleep.
- Impaired growth in children.
Here’s how to get more deep sleep
- Set aside time for sleep –– You want to follow the same sleep schedule as often as you can. Try and wake up and go to bed within the same 20-minute window each day.
- Exercise early in the day –– Working out late at night raises your heart rate and your body temperature, both of which will make it harder for you to fall asleep. You want to work out a few hours before bed at the latest.
- Change your diet –– Try to eat fewer carbs and make healthier diet choices. If you need to snack at night, opt for foods that will help you sleep.
Calculating Your Sleep Cycle
Because life happens, you may not be able to get the same amount of sleep every night. Maybe you’re up late doing homework or watching the big game on TV, but if, for whatever reason, you occasionally have a night of erratic sleep time, there’s a formula that will put your sleep cycle concerns to bed.
It’s based on getting either five or six cycles of sleep in for each night. Each sleep cycle includes four stages:
- N1: This includes the half-sleep that comes when you first go to bed through the first period of light sleep. It lasts 5-10 minutes.
- N2: This is light sleep that features a slower heart rate and shallower breathing, lasting roughly half an hour. Your muscles relax, and your brain waves also decrease.
- N3: Also called deep sleep, this lasts for less than an hour and is the time when your body heals and refreshes itself so that you can wake up energized and ready to go.
- REM: It stands for rapid eye movement. This stage lasts for up to an hour. During REM, your brain is quite active, and you may be dreaming. It’s named REM because your eyes may move back and forth rapidly under your closed lids.
Taken together, these four stages equal one sleep cycle, which should last around 90 minutes. You probably have a good sense of whether you need five cycles (7.5 hours of sleep) or six cycles (9 hours of sleep) a night.
Here’s the formula:
The time you go to bed + 15 minutes to fall asleep + 7.5 (five sleep cycles) or 9 (six sleep cycles) hours = the time you should wake up.
So, if John stays up to watch The Late Late Show and goes to bed at 1:00 a.m., and knows that he needs five sleep cycles to feel well-rested, then he should plan to wake up at about 8:45 a.m.
1:00 a.m. + 15 min. + 7.5 hours = 8:45 a.m.
It works the other way, too. Let’s say John has a presentation at work that means he needs to wake up at 6 a.m. Working backward, he should try to be in bed by 10:15 p.m. the night before.
6:00 a.m. – 15 min. – 7.5 hours = 10:15 p.m.
If John knew he needed six sleep cycles in order to be his best during the day, he would substitute 9 for the 7.5, which would have him waking up at 10:15 after watching The Late Late Show, while he’d need to get to sleep the night before his big presentation at an early 8:45 p.m
What Are the Symptoms of Sleep Deprivation?
Let’s be practical: Despite all your efforts, there will be days when you can’t get to bed as early as you should, as well as nights when you experience sleep deprivation and find yourself tossing and turning long after you should be asleep.
If that happens once in a while, it’s probably not a big deal. But if you consistently are getting inadequate sleep, you may experience some of the following symptoms:
Lack of alertness
If you’re tired, your reflexes are slower, your ability to perform is weaker, and you’re generally less on top of your game. It can also lead to an increased risk of car accidents, falls, and injuries.
A lack of sleep has been linked to obesity. There’s a correlation between not getting enough sleep and an increase in hormones that control hunger, leading to weight gain.
When you don’t have enough sleep, your emotions can get out of whack because your brain hasn’t had enough downtime to rest. Because you’re tired, you might experience mood swings, as well.
Feeling tired can increase stress, which in turn leads to anxiety. Conversely, sleep can quell anxiety because it gives your mind and body a break.
Serious health concerns
Linked to an increased risk of heart disease, diabetes, strokes, kidney disease, and high blood pressure. These can be exacerbated by the body not having enough time to rest and recover during sleep.
Spotlight on Shift Workers
Shift workers work long hours at unconventional times — think long-haul truckers or the night crew at your local hospital — and their hours may change from one week to the next. This makes for disturbed sleeping patterns. There’s even a name for it: shift work sleep disorder (SWSD), or circadian rhythm disorder, and it’s estimated that 10-40% of shift workers suffer from it.
Those with SWSD may have difficulty sleeping, or they may need to sleep more than is normal. They are more prone to accidents and can have a host of health-related issues, including cardiovascular problems. They also face a higher risk of addiction disorders.
If you suspect that you’re dealing with SWSD, consult your doctor on possible treatments. These may include medications, bright light therapy, and exercise. Although the best treatment is to avoid non-standard sleep hours, there are options available for those who do shift work to enable them to get enough sleep and live life to the fullest.
Making up for Lost Sleep
If you’re not engaged in shift work, it’s best to get the same number of hours of sleep every night, at roughly the same time. You have probably experienced the drowsiness that results, for example, if you normally sleep till 7:00 a.m. and one lazy Saturday stay in bed till noon. On the flip side, if you need to get up at 5:00 a.m. when you’re normally up at 7, you may also feel drowsy and want nothing more than to crawl back into bed.
This is called sleep debt, and it’s estimated that it will take you four days to recover for every hour of sleep you lose on a given night. So what should you do if you have a rough week at work or school and try to make it through the day on less sleep than is optimal? There are a few options.
- If you’re able to, a brief nap — no longer than 20-30 minutes — can help you get your balance back and ease drowsiness.
- When your time crunch is over, sleep a bit more than usual, but not more than two hours past the time you would normally wake up.
- Stay as consistent as possible otherwise with your sleep schedule so that your circadian rhythms have a chance to catch up with you.
So if you have been getting four hours of sleep a night for the past few days, compensate by going to bed 15 minutes early for several nights as soon as you can regain your normal routine, and sleep in a little — not a lot, just an hour or so — on Saturday.
This way, you are getting back some of the sleep you’ve lost but are not drastically changing your body’s circadian rhythms, which tell your body when to go to sleep and when to wake up. Also, make sure you are doing everything possible to create a comfortable setting for sleep, including finding the best mattress for your needs.
It’s important to get the proper amount of sleep each night because it’s crucial to your health. If you’ve wondered, “Is 6 hours of sleep enough?” the answer is no. It’s important to sleep the recommended amount as much as you can. If you find yourself not sleeping the recommended number of hours, see if you can rearrange your schedule to make the hours work. If you’re struggling to sleep enough each night, speak with your healthcare provider to find out a plan that will work for you to ensure you’re sleeping each night enough.
- Harvard Medical School: How Much Sleep Do We Really Need? By Anthony L. Komaroff, M.D. Published August, 2019. Accessed April 28, 2021.
- Mayo Clinic: How Many Hours of Sleep Are Enough For Good Health? By Eric J. Olson, M.D. Published June 6, 2019.
- Accessed April 28, 2021.Cleveland Clinic: How Much Sleep Do I Need? Author not listed. Published February 25, 2021. Accessed April 28, 2021.