Sometimes I hear the following concern: “I’m not getting eight hours of sleep each night.” I proceed to get a sense of this person’s sleep schedule and we realize he is getting about seven hours of sleep a night. He gives himself nine to 10 hours in bed each night to make sure that he can get his eight hours. He often lies awake for one to two hours in the middle of the night, feeling stressed about not getting enough sleep. He is worried about the health effects of insufficient sleep. He is specifically worried about some headlines that mention a connection between dementia and insufficient sleep. He says his sleep is refreshing and he doesn’t struggle with sleepiness during the day. How should someone approach this problem?
People in this situation have unfortunately been misled by the myth that everyone needs eight hours of sleep a night. I reassure him that there is nothing wrong with his sleep, he is not sleep deprived, and he therefore does not need to worry about health effects of sleep deprivation, such as heart disease, diabetes and dementia. I recommend he aim for seven hours of sleep a night, because that is all his body needs. How do I know that? Because he feels his sleep is refreshing, he does not struggle with sleepiness during the day, he does not rely on excessive amounts of stimulants like caffeine, and there is no indication for other health issues going on that would impact sleep.
The amount of sleep we need each night is a bit more complicated than saying everyone needs eight hours. Some people may need less and some more. It seems to be based on your genetics, but our understanding of the underlying cause is still lacking. If you look at 100 adults and determine how many hours of sleep each of them needs a night, most of the numbers will fall on a spectrum between seven and nine hours. It’s important to know where you fall on that spectrum so that you can plan your sleep schedule accordingly. But it’s not always static. Changes in certain habits, such as exercise, may lead you to need more than your usual hours of sleep. And we of course need more sleep when we’re sleep-deprived by a busy schedule.
There are some people who need less than that typical range of seven to nine hours. These natural short sleepers only need to sleep five to seven hours per night, and they also suffer none of the consequences of sleep deprivation. The research on the cause of this is limited, but some have been determined to have a specific genetic mutation that impacts their need for sleep. I have encountered many people who claim they are natural short sleepers. I often approach that with skepticism because it is very uncommon. It is more likely that someone claiming to be a short sleeper has a busy lifestyle that has led him to cope with chronic sleep deprivation with the help of caffeine and other forms of constant stimulation.
Being a long sleeper can be normal as well. However, it’s also important to make sure this is not indicative of a health problem. This is especially true if someone has only recently become a long sleeper. Many health issues can increase the hours of sleep you need. These include obstructive sleep apnea, pain medications, liver disease, heart failure, and many more.
The hours of sleep you need also decrease with age. Newborns can sleep 14 hours or more per day. The over-65 population needs an average of seven to hours of sleep each night.
Teenagers still need a lot of sleep, the spectrum being eight to 10 hours a night. That means a high schooler waking up at 7 a.m. during the week would need to be asleep somewhere between 9 p.m. and 11 p.m. the night before, depending on the amount of sleep he needs. However, it’s not as simple as setting and enforcing a regular bedtime. Our body clock changes during our teenage years to make us feel tired later at night and wake up later in the day. This is unrelated to behaviors and habits; it is considered innate. (However, I do fear that attachment to screens and addictive apps could be making our screenagers, I mean teenagers, delay their bedtimes even later than what is normal). This is part of the reason some states are enacting laws mandating high schools start no earlier than 8:30 a.m.. California was the first state to pass this law. A similar bill was introduced in the New Jersey Senate in May 2022, but there is no indication of when it will be voted on. Our society is starting to grapple with how one size does not fit all for how many hours of sleep we need, and at what time of the night we should get them.
I like to sum it up like this: The hours of sleep you need are the hours of sleep you need to feel awake and functional during the day. Your body will tell you as long as you are listening to it.
My next submission will finish up the three-part series on insomnia.
Bonus question: What was the typical sleep schedule hundreds of years ago, and how might that be reflected in certain Jewish customs and tefilot?
What sleep topic should I write about next? Send suggestions to [email protected]
David Rosen, MD, is a board-certified sleep medicine physician who is the co-founder and CEO of a digital health platform for simplified sleep apnea care called Renuma (www.renumasleep.com).
