II. The Basics of Adolescent Sleep Biology
“Sending kids to school at 7 a.m. is the equivalent of sending an adult to work at 4 in the morning[.] It’s almost abusive to them.” (179)—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.
In today’s society, persevering through tiredness is often considered a “badge of honour.” (180) Functioning while sleep deprived shows the ability to endure hardship. (181) “Historically, many members of the military view sleep as an indulgence; sleep deprivation in the interest of duty is even revered.” (182) Diminished sleep, however, is a stressor which may adversely affect the morale or psychological well-being of even highly-trained military personnel. (183) Adolescents represent a population far more vulnerable to the effects of restricted sleep. (2, 5, 6, 21, 29, 40, 53, 55, 59, 131) “[E]ven short-term sleep restriction has detrimental effects on the waking neurobehavioural functions of adolescents.” (147)
Most adolescents rise between 5 a.m. and 6:30 a.m. to meet the morning school bell, (25) essential training, some believe, for the “real world.” (184) While many adults in the “real world” start work early, many start considerably later than the average high school student. Recent census data reflect that 10.5 percent of Americans begin their morning commute between 8:00 a.m. and 8:29 a.m., with more than 27 percent leaving even later. (185) In major U.S. metropolitan areas, the median workday start time is 7:55 a.m. (185.5) In New York City, the world’s leading financial center, the median workday begins at 8:24 a.m., with 25 percent arriving by 7:28 a.m., and 75 percent by 9:32 a.m. (185.5)
College students may get underway even later. In the fall of 2010, for example, fewer than 2 percent of undergraduate courses at the University of Michigan started at 8:00 a.m. or earlier, and roughly 85 percent of classes started at 9:30 a.m. or later. (49) At Duke University, the earliest classes begin at 8:30 a.m. (186) Until reaching the age of majority, adolescents are judged as too young to vote, sit as jurors, or join the armed forces, but old enough to rise while much of the world is still sleeping.
The notion that early school scheduling might train students to rise before the sun is biologically unsound. (See, §§ II.B., III, infra.) “Forced awakening does not appear to reset the adolescent circadian rhythm and sleep lag is worse for earlier starting schools.” (343, Wahlstrom, Accommodating the Sleep Patterns of Adolescents Within Current Educational Structures: An Uncharted Path, publish. in, Adolescent Sleep Patterns, Biological, Social, and Psychological Influences (Carskadon, edit., Cambridge Univ. Press 2002) p. 174.) Paul Kelley, Ph.D., an honorary research associate at Oxford’s Sleep and Circadian Neuroscience Institute, explains:
“You can’t train your system to get up at a practical time. It’s biological, just as your heartbeat, your liver function and a bunch of other things that all sync to natural biological time and that is not in your control. [¶] Anything you do to change the rhythmic systems of your body means your organs become desynchronised with each other and this is where people get ill and there is no fixing it by giving someone an alarm clock. [¶] Your body is not watching your wristwatch.” (186.5)
In adults, shift work desynchronizes sleep cycles, resulting in sleep loss, and, in some instances, serious adverse health consequences. (187, 188, 189) The American College of Emergency Physicians reports:
“[T]he adverse effect of constantly rotating shifts is the single most important reason given for premature attrition from the field. The problems of rotating shifts stem mainly from working in opposition to the body’s normal circadian rhythms. The major circadian rhythm involved is the sleep/wake cycle.” (189.5, citation omitted.)
Sleep cycle disruption, a feature of early school start times, (2, 145) and the attendant restricted sleep, (20, 23) are similarly closely associated with serious health-risk consequences among adolescents, (190) except that these individuals are still developing, (2) their mortality/morbidity is increasingly implicated, (31, 46, 53, 120) and learning—ostensibly the primary purpose of education—is diminished. (2, 11, 13, 145)
“[S]leep is a highly complex state arising from an interaction between multiple brain regions, neurotransmitter pathways and hormones, none of which are exclusive to the generation of sleep. This complexity makes sleep very vulnerable to disruption. As a result, small changes in the brain during development can have a big impact upon sleep, and abnormal sleep will in turn feedback and impact upon health. This is what occurs as a consequence of abnormal sleep that arises from the systemic, chronic and unrecoverable sleep loss when education start times are too early.” (65)
The hour when the school day begins is the factor with the “greatest impact” on adolescent sleep sufficiency, (28) a point seldom considered (12) by those preparing students for the “real world.”
“For high school students (late adolescents), the single most important factor that determines [rise time] is their school start time; the length of their sleep cycle follows this variable closely[.] When students have more freedom to set bedtimes (vacations, weekends), most keep later bedtimes and also stay asleep for a longer duration[.] This is true for both high school students and college students[.]” (Thacher, Late Adolescence and Emerging Adulthood: A New Lens for Sleep Professionals, publish. in, The Oxford Handbook of Infant, Child, and Adolescent Sleep and Behavior (Wolfson & Montgomery-Downs, edits., Oxford Univ. Press 2013) p. 588, citations omitted.)
Professor of Neurology at the University of Minnesota Medical School and Medical Director of the Minnesota Regional Sleep Disorders Center, Mark Mahowald, explains the problem in plain terms:
“We’re sending them to school during the last one-third of their sleep cycles. It’s comparable to adults getting up at 3 a.m. or 4 a.m. You wouldn’t want to be making important decisions at that hour. I think it’s nuts. The sleep deficit builds up until they fall asleep at school or driving.” (20, italics added.)
As will be discussed, there are at least three significant biological factors to consider when evaluating the confluence of start times and adolescent sleep requirements: the essential/restorative value of sleep, (191, 192) adolescent circadian timing, (1, 103, 193) and the increased susceptibility in this population to the negative effects of sleep loss. (2, 5, 6, 21, 29, 40, 53, 55, 59, 131, 194)