The National Sleep Foundation recently issued new sleep guidelines, breaking down the numbers by age. However, individual sleep needs can vary within–or even outside–those parameters.
“We believe that individuals do have a basal sleep need, and if they were able to get the amount of sleep that they need and the quality of sleep that they need, this amount would remain relatively consistent,” says Natalie Dautovich, PhD, an assistant professor in the psychology department at the University of Alabama, Tuscaloosa, and environmental scholar with the National Sleep Foundation.
Your sleep needs varies based on a number of factors, including your genetics, illness or medical conditions, psychological or social stress, and any sleep deficiency. When you don’t get the sleep you need, you build up “sleep debt,” which requires you to get even more sleep to be fully rested.
But how can you know how much sleep is enough? Figuring out your perfect snooze time requires some sleuthing. Check out these key areas for clues.
If you’re not getting enough sleep, you’re typically not going to perform optimally, and may be more prone to mistakes and accidents, says Dr. Shalini Paruthi, fellow of the American Academy of Sleep Medicine (AASM) and the director of the Pediatric Sleep and Research Center at SSM Cardinal Glennon Children’s Medical Center in St. Louis. Are you noticing less-than-stellar or slower performance or a greater number of errors creeping into your work? Lack of sleep may be the culprit. But that can be tricky to assess in the moment, so it’s a good idea to look at periods where you struggled with performance and track your sleep levels during those times, she says.
“Having that hindsight of seeing how their performance and their productivity or relationships are is very important,” Paruthi says.
Grumpy? Flying off the handle? Depressed? Paying attention to your moods may give you insight into the amount of sleep you need, says Dautovich. If you feel energized and happy, chances are you’re getting enough sleep. Sleep affects every area of our mental and physical function, so if you’re groggy and impatient, you may need to adjust your sleep habits to give yourself more time under the blankets, she says.
When you’re going through stressful or demanding periods in your life, you may need to adjust your sleep length to better support your focus and performance. “If there is any psychological or social stress and then unfortunately those [sleep] needs may change,” Paruthi says.
When and how long do you sleep when you’re on vacation with no alarm clock? Think about a time when you had at least a week off. Did you sleep in every day? Did you wake early, but snooze for a half-hour in the afternoon? These are clues to your circadian rhythm and natural sleep patterns, Dautovich says. The next time you’re on vacation and not setting an alarm clock, see how long you sleep during a typical night.
“If you were waking up without an alarm clock over time, your sleep would stabilize, and you would determine how long you need to sleep and the timing of that sleep period naturally,” she says.
Another factor in the sleep equation is how long you typically take to fall asleep. Some people are highly efficient sleepers, falling asleep soon after hitting the pillow. Others take longer to hit that deep slumber and wake repeatedly during the night, Dautovich says. Sleeping for eight hours might not be enough if you aren’t an efficient sleeper, she says.
What about those reports of geniuses like Thomas Edison, who were reported to excel on multiple short periods of sleep instead of eight straight hours? “Polyphasic sleepers, the people who sleep for divided periods across a day or the very short sleepers, are very rare. And also unfortunately those sleep behaviors are just not really accepted or adaptive for our modern society,” Dautovich says.
That groggy feeling you may have upon waking is called sleep inertia, and it can be a sign that you’ve slept too little or, in some cases, too much, Paruthi says. Experts “don’t have a good explanation of why some people, if they sleep too long, actually feel more tired,” she says. It might be genetics, but paying attention to this feeling can help you calibrate the amount of sleep you need, she says.
Most of us get that post-lunch dip in energy, but if you’re groggy enough that your eyes are closing before close of business, it’s likely a sign that you need more sleep, whether at night or during a quick nap.
Like it or not, genetics play a big role in whether you need 7.5 or 9.2 hours of sleep, Paruthi says. Checking out your parents’ sleep patterns can yield useful insights. But use that information to inform and not dictate your sleep need research, since people’s sleep needs can change with age, she says.