The average American adult slept nine hours a night in 1910, according to the American Sleep Apnea Association. That average has dropped steadily ever since. Sleeptracker® data reveals that the average American now sleeps about six hours and 40 minutes.

While sleep tracking apps and mattress monitors are helping put sleep at the forefront of our minds, we’re still not getting enough. Before you can properly assess sleep performance, it’s important to understand what you should be aiming for.

What is Total Sleep?

Total Sleep Time (TST) refers to your total sleep episode minus awake time. In other words, total sleep is the number of hours you spend actually sleeping. Awake time includes the time it takes to fall asleep as well as those tosses and turns you make after a bad dream.

Total sleep influences your daytime sleepiness, physical performance, and mental acuity. Very short and very long total sleep times are associated with poorer working memory and verbal fluency, especially among adolescents. While you can’t judge sleep quality on length of sleep alone, it’s an indicator of sleep health.

REM Just Part of the Equation

We get the hype: it’s when you dream and form memories. These are exciting concepts, but there’s a lot more to sleep than rapid eye movement. So why does REM get so much attention? We spoke with Dr. Kristine Wilckens of the University of Pittsburgh’s Sleep and Chronobiology Center to find out.

“After sleep deprivation, the body makes up more time in REM sleep than it does in lighter stages of sleep,” Wilckens explained. But it’s actually a non-REM stage that helps us catch up most: slow-wave sleep is prioritized first, according to Wilckens. That’s why total sleep time is a stronger indication of sleep performance than any one stage. It includes all stages of sleep, each of which play a critical role in cognitive and physical function.

In fact, Wilckens supposes that REM and non-REM sleep “depend on one another.”

Let’s take a look at these stages in greater depth:

  • Light Sleep: Light sleep is the first, and most prevalent stage of sleep. Breathing and heart rate start to slow down, as muscles loosen and the body relaxes. You’re asleep but can wake without feeling disoriented.
  • Deep Sleep: As you drift further, you become less responsive to stimuli. Your brain is mostly at rest as your body restores and rebuilds. Deep sleep is also key for strengthening the immune system. This is the most restorative part of sleep, and the most difficult to wake up during.
  • REM Sleep: This is the part of sleep that’s most like being awake. Your eyes move, heart rate quickens, and breathing becomes more irregular. The mind is busy with learning, memory, and emotion regulation, as muscles enter a state of temporary paralysis. REM is, of course, when most dreaming occurs.  

According to Mark McCormick from FullPower Technologies, which collects and analyzes over 100 million nights of sleep data using machine learning, there’s no “most important” stage of sleep. He found that “it takes Ms. And Mr. Everyone 45 to 90 minutes to go through a complete sleep cycle.” If the cycle is not completed, “we will wake up groggy no matter how much REM sleep we got.”

Of course, we don’t spend an equal amount of time in each stage. The ASAA estimates that “three-fifths of a night’s sleep is light sleep, one-fifth is deep sleep, and one-fifth is REM sleep.” Typically, REM periods become increasingly longer and deeper with each cycle.

Setting Your Total Sleep Goal

So, while hitting each stage is important, total sleep is a more holistic measure. “The more time you spend sleeping, the more likely you are to progress into the deepest stage of non-REM sleep as well as REM sleep,” Wilckens pointed out.  

Factors like location, altitude, habits, gender, age, and culture can impact our sleep. McCormick has found that women tend to sleep 10 minutes more than men, Americans tend to sleep more than Europeans, and everyone tends to sleep more in the winter than the summer.

There isn’t a magic, one-size-fits-all number. “It’s a matter of balance between deep, light, and REM sleep,” he said. If you had to start somewhere, McCormick suggests seven and a half hours for women and seven hours and 15 minutes for men.

But before you set your own total sleep goal, consider your sleep efficiency (the ratio between total sleep time and time in bed). Dr. Wilckens recommends limiting awake time to less than 20 minutes. That means no Facebook scrolling, reading, or watching TV in bed – especially if you’re having a hard time falling or staying asleep.

After all, this is your wellness we’re talking about. It’s not about buzzwords; it’s about your body’s need to recharge so that you can perform at your best.