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Have you ever struggled to stay awake in your 9 a.m. class or early morning meeting, and wondered why? Let’s say you slept for six hours—below the recommended number, but you might think it would be enough to keep you functioning until you can grab a nap.

Not necessarily. How many hours you sleep matters, of course—a lot. But that’s not the only way sleep influences your functioning the next day (like being able to pick up where you left off in your thesis research, make a half-decent presentation at your quarterly meeting, and remember to wish your partner a happy birthday).

When you sleep may influence your academic performance even more than sleep duration does, research suggests. That’s because sleep isn’t just one experience affecting your body and brain; it’s a sequence of experiences that meet various physical, emotional, and intellectual needs. Combined, these stages are known as the sleep cycle. When you disrupt your sleep cycle, you’ll feel it, even if you’re getting the “right” total number of hours. Sleeping three hours at night and four in the afternoon, for example, is not equivalent to sleeping seven hours consecutively. (Also: The recommended number of hours for adults is 8–9 ¼, according to the National Sleep Foundation.)

Read a student story

“Greg,” a student at American University, DC, went to his doctor with sleep problems. In addition to being a student, Greg works 30+ hours per week and helps to care for his aging parents. Because of his competing priorities, Greg doesn’t usually fall asleep every night until around 3 a.m. and gets up at 8 a.m. for work at 9. He drinks coffee to stay awake and takes a 2-hour nap between work and class on most days. On weekends, he stays up late completing homework until 2 or 3 a.m., then sleeps until 1 p.m. Because of his hectic schedule, Greg hasn’t been feeling adequately rested and says he is on the verge of falling asleep in the office and during lectures.

Diagnosis  
Greg has a classic case of delayed sleep phase syndrome (DSPS). DSPS is seen in 17 percent of college students, and is characterized by a disconnect between sleep habits and societal demands, like getting up for school or work (“social jet lag”). Greg was not getting enough deep restorative sleep or REM sleep to function properly during the day.

“Students like Greg don’t have an underlying sleep disorder. They have poor sleep habits. If you take a nap for three hours a day, you are not going to be tired at 11 p.m. And with only five hours of sleep at night, you are interfering with the sleep cycle,” says Dr. Reitman. Even after sleeping for a few hours in the early evening, Greg will likely miss out on deep sleep and REM sleep.

Recommendation 
Here’s what Dr. Reitman suggests for students like Greg:

  • Avoid napping for longer than 30 minutes and/or late in the day.
  • Choose a specific sleep time and wake time and stick to it seven days a week (with 60 minutes leeway on the weekends for both sleep and wake time).
  • Limit computer use before bedtime.
  • Try melatonin, a dietary supplement, about two hours before sleep time; melatonin is a short-term sleep aid that may help reset the sleep cycle.

Are you sleep-deprived?

The University of Michigan Sleep Medicine Department identifies five warning signs:

  • Do you fall asleep in class or work?
  • Are your academics or work projects boring and not keeping you engaged?
  • Do you find it hard to concentrate?
  • Can you read or study for only a short time before your attention wanders?
  • Do you have a very hard time waking up in the morning?

Got sleep inertia?

We have all felt the pain of fragmented sleep after our night has been seriously interrupted. Our morning grogginess—also known as sleep inertia—is a liability. We cut ourselves shaving, we spill our coffee, we dump our adorable partner. Our memory, alertness, reaction time, and decision making are well below where we’d like them to be. Sleep inertia can last far longer than we might realize: two to four hours, according to researchers at Harvard Medical School. You’re likely to be less perceptive and attentive in class. You may struggle to understand why your male Spanish professor will never be embarazada. (It’s because this means pregnant, not embarrassed.) You may be irritable and not much fun to be around.

How about social jet lag?

If your natural wake time is routinely out of sync with the time that society (e.g., your class or work schedule) tells you to get up, you are likely suffering from social jet lag. In a 2000 study in the Journal of American College Health, students with an irregular sleep pattern performed worse academically than their peers, even when they slept the same total number of hours.

“For college students, the worst impact of inadequate sleep is the hit to their memory and learning,” says Dr. Shelley Hershner, a sleep specialist and assistant professor of neurology, University of Michigan. In a 2014 national survey, more than half of college students reported significant daytime sleepiness, and two in three felt sleepiness hurt their academic performance (American College Health Association’s National College Health Assessment). Sleep deprivation and disruption is among the top three causes of poor academic performance, along with stress and anxiety (which are also associated with disrupted sleep).

In studies, irregular sleep patterns, later bedtimes, and later wake-up times are associated with lower GPAs. Some evidence suggests that memory formation may be prompted by deep sleep (the third stage) and then consolidated by Rapid Eye Movement (REM) sleep, helping to explain why we need those sequential stages. “If you disrupt the natural sleep cycle, you will pay for it, either through being tired, getting poor grades, or even depression,” says Dr. David Reitman, medical director of the student health center at American University, DC.

What does sleep disruption do to us?

Not so smart after all: Memories of what you learned and experienced yesterday are consolidated during REM sleep. Deep sleep may also be involved in this process. Disrupted sleep means disrupted learning.

Difficulty with weight management: Sleep disruption affects the hormones that regulate hunger as well as our level of physical activity. Recurrent sleep deprivation increases our desire for high-calorie foods and may make us more prone to weight gain, research suggests. A 2006 study found that each hour of social jet lag was associated with a 33 percent higher risk of obesity.

Infections: Ongoing sleep deprivation and disruption are associated with weakened immune function, potentially leaving us less able to fight off viruses like the common cold.

Temptation to drink and smoke: Social jet lag is a risk factor for more than academic failure; it can also lead to increased use of alcohol, cigarettes, and caffeine, according to a 2006 study in Chronobiology International.

Accident-prone: Sleep-deprived drivers are less attentive, with slower reaction times and impaired judgment. In a 2010 study involving 1,039 undergraduates, one in six said they had fallen asleep while driving, according to the Journal of Adolescent Health.

Sexual slump: Sleep-deprived men and women report lower libidos and less interest in sex. In a 2015 study of college students, well-slept women had more sex than did tired women, according to the Journal of Sexual Medicine. In a 2011 study, ten male college students restricted their sleep to five hours a night for just one week, resulting in decreased testosterone; symptoms of testosterone deficiency include reduced libido, low energy, and difficulty concentrating.

Chronic disease and shortened life span: People who routinely get less than six hours of sleep a night are at increased risk of dying prematurely, according to a 2010 analysis of multiple studies in the journal Sleep. The less you sleep, the more likely you are to develop diabetes, obesity, and hypertension.

How to fix your sleep

The number-one sleep complaint of students is being tired, says Dr. David Reitman, medical director of the student health center at American University, DC. “Although some students do have underlying sleep disorders, 85 percent of tiredness is caused by poor sleep habits: too much caffeine, napping during the day, using cell phones, or being online late at night. All of these can interrupt your sleep, but they are all correctable habits.”

The key to sleeping well is synchronizing your sleep and wakefulness with natural darkness and light. This way, you can avoid sleep inertia and social jetlag. Here’s how:

  1. Avoid gadget use in the hour before you go to bed: Tablets, cell phones, and laptops emit light on a blue wavelength that suppresses melatonin, a hormone that helps control our sleep and wake cycles. In the evening, try a free light-dimming app that gradually dims your screen, like f.lux. If you can’t give up your tablet, make sure there’s no backlight. “Low instrumental music or white noise helps me fall asleep. There’s a great app called Dormio with many sound options,” says Laura B, a student at the Memorial University of Newfoundland.
  2. Try to get up the same time on the weekends as you do weekdays: Or at least keep your weekend lie-in to no more than an hour beyond your usual wake-up time. Waking up at a consistent time will help—a lot. Make plans with your friends or family to grab an early brunch or meet up with your running club in the morning. It’s harder to sleep in if you have to break plans.
  3. Get a hit of natural light first thing: Venturing outdoors in the morning helps regulates your body clock.
  4. Be physically active: For some people, exercising shortly before bedtime backfires; you may need to be active earlier to avoid sleep disruption.
  5. Nap strategically: Even brief naps can restore some memory function, according to the Journal of Sleep Research (2008). Up to 30 minutes is OK; longer or late naps will mess with your nights.
  6. Keep working on planning your assignments to avoid all-nighters: Even an hour or two of sleep is much better than nothing. Staying up all night is disruptive to your sleep cycle and learning—though you may not be aware of it. Students who stayed up all night performed worse on cognitive tasks, but figured their concentration and effort were just fine, according to a study in the Journal of American College Health.
  7. Avoid caffeinated drinks after 3 p.m.: Caffeine stimulates the brain and can cause insomnia, reducing your sleep duration and interfering with your sleep cycle.
  8. If you drink alcohol, keep it moderate; avoid cigarettes. Alcohol can help us get to sleep but reduces our deep sleep and REM sleep. Heavy smokers sleep lightly and don’t get enough REM sleep.
  9. Be cautious with sleep aids: Sleeping pills, such as Ambien and Lunesta, may put you to sleep a little sooner, but they don’t respect your sleep cycle. “They suppress REM sleep and also affect memory consolidation. I might give them to a student in crisis, but cognitive-behavior therapy has a 70–80 percent success rate for helping those who suffer from chronic insomnia and it does not interfere with the sleep cycle,” says Dr. Hershner. In 2013, the Food and Drug Administration (FDA) issued a safety alert for Ambien in response to research showing that some dosages led to excessive drowsiness the next day.

Do sleep apps help?

In general, your cell phone is the enemy of your sleep; texts and SnapChat are just too tempting. But your phone can perhaps be redeemed through the strategic use of an app that tracks your sleep and gives you feedback on your habits. Sleep doctors are divided on how useful these apps are; see what works for you.

Pros
“Sleep apps are evolving. They are getting better all the time. What they measure is activities related to sleep, such as movement in bed and whether you are snoring. The rise of sleep apps shows me that people are more aware and concerned about their sleep, and that’s a good thing. And one day we will have sleep apps that will really measure sleep (by evaluating brain activity).”
—Dr. Nathaniel Watson, president of the American Academy of Sleep Medicine (AASM); associate professor of neurology at the University of Washington; and codirector of the UW Medicine Sleep Center

Cons
“My patients bring in their cell phones or recordings of them snoring. Many are anxious because the app tells them they have a sleep disorder, or are relieved because they don’t think they have sleep apnea because the app says they don’t snore. To me, the results are pretty meaningless for diagnosis. And there are confounding factors [that can contribute to misleading results] if the patient doesn’t sleep alone or there is ambient noise.”
—Dr. Steven Park, assistant professor at the Department of Otorhinolaryngology—Head & Neck Surgery, Albert Einstein College of Medicine, New York; author of Sleep, Interrupted (Jodev Press, 2012)

Sleep Cycle Alarm Clock wakes you when you’re in your lightest stage of sleep.

SleepBot tracks your sleep and offers alarms and auto-settings for improving it.

Some fitness trackers can provide information on how you’re sleeping; the most popular include Basis, Jawbone’s Up app, and Fitbit.

Sleep Cycle Graph

Stage 1

  • 5–10 minutes; 2–5% of sleep time
  • Light sleep; you may drift in and out and be awakened fairly easily
  • Your brain waves become smaller, slower, and somewhat irregular
  • You might experience sudden muscle contractions preceded by a sensation of falling
  • If you wake up now, you may not even know you had been asleep

Stage 2

  • 40–50% of sleep time
  • Your body temperature starts to decrease
  • Your heart rate begins to slow
  • Your brain produces bursts of rapid, rhythmic activity
  • If you wake up now, you will not be startled; again, you might not even know you’d been asleep. But you won’t be getting to the deep sleep that should come next

Stage 3

  • 20% of sleep time
  • Delta waves in your brain put you into deep sleep
  • This is restorative sleep; it improves your immune function and your ability to repair damage caused by stress and ultraviolet rays
  • Deep sleep may determine your energy levels
  • You will move back into Stage 2 sleep before getting REM sleep
  • If you wake up now, it will be a struggle and you’ll feel disoriented

A single sleep cycle lasts 1 ½–2 hours. It involves three stages of Non-Rapid Eye Movement (NREM) sleep—including deep sleep (Stage 3)—and one stage of rapid eye movement (REM) sleep, in which our brains are most active, according to the American Academy of Sleep Medicine.

  • Visually, Stage 1 (light sleep) and REM sleep occupy the same band of this chart, but they are very different processes.
  • In a typical night you should get four to six full sleep cycles.

Learn more about REM sleep

REM sleep

  • 20 percent of sleep time
  • Occurs 90 minutes after you fall asleep
  • Your first REM stage lasts about 10 minutes; your final REM stage may last up to an hour—so if your sleep is fragmented, you’re likely missing out on the longer REM stages.
  • Your brain is very active; your heart rate and breathing quickens
  • You dream. Your voluntary muscle groups become temporarily paralyzed so you don’t act on your dreams
  • If you wake up now, you will probably remember your dreams. If you don’t get enough REM sleep, you’ll be sleepy the next day and have trouble handling stress. Your memory and verbal skills will be depleted, so you may take an academic and social hit.

SleepBot

by SleepBot

Joe Kasper

Martin Martinez: First-year undergraduate majoring in business administration at San Bernardino Valley College, California. Student Health 101 Student Advisory Board 2015–16.

“This app tracks your motion and sound trends while you sleep. If you wake up often and you feel tired then you can look at the graphs to see if there are external factors keeping you from resting.”

USEFUL?
I usually drink coffee in the mornings, but on the days I used the app, I didn’t have to rely on it.
Rating: 5/5

Fun?
I really liked going back to the app and looking at the sound and motion graphs.
Rating: 3.5/5

Effective?
Yes! I’m able to sleep 15 minutes more! #gettingmybeautysleepon
Rating: 5/5

+ Download on the AppStore

+ Get on Googleplay


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David Levine, MA, is a freelance medical and science writer based in New York City. He has written for Scientific American, New York Times, Good Housekeeping, Physician’s Weekly, and BioTechniques, among other publications.