Plenty of scenarios might prompt you to wonder, “How much sleep do I need? No, seriously, exactly how many hours are required for me to be fully functioning but also not spend my whole life in bed?”
Maybe this thought arises as you start yet another true crime documentary when you should already be sleeping. Or perhaps you always want an afternoon nap even though you regularly clock eight hours. No matter why you’re wondering how many hours of sleep you need, we’re here to help.
Here’s how much sleep you need if you’re like most healthy adults.
Generally, people 18 to 65 function best on seven to nine hours of sleep a night, according to National Sleep Foundation (NSF) guidelines published in 2015. In the sleep medicine industry, these recommendations are usually seen as the definitive answer to the “How much sleep do I need?” question.
This advice is the result of a rigorous review of 312 studies by an interdisciplinary panel of 18 experts, including some of the foremost sleep experts in the country. For an all-encompassing look at sleep, the review also called upon experts from major medical organizations like the American Academy of Pediatrics, the American Congress of Obstetricians and Gynecologists, and the American Psychiatric Association. The goal of the review was to evaluate how much sleep is necessary for maximum physical, emotional, and mental health at different ages.
“Most [adults] really do function best when we get those magical seven to nine hours,” sleep doctor Carolina Marcus, M.D., an associate professor of clinical medicine in pulmonary diseases at the University of Rochester Medical Center, tells SELF.
Sleep needs for other age groups vary slightly. The NSF research divides people under 18 into six categories, each with different recommendations. For instance, newborns who are up to 3 months old require 14 to 17 hours of sleep every day. (What a life.) Adolescents 14 to 17 should get 8 to 10 nightly hours of rest. Then there are people over 65, who need seven to eight hours of sleep a night, according to the NSF.
So what if you need more or less than that?
A small group of people can regularly sleep more or less than recommended and be fine. These are what doctors often call short or long sleepers, Rajkumar Dasgupta, M.D., a clinician and associate professor at Keck Medicine of USC’s division of pulmonary, critical care, and sleep medicine, tells SELF.
For these individuals, sleeping more or less than recommended is not a sign of a health problem and does not negatively impact health, according to the NSF. This is why the NSF has established “possible acceptable hours” that are OK for some individuals, as well as “not recommended hours,” which don’t appear to be healthy for anyone.
For a select set of adults 18 to 64, six hours of rest every night can be enough, the NSF says. Don’t play yourself and try to get by on less than that. Fewer than six hours of sleep every night isn’t recommended for anyone in this age range.
The NSF divides the maximum appropriate upper sleep limit into smaller age increments. For adults 18 to 25, 10 to 11 hours may be appropriate, but more than 11 hours is not recommended. For adults 26 to 64, 10 hours may be appropriate, but that’s the cutoff, the NSF says. Regularly needing to sleep more than that can signal a health issue, which we’ll get to in a bit.
This is what determines how much sleep you need.
There are various reasons why you might feel excellent on seven hours of sleep or need every second of those nine hours. Genetics determine much of where you fall in this range, sleep psychiatrist S. Justin Thomas, Ph.D., director of the University of Alabama at Birmingham Behavioral Sleep Medicine Clinic, tells SELF.
A lot of scientific interest lies in other biological factors that can alter your sleep needs, like hormonal changes, Dr. Marcus says. The link between sleep and hormones is complex, according to the understatement of the century. Experts know a lot, like that the hormone melatonin helps to regulate sleep-wake patterns. But they are still determining to what extent hormone fluctuations that seem entirely disconnected from sleep may be involved. Take the menstrual cycle as an example. It seems as though related shifts in hormones like estrogen, progesterone, and serotonin may affect sleep, but a lot remains to be discovered.
The way your circadian rhythm (or internal clock) responds to the seasons is yet another biological element here, according to the NSF. Exposure to daylight helps to regulate your circadian rhythm, so you may notice that your sleep needs change a bit depending on the time of year. “A fair number of people do get more sleep in the winter and less sleep in the spring and summer when the daylight hours are longer,” Dr. Marcus says.
You may also be sabotaging your own sleep.
Various lifestyle factors can affect the quality of your sleep, which may then influence the quantity of sleep you need to feel well-rested, Thomas explains. If your sleep is constantly interrupted, it’s difficult for your brain to progress through the various phases of sleep you need to feel refreshed, Golam Motamedi, M.D., a neurologist at Georgetown University Medical Center, tells SELF.
