Teens and Sleep Brain Science and Circadian Rhythms Sarah Raskin, PhD Department of Psychology and Neuroscience Program Trinity College Sarah.raskin@trincoll.edu Sleep is a biological requirement, as essential and valuable as good nutrition and exercise. It is an active process that energizes and restores your brain and body. Getting enough uninterrupted and restorative - or quality sleep - gives you the potential to thrive and makes it possible to live a full life. Sleep is essential to your ability to perform both cognitive and physical tasks at your peak and engage fully in life. While sleep needs and patterns change from childhood into adolescence and through adulthood, sleep still plays a vital role and contributes to every aspect of your development--physically, psychologically, emotionally, and socially.

Sleep Sleep is a behavior and an altered state of consciousness Sleep is associated with an urge to lie down for several hours in a quiet environment The nature of consciousness is changed during sleep We spend about a third of our lives in sleep Evidence supports the biological need for sleep Dualism-mind is separate from the body Descartes believed that the pineal body directed fluid from the ventricles into the holow fibers we call nerves-this induced muscle action. The pineal gland is where the soul controls the physical body Monism: the belief that the mind is the working of the body (no need for a separate soul. Determinism-the notion that mental states are produced by physical mechanisms. Reductionists-we break complex phenomena into less complicated sytems. 9.2

What is Sleep? A basic human drive regulated by two biological systems: Sleep/Wake Homeostasis The drive to sleep that increases the longer we are awake Circadian Rhythms The internal clock in our brain that regulates when we feel sleepy and when we are alert What is sleep and what do we know about it? Just like breathing and eating, we must sleep. It’s a basic human drive – a biological necessity and a physiological need - that must be met to survive.   Sleep is regulated by two biological systems: The Sleep/Wake Homeostasis drive to sleep becomes stronger the longer we are awake. After obtaining sufficient sleep, we will tend to be more alert; as the day goes on, the sleep/wake homeostasis drive increases our need to sleep. The Circadian Rhythm, or the internal clock in our brain that regulates our pattern or schedule of when we feel sleepy and when we are most alert, dips and rises over a 24-hour time period. The biggest dips occur during the time we need to sleep at night and then again, for a short period in the afternoon when you feel sleepy. During adolescence, the circadian rhythms shift later, which means many teens are sleepy well into the morning and experience a rise in alertness later in the evening, often until 11 pm. Keeping a regular sleep-wake schedule in accordance with these natural circadian rhythms helps promote healthy sleep.

Biological Rhythms Many of our behaviors display rhythmic variation SWS/REM cycles last about 90 minutes Daily rest-activity cycle is about 90 minutes Circadian rhythms (“about a day”) One cycle lasts about 24 hours (e.g. sleep-waking cycle) Light is an external cue that can set the circadian rhythm Some circadian rhythms are endogenous (do not require light) suggesting the existence of an internal (biological) clock Monthly rhythms Menstrual cycle Seasonal rhythms Aggression, sexual activity in male deer 9.4

Sleep Occurs in States and Stages We experience two alternating types or states of sleep: NREM sleep and REM sleep. The cycle repeats itself every 90 minutes. This slide shows you sleep architecture.   NREM or Non-Rapid Eye Movement includes 4 stages of sleep. As we shut our eyes for sleep, we first enter light sleep or Stage 1, the link between being awake and falling asleep. Stage 2 marks the actual onset of sleep, when you become disengaged from the environment, breathing and heart rate are regular and body temperature continues to go down. We spend about ½ of our sleep cycle in these first two stages. Stage 3 and 4 are the deepest stages of sleep. Muscles are completely relaxed, blood pressure drops and breathing is slower. During these deep stages of sleep, blood supply to the muscles is increased, energy is restored, tissue growth and repair occur and important hormones are released for growth and development. REM or Rapid-Eye Movement sleep occurs increasingly over the later part of the night and is also necessary for providing energy to our brain and body. During REM sleep, our brains are active and dreaming occurs. As we enter REM sleep, our bodies actually become immobile, muscles shut down, and again, we are relaxed. Breathing and heart rate may become irregular. During this stage the brain is active, and the eyes dart back and forth under the eyelids, giving REM sleep its name. Because getting enough REM sleep may contribute to memory consolidation, it is especially important following a learning experience. REM sleep typically comprises about ¼ of our night.

Why is Sleep Important Slow wave sleep may help restore and repair biological functions REM sleep may be required for: Vigilance Consolidation of Memories Brain Development Getting sleep helps prevent illness. Good sleep is associated with good health. Not only is sleep a basic biological requirement for optimum and safe performance, it is also essential for development and is particularly important during periods of brain maturation. Sleep can be considered food for the brain, since the brain is active during sleep. Also, the area of the brain – the prefrontal cortex – that is the last to develop and coordinates cognitive and emotional abilities, is particularly sensitive to sleep deprivation. Because both the brain and body are developing, that is probably why maturing children and adolescents need sleep, and when able, sleep more than adults. With a full night of consolidated sleep, alertness is renewed, and both learning and memory are enhanced.   As adolescents mature and form their perceptions of the world in many areas, they also adopt attitudes about sleep and establish sleep habits that may last a long time. Obviously, educators, parents and peers are influential and all play a role in establishing sleep-friendly homes and schools. They can make an important positive contribution toward teens’ sleep habits. And good sleep habits are key to their health – as important as good nutrition and regular exercise.

Sleep is Regulated by a Biological Clock in the Brain The internal mechanism that regulates when we feel sleepy and when we feel alert Resides in the brain and is affected by light and dark Melatonin Hormone secreted by the pineal gland during the dark phase of the day-night cycle The Circadian Biological Clock that regulates our 24-hour sleep-wake cycle resides in and is controlled by a group of cells in our hypothalamus called the Suprachiasmatic Nucleus or SCN.   From the optic nerve of the eye, light travels to the SCN, signaling the clock that it is light and daytime. When it is dark, we are driven to sleep and when it is light, we are alert. This clock knows “what time it is” by being synchronized with the eye’s exposure to light. The clock is like an orchestra conductor controlling the timing of body temperature and the secretion of several hormones.

Suprachiasmatic Nucleus (SCN) The SCN is primarily responsible for regulating the circadian rhythm, the body’s hard-wired internal ‘clock.’ Read Foster. Regulates body temperature, alertness, appetite, hormones and sleep patterns. Until a few decades ago it was believed humans had evolved past circadian entrainment.

During Sleep: Body temperature lowers Hormone levels rise and fall Changes in body temperature occur in accordance with the circadian clock and the sleep cycle. At night, before bedtime, the body’s temperature drops, making sleeping in a cool room conducive to sleep.   It is also important to allow enough time between exercise and bedtime for the body to cool down. The body also cools down after taking a warm bath, which in itself can be relaxing and help ease the transition into sleep.   During the sleep cycle, especially during the first part of the night when in deep sleep, critical hormones that are important to body functions and your health are released. These include: Growth hormone, which is released during the deep stages of sleep in the earlier part of the night. It is essential for growth and development and plays a role in muscle development and tissue repair. Sleeping long enough to allow secretion of growth hormone is important. Cortisol is often called the stress hormone because it is released when we are stressed. It is also released during sleep and increases over the night to promote alertness when it is time to wake up. Cortisol levels peak in the morning and dip to their lowest around bedtime. In response to light and dark signals entering the brain, the pineal gland—located in the base of the brain—produces melatonin. As night approaches and it becomes darker, melatonin is released and may help to induce sleep. During the teen years, its production tends to occur later in the evening. Getting a full night’s sleep provides enough time for all of these functions to occur and contribute to optimal health and performance. Thus, spending a little over 1/3 of your life in sleep provides you with what you need to function during the other approximate 2/3 of your waking life.

Teens Experience a Shift to a Later Sleep-Wake Cycle The biological clocks of children shift during adolescence, which drives them to a later bed time schedule (around 11:00 pm) and a natural tendency to wake later in the morning. This delayed phase syndrome can place them in conflict with their schedules – particularly early school start times. Contributing to the physical changes that occur as adolescence approaches, teens also experience a biological shift to a later sleep-wake cycle. Studies have found that, in teens, the sleep-inducing hormone melatonin is secreted later in the evening – around 11:00 pm – and also drops later in the morning. This sleep tendency to later times, often called a “delayed sleep phase syndrome,” puts teens into conflict with typical schedules, particularly early school start times.

Delayed Sleep Phase Sleep Schedule This slide shows what would be a natural sleep schedule for a teen. Many teens are physiologically not able to fall asleep before 11:00 pm. You can lie down earlier, but you might find it hard to actually fall asleep. After getting the 9 1/4 hours of sleep that you need in order to wake without an alarm clock or other intervention, a natural wake time would be around 8:00 am or so – again, putting you in conflict with earlier school start times. In order to get to school on time, many teens must wake before 6:30 am and shorten their sleep time.

The adolescent sleep pattern runs from about 11 p.m. to 8 a.m. and is “rather fixed.” Melatonin. Homeostatic pressure. Peak flow. Cortisol. Alert at 10 p.m. -- even after 14 hours wakefulness.

“ ‘Early to bed, early to rise’—may be difficult in the presence of a biologically driven phase preference.” ---Mary Carskadon, et al. (1993) Not a subject of dispute among scientists. Confirmed repeatedly. 1994 MMA letter.

“Sending kids to school at 7 a. m “Sending kids to school at 7 a.m. is the equivalent of sending an adult to work at 4 in the morning.” ---William Dement, M.D., Sc.D., Ph.D., Professor of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Division Chief, Stanford University Division of Sleep. Most rise between 5 a.m. and 6:30 a.m. on school days. If 7 a.m. = 4 a.m. Coddling. 30%. Duke. University of Michigan. Shift work – adverse health effects. Jet lag. Living out of sync with circadian rhythms. Circadian desynchronization.

Teens 85% of teens get less than the minimum requirement of 8 ½ hours of sleep Less Sleep ≠ More Time Shortened sleep impairs learning, performance, health and safety Teens are notoriously and chronically sleep-deprived--most adolescents do not get even their minimum requirement of sleep. According to research findings dating back to the 1970s, adolescents need on average 8 ½ to 9 ¼ hours of sleep to function at their best. In other words, as you enter puberty, the amount of sleep you needed as a child remains almost the same.   However, teens lead hectic 24/7 lifestyles. Not only does your lifestyle contribute to the amount of sleep you get--schedules, activities and social and academic pressures often result in poor and irregular sleep habits. Of course, a major demand in your life is to get to school on time and perform at your best so that you make the most of your learning experiences. Yet, many schools start early and teens are often awake before they can become alert in order to learn. Do you ever feel like a zombie in the morning, and wish you could put your head on a pillow and go back to sleep?. Getting less sleep does not give you more time to function at your best. Rather, shortened sleep leaves you sleepy throughout the day and not able to perform effectively. Not getting enough sleep can impair your learning, performance, health and safety. A significant outcome of sleep deprivation can be driving drowsy. According a study conducted in North Carolina, over ½ of fall asleep crashes involve young drivers. The 2000 NSF Sleep in America poll showed that when driving drowsy, 50% of young adults, 18-29 years of age, get impatient, 48% become stressed and 22% drive faster.

Consequences of Sleep Deprivation Cognitive, social and behavioral performance become impaired. Poor school performance and lower grades Tardiness and absence from school Difficulty remaining alert and paying attention Reduced ability to concentrate, problem-solve, remember and have a positive attitude More sports-related injuries More car accidents Sleep deprivation has serious consequences for persons of any age. Cognitive, social and behavioral performance is impaired and it takes more effort for teens to remain alert, concentrate, make decisions and achieve academically. In general, teens who have academic problems or report lower grades tend to sleep less and have irregular sleep patterns. Some of the recent memory studies indicate that during a good night’s sleep following a learning task, memory is consolidated and performance is improved as compared to those who get less sleep. Teens who do not get enough sleep also find it particularly difficult to pay attention during tedious, routine or boring tasks, and errors are more likely to be made.   Tardiness and absences are sometimes the result of having difficulty getting up in the morning. In NSF’s 2000 poll, approximately 38% of parents stated that it was somewhat to very difficult to get their adolescent up on school mornings.

Consequences of Sleep Deprivation, Cont. Excessive weight gain Elevated blood pressure Interference with secondary brain development Physical, psychological, or social difficulties

Consequences of Sleep Deprivation, cont. Increased criminality Increased caffeine consumption Increased health-risk behaviors: Cigarette use, Marijuana use, Alcohol use Feeling sad or hopeless Seriously considering attempting suicide 10% plus vs. 2.7%. Impaired judgment. Complete CDC list health-risk behaviors

Later Start Time Studies – Outcomes Kids get more sleep Fewer reports of depression Attention levels improve Less impulsivity ” Wolfson commentary on lost idealism. Dissent among parents and students turns to approval. 4 year study – kids got one hour more sleep than earlier starting peers across town. 5 hours more per week.

Later Start Time Studies – Outcomes, cont.: Higher attendance rates Higher graduation rates Fewer tardy students Fewer trips to the nurse’s office Students report feeling more motivated More hot breakfast meals consumed Administrators report greater “calmness” in the student body 1994 MMA letter. 50k students start times changed. 8:40 a.m. and 8:30 a.m. Minneapolis & Edina. 18k students studied over 4 year period.

Final Thought: Who is most affected? Some studies show that the rates of these effects are not universal But often those who are most affected are the most vulnerable—low income or low performing students Thus, we must ask not only are the effects widespread but even where they are not, do they effect the most vulnerable of our students

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