'Short Sleep:' How Losing Even a Little Rest Adds Up Over Time

We'll say it until the cows come home (or until the sheep retire under your eyelids): Sleep benefits your whole self and every element of your health. So how much can you get away with shaving off each night?

Problems involving sleep quantity or quality can take a toll: Active sleep deprivation can have an acute effect on your sense of reality, and poor sleep has longer-lasting health effects like prematurely aging skin, negative mood and heart disease. When we talk about sleep deprivation, the image that may pop to mind is that of a distressed, wild-haired person who slept two hours because they were up all night with a crying baby or studying for a final. 

What's maybe talked about less pointedly is the common phenomenon of short sleep, which the US Centers for Disease Control and Prevention describes as anything less than seven hours per night for adults. Importantly, your sleep doesn't have to be drastically short to have health effects. In fact, chronically restricting some sleep may less healthy, long-term, than the occasional all-nighter.

"'Short sleep' may be less extreme, but in a way it may be more problematic because people may not feel as urgently about changing this situation/behavior and end up with long term curtailed sleep," Jade Wu, a psychologist and sleep expert with Hatch, explained in an email.  

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What is short sleep? 

Most adults need between seven and eight hours per night, so technically, getting less than the low end of the sleep spectrum will put you in short sleep territory. According to the CDC, somewhere between 29% and 43% of US adults reported short sleeping in 2020. 

In real-life terms, this means you getting sixish hours most nights would put many people in short sleep territory. But like most things, there is some variation on what qualifies as short sleeping from person to person, Wu pointed out. 

"Some people need more sleep, and some less, so 'short' is a relative term that depends on a person's sleep need at this time," she said. For example, sleep needs can vary by age.

Short sleeper syndrome is a different thing

Short sleeper syndrome, or SSS, is the name given to the small group of adults that can healthily function on fewer than seven or eight hours of sleep each night without "feeling it." In recent years, researchers have toyed with the idea there may be genetic differences in those who can miss out on recommended sleep time without any apparent negative effects. 

But for the majority of people, short sleep comes with side effects you might be missing.

Read more: I Went to Bed With a Robot to Get Better Sleep. Here's Why You Should Too

Health effects of short sleeping 

Compared to acute sleep deprivation, where you're well aware you're in the throes of it and likely to make poor decisions or nod off early, long-term sleep deprivation or chronic short sleep may fly under your radar for a while if you're used to sleeping five to seven hours a night, for example, and occasionally catching up on the weekends.

Sleeping less than your body requires stresses it out, literally. Sleep deprivation affects your hormones and raises your cortisol levels, which has a negatively impact on your heart health. Insomnia, for example, has been linked to high blood pressure (often called the "silent killer" because it has no symptoms) and heart disease. 

One study from this year looked at the effects of "short sleep," about 6.2 hours per night, on women's blood sugar and insulin resistance, solidifying the potential connection between poor sleep and diabetes risk. Published in Diabetes Care, the study found that just six weeks of insufficient sleep or average short sleep interfered with insulin sensitivity, which interferes with blood sugar regulation.

Read more: How I Use Sleep Deprivation as a Productivity Tool, and Why That's a Terrible Idea 

Signs you're short sleeping 

If you're not sleeping enough because your work or home life priorities are putting you in a position where you feel you have to shave off a little shut-eye, chances are you already know it. But sometimes it's helpful to quantify exactly how much sleep you're getting, and you may turn to a sleep tracker, like Whoop, to detect a short sleep pattern. 

Other signs you're not sleeping enough include daytime drowsiness, becoming forgetful or mood effects like feeling irritable, anxious or on-edge.

Another sign your body is geared up on a short sleep pattern is that it doesn't take you long to fall asleep -- maybe under five minutes.

Read more: 27 Tips to Help You Sleep Better Tonight 

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Never too late to find a middle ground 

Perhaps one of the riskiest elements of short sleeping, or being mildly sleep deprived all the time, is that you may be able to keep it up for a while, potentially affecting your health gradually over time. And feeling just a little tired can affect other choices you make, like what to have for dinner and whether you have the energy to exercise, further compounding the negative effects of poor sleep.

But in the same way we emphasize improving nutrition, fitness and social health as part of a consistent lifelong goal to feel your best, there's always room for improvement and a chance to turn over a new sleep leaf. If you're not sure where to start, consider some tips for reducing your overall stress, turning to meditation and exercising during the day.   

"I think people and institutions are starting to really recognize the importance of sleep for every aspect of health and functioning," Wu said, adding that there's more investment in sleep as more people recognize that we're "safer and more productive" when well-rested. Sleep is also equalizing with other crucial elements of wellness, and was added to the American Heart Association's list of heart health essentials in 2022, she pointed out. 

If you've spent the last two years short sleeping, spend the next two ahead adding a little back each night. Slowly but surely, your body will thank you.

"I think that our bodies are so good at telling us what's important," Wu said, "as long as we actually listen."