Your caffeine and alcohol intake can be major players. Caffeine’s nature as a stimulant can obviously make it hard to fall asleep, but some evidence suggests that it may impact sleep quality even when you do doze off, Dr. Marcus says. As a central nervous system depressant, alcohol makes it easier to fall asleep—but once it wears off, you might become restless and wake up at night.
Your sleep hygiene has huge implications for how well you sleep (and, in turn, how much sleep you need). If you’re not doing things like sleeping in a cool enough room or blocking out enough light and sound, you might deal with constant sleep disruptions, which could make you feel like you require more hours of sleep.
Exercise is another habit that can impact how much sweet, sweet rest is right for you. People who train intensely, like athletes, may need more sleep to assist with muscle reparation and growth, Dr. Motamedi says.
Then there are lifestyle factors such as daytime napping and shift work that can interrupt your body’s sleep-wake patterns, triggering or perpetuating insomnia, according to the NSF.
Some health conditions impact sleep, too.
Below, you’ll find a few of the most common health conditions that can affect your sleep. Keep in mind that anything that makes falling or staying asleep difficult can make it hard to get sufficient quality sleep.
Anxiety and depression: While depression can make it difficult to sleep, it can also cause some people to sleep more than usual, according to the National Institute of Mental Health (NIMH). This can also happen with other mental health conditions that can include depressive episodes, such as bipolar disorder. Similarly, the racing thoughts that come with anxiety can impact your sleep, too. Some people even experience nocturnal panic attacks, or overwhelming bouts of fear that rouse them from sleep.
Both of these issues can become cyclical, with insomnia worsening anxiety or depression and vice versa.
Gastroesophageal reflux disease (GERD): This is acid reflux (when your stomach acid flows up into your esophagus) on steroids. If you have mild acid reflux at least twice a week or moderate to severe acid reflux at least once a week, that qualifies as GERD, according to the Mayo Clinic.
Most people with this GI disorder see its major symptoms, like heartburn, intensify when they lie down (like when they try to sleep), according to the NSF. If the acid reaches your throat, you can reflexively wake up coughing and choking.
Idiopathic insomnia: You might think insomnia only prevents people from falling asleep, but insomnia can also make staying asleep feel nearly impossible. While underlying issues like various health conditions may cause what’s known as secondary insomnia (or insomnia that has a specific cause), some people have primary (or idiopathic) insomnia, meaning there is no apparent cause behind their sleep issues.
Obstructive sleep apnea (OSA): OSA is the most common type of sleep apnea, which is when your breathing stops and starts as you sleep, according to the Mayo Clinic. It occurs when muscles at the back of your throat intermittently relax too much and block your airway. Sensing this lack of oxygen, your brain arouses you from sleep to correct your breathing, so you might wake up gasping for air.
“Even if someone with obstructive sleep apnea gets seven to nine hours, they may not ever get to that deep sleep that is so refreshing, and so they wake up feeling very tired,” Dr. Motamedi says.
Pain: It can be difficult for somebody distracted by pain to fall asleep, stay asleep, and remain comfortable in bed for hours, Thomas says. Conditions that can cause this include arthritis, fibromyalgia, migraines, and multiple sclerosis, as well as temporary pain issues like an injury or nighttime discomfort involved with pregnancy.
Anemia: If you have anemia, your body does not have enough healthy red blood cells to bring oxygen to all your tissues so they can function properly, per the Mayo Clinic. This can cause exhaustion and weakness that make it hard to live life normally.
Chronic fatigue syndrome: The chief characteristic of this complicated and poorly understood disorder is, as you may have deduced, extreme fatigue that is not caused by an underlying medical condition and does not abate with rest, according to the Mayo Clinic. Other symptoms include memory problems, concentration issues, and headaches.
Hypothyroidism: In this condition, a deficiency of thyroid hormones causes a slowing of metabolism, which governs how your body uses energy. Incessant fatigue is one common result, according to the Mayo Clinic.
What to do if you frequently sleep more or less than recommended.
We’d consider seeing a doctor if this describes you. A primary care doctor can review your sleep habits, discuss sleep hygiene, and screen you for various health conditions. They can also refer you to a specialist if necessary.
Before your next appointment, it may help to keep a sleep diary for a couple of weeks, Dr. Dasgupta says. (Here’s a handy one from the NSF.) Track how long you’re sleeping, if you’re waking up at night, and how you feel in the morning, along with habits that you suspect may be affecting your sleep.
Even if you can’t pinpoint the issue yourself, doing this may give your doctor some insight into how to fix any critical sleep problems you have. As Dr. Dasgupta says, “Those eight or so hours at night really contribute to your health during the day.”