Why We Sleep

Figure 11: NBA Player Performance
More than Eight Hours Sleep vs. Less than Eight Hours Sleep

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Of course, most of us do not play for professional sports teams. But many of us
are  physically  active  throughout  life  and  constantly  acquiring  new  skills.  Motor
learning and general physicality remain part of our lives, from the banal (learning
to  type  on  a  slightly  new  laptop  or  text  on  a  different-size  smartphone)  to  the
essential, such as experienced surgeons learning a new endoscopic procedure or
pilots learning to fly different or new aircraft. And so, therefore, we continue to
need  and  rely  upon  our  NREM  sleep  for  refining  and  maintaining  those  motor
movements.  Of  interest  to  parents,  the  most  dramatic  time  of  skilled  motor
learning  in  any  human’s  life  occurs  in  the  first  years  after  birth,  as  we  start  to
stand and walk. It is of little surprise that we see a spike in stage 2 NREM sleep,
including sleep spindles, right around the infant’s time of transition from crawling
to walking.
Returning  full  circle  to  that  which  I  had  learned  years  ago  at  the  Queen’s
Medical Center regarding brain damage, we have now discovered that the slow,
day-by-day return of motor function in stroke patients is due, in part, to the hard
night-by-night work of sleep. Following a stroke, the brain begins to reconfigure
those  neural  connections  that  remain,  and  sprout  new  connections  around  the
damaged  zone.  This  plastic  reorganization  and  the  genesis  of  new  connections
underlie the return of some degree of motor function. We now have preliminary

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evidence  that  sleep  is  one  critical  ingredient  assisting  in  this  neural  recovery
effort.  Ongoing  sleep  quality  predicts  the  gradual  return  of  motor  function,  and
further determines the relearning of numerous movement skills.
XIII
Should more
such  findings  emerge,  then  a  more  concerted  effort  to  prioritize  sleep  as  a
therapeutic aid in patients who have suffered brain damage may be warranted, or
even  the  implementation  of  sleep-stimulation  methods  like  those  described
earlier. There is much that sleep can do that we in medicine currently cannot. So
long  as  the  scientific  evidence  justifies  it,  we  should  make  use  of  the  powerful
health tool that sleep represents in making our patients well.
SLEEP FOR CREATIVITY
A  final  benefit  of  sleep  for  memory  is  arguably  the  most  remarkable  of  all:
creativity.  Sleep  provides  a  nighttime  theater  in  which  your  brain  tests  out  and
builds connections between vast stores of information. This task is accomplished
using  a  bizarre  algorithm  that  is  biased  toward  seeking  out  the  most  distant,
nonobvious  associations,  rather  like  a  backward  Google  search.  In  ways  your
waking  brain  would  never  attempt,  the  sleeping  brain  fuses  together  disparate
sets of knowledge that foster impressive problem-solving abilities. If you ponder
the  type  of  conscious  experience  such  outlandish  memory  blending  would
produce, you may not be surprised to learn that it happens during the dreaming
state—REM sleep. We will fully explore all of the advantages of REM sleep in the
later chapter on dreaming. For now, I will simply tell you that such informational
alchemy conjured by REM-sleep dreaming has led to some of the greatest feats of
transformative thinking in the history of the human race.

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CHAPTER 7

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Too Extreme for the Guinness Book of World Records
Sleep Deprivation and the Brain
Struck by the weight of damning scientific evidence, the Guinness Book of World
Records  has  stopped  recognizing  attempts  to  break  the  sleep  deprivation  world
record. Recall that Guinness deems it acceptable for a man (Felix Baumgartner) to
ascend 128,000 feet into the outer reaches of our atmosphere in a hot-air balloon
wearing a spacesuit, open the door of his capsule, stand atop a ladder suspended
above the planet, and then free-fall back down to Earth at a top speed of 843 mph
(1,358 kmh), passing through the sound barrier while creating a sonic boom with
just his body. But the risks associated with sleep deprivation are considered to be
far, far higher. Unacceptably high, in fact, based on the evidence.
What is that compelling evidence? In the following two chapters, we will learn
precisely  why  and  how  sleep  loss  inflicts  such  devastating  effects  on  the  brain,
linking it to numerous neurological and psychiatric conditions (e.g., Alzheimer’s
disease,  anxiety,  depression,  bipolar  disorder,  suicide,  stroke,  and  chronic  pain),
and on every physiological system of the body, further contributing to countless
disorders and disease (e.g., cancer, diabetes, heart attacks, infertility, weight gain,
obesity,  and  immune  deficiency).