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Have you ever struggled to stay awake in your 8 a.m. class and wondered why? Let’s say you slept for six hours—below the recommended number, but you think it might be enough to keep you functioning until your after-school emergency nap.

Not necessarily. How many hours you sleep matters, of course—a lot. The recommended number of hours for teens is 8–10, according to the National Sleep Foundation. But even though your six-hour snooze and your two-hour afternoon nap add up to eight hours, you still won’t feel well rested. Fragmented sleep is disruptive even if it adds up to a reasonable number of hours. It limits the deep restorative sleep and the REM sleep required for memory and learning enhancement.

But that’s not the only way sleep influences your functioning the next day. Getting enough uninterrupted sleep can help you power through pre-calc, put in a stellar performance at volleyball, and remember to wish your grandma a happy birthday.

1. Appetite is balanced

Sleep regulates the levels of hormones, such a ghrelin and leptin, that help with our feelings of hunger and fullness. Habitual sleep deprivation increases our desire for high-calorie foods and may make us more prone to weight gain, research suggests.

2. Muscle and tissue are repaired

During sleep, our body tissue repairs itself and growth hormone is released, which aids in muscle development and is responsible for things like growing taller. If you’re working out or playing sports, sleep is an important time for your muscles to repair so you can perform at your best.

3. Heart rate and blood pressure lower

During NREM (non-rapid eye movement) sleep, your heart rate and blood pressure slow down. The changes in blood pressure that happen throughout the stages of sleep seem to promote heart health, according to a 2011 report from the National Institutes of Health.

4. New connections are made

Participants showed a 33 percent increase in being able to establish and remember new connections after a full night’s sleep, as compared to people who had just learned the information, according to a 2007 study by researchers at Harvard Medical School. What this means in real life: If you learn a new skateboard trick, your brain will replay it during deep sleep, helping you remember it the next day.

5. Memories are solidified

The benefits to your memory are at their most significant when you sleep for eight hours in a row, according to a 2010 study published in Nature Reviews Neuroscience. This may actually help you store the information you learned about atoms and ions in chemistry class today, rather than forget it instantly.

Here’s what sleep disruption does to us

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

If your natural wake time is routinely out of sync with the time that society (e.g., your school schedule) tells you to get up, you are likely suffering from social jet lag. 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 published 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 sleep-deprived college students, one in six said they had fallen asleep while driving.

Chronic disease and shortened life span

People who routinely get fewer than six hours of sleep a night are at increased risk of dying prematurely, according to an analysis of 16 studies, published in the journal Sleep. Why? It may be because the less you sleep, the more likely you are to develop chronic diseases such as 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 in Washington 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. Here’s how:

PhoneAvoid 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, a student in St. John’s, Newfoundland and Labrador, Canada.

Coffee 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.

Alarm clockTry to get up at the same time on the weekends as you do weekdays. Or at least on the weekend try to get up no more than an hour beyond your usual wake-up time. Waking up at a consistent time will help—a lot. “It’s easier to get up when you make plans with friends for morning activities (breakfast, gym, etc.),” says John, a student in Ontario, Canada.

Bike Be physically active. For some people, exercising shortly before bedtime backfires; you may need to be active earlier to avoid sleep disruption.

Pillow Nap strategically.  Even brief naps can restore some memory function, according to a study in the Journal of Sleep Research (2008). Up to 30 minutes is OK; longer or late naps will mess with your nights.

Sunlight Take in some natural light first thing. Venturing outdoors in the morning helps regulate your body clock.

SleepKeep trying to plan your assignments so that you can 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 classic study by researchers at Bradley University in Illinois (1997).

Do sleep apps help?

In general, your cell phone is the enemy of your sleep; texts, Instagram, 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, which is when you’ll feel well-rested.

+ 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

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Article sources

Shelley Hershner, MD, sleep specialist and assistant professor of neurology, University of Michigan, Ann Arbor.

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David Reitman, MD, medical director, student health center, American University, Washington DC; adolescent medicine specialist and assistant professor of pediatrics at Georgetown University Hospital, Washington DC.

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Joanna Carmona is communications coordinator at the National Patient Safety Foundation. Previously, she was an assistant editor at Student Health 101. She has also edited collegiate textbooks for Cengage Learning and creating language learning materials for the US Department of Defense, libraries, and other educational institutions. Her BA in Spanish is from the University of New Hampshire.


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Lucy Berrington is a health writer, editor, and communications manager. Her work has been published in numerous publications in the US and UK. She has an MS in health communication from Tufts University School of Medicine, Massachusetts, and a BA from the University of Oxford, UK.