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Source: American College Health Association. American College Health Association-National College Health Assessment: Arizona State University Spring 2019. Baltimore: American College Health Association; Spring 2019 (n=2,096).
How much sleep do I need?
Sleep needs differ among individuals and change with a variety of factors including age, mental and physical health and sleep debt. Within a 24-hour cycle, the average sleep needed is:
What causes sleep and wakefulness?
Sleep and wakefulness are caused by a two-part physiological system.
Each person’s body needs a specific amount of sleep to maintain health and to prevent feeling tired. A cluster of cells called the suprachiasmatic nuclei keeps careful track of the amount of sleep we get. If we need 8 hours of sleep, but only get 7 on a particular night, these cells register that we “owe” an additional hour of sleep. This is our sleep debt. The amount of sleep “owed” is added to the amount of sleep our suprachiasmatic nuclei wants us to have each night. In this example, we will need to get 9 hours of sleep tonight to make up for the 1 hour we missed last night.
Over time, we can build up a significant amount of sleep debt. For example, if our bodies need 9 hours of sleep, but we only get 6 hours Monday through Friday, we build up a sleep debt of 15 hours. When Saturday rolls around, we may try to “catch up on sleep,” but to do this we would need our nightly 9 hours, plus the 15 hours to “pay off” the sleep debt, thus bringing us to a sleep need of 24 hours. Most people are unable to sleep for this much time due to the alerting system of our brain. Even if we can get 12 hours of sleep, we will still be holding onto another 12 hours of sleep debt. This results in us still feeling tired after getting “a good night’s sleep.”
Researchers are not sure what happens to sleep debt in the long term (meaning sleep debt that has accumulated for more than a year). However, in the short term (6-12 months) the only way to feel less sleepy is to “pay back” the sleep that you have missed.
Night owls vs. morning larks
You may notice that you feel more energetic in the evening than you feel in the morning, or vice versa. You also many notice that this changes over time. While part of energy surge may be due to conditioning yourself to a certain lifestyle (for example, if you have to get up at 6 am for work, you may “learn” to be energetic in the morning), it is primarily due to a biological programming sleep researchers call The Night Owl/Morning Lark Process.
Night Owls have more energy and feel more awake in the evening. In fact, even if a Night Owl wakes up early and feels tired throughout the day, they generally experience a “second wind” in the evening, making it extremely difficult, if not impossible, for them to fall asleep early. Morning Larks have opposite experiences: they feel most energetic and awake in the morning and if they go to sleep late the night before, “sleeping in” is nearly impossible.
While it is still unknown exactly which part of the brain controls this, it has been determined that the process is biological. It also tends to change over time: children tend to have more energy and get sleepy earlier in the evening than adolescents, who can stay awake late into the night or early morning but have a very hard time waking up when their alarm goes off for school. In fact, because of school schedules and the Night Owl Process in high school and college students, these populations are believed to have the largest amount of sleep debt.
What influences sleep?
In addition to the biological aspects that control sleep and wakefulness, sleep can also be influenced by:
Alcohol - Studies show that alcohol may cause you to feel tired and fall asleep faster, but it prevents you from reaching deep sleep, thus preventing the restorative processes of sleep from occurring.
Physical Health - Illness and injury may cause you to feel tired and require more sleep to heal. However, pain or symptoms of illness can also distract our bodies from sleep.
Mental/emotional health - Feelings of worry, stress, depression, or anxiety may make our minds feel like they are racing and prevent us from sleeping. Excitement can have the same effect.
Environment - The physical surroundings of the place you are sleeping can affect your ability to sleep. This can include a roommate or partner’s sleep habits or snoring, outside noises, the temperature of the room and light.
Sleep disorders - While almost everyone experiences some kind of sleep abnormality once in a while (such as feeling worried and not being able to fall asleep), some people have a biological sleep pattern abnormality. These disorders include sleep apnea, insomnia, teeth-grinding, breathing disorders that present while sleeping such as snoring, narcolepsy, emotional disorders such as night terrors and nervous system disorders such as restless leg syndrome among others. If you suspect that you many have a sleep disorder it is important to get medical treatment.
Sleep is extremely important to a person’s overall state of health. When we get enough sleep, we are happier, healthier, more focused and significantly safer than we are when we are carrying around sleep debt. This is because, while we sleep, we turn off the more “active” physical processes of our bodies, such as moving and thinking and allow the passive processes, like cellular restoration, to take over. Some highlights of this restorative process include:
Tips for Restful Sleep
Take an online quiz/assessment and learn more about how sleep affects one’s health.
Examine your sleep debt by following these instructions:
STEP ONE: Calculate any sleep debt you may have.
If you are unsure of how much sleep you need each night, work with the average amount of 8 hours. This gives you an idea of your weekly sleep need (in this case, 56 hours). Think about how many hours, on average, you get each night of the week. If you get 6 hours Monday through Friday and 10 hours on Saturday and Sunday, you are getting 50 total hours of sleep. Subtract the amount of sleep you are getting from the amount of sleep you need, and that will give you an idea of your weekly sleep debt (in this example, 10 hours per week). Now estimate, in weeks, how long your sleep schedule has taken on this pattern. For the example, we’ll say this has been our sleep pattern for 2 weeks. Multiply the number of weeks by the hours of sleep debt, and that will give you an idea of the amount of sleep debt you have right now (for the example: 2 weeks x 10 hours of sleep debt=20 total hours of sleep debt).
STEP TWO: Identify if you are a morning lark or a night owl.
Think about when you have the most natural energy. If it’s during the morning, you are a Morning Lark. If it’s in the evening, you’re a Night Owl.
STEP THREE: Create a plan to “pay off” any sleep debt you may have.
The only way to “pay off” sleep debt is to make up the sleep that you missed and you may find that even making up a part of your overall sleep debt makes you feel significantly better. To do this, take into consideration the information you learned in steps one and two to figure out the best way for you to do this. How much extra sleep can you realistically get each night? Making up the entire 20 hours of sleep debt used in the example may be impossible in a single weekend; however, if you sleep 9 hours a night each night of the following week (rather than 8) by the end of the week you will have made up 13 of the 20 total hours “owed.” Also, keep in mind that, if you are a Morning Lark, you may find it easier to go to bed earlier than it is to sleep in later and if you are a Night Owl, you may find that the reverse is true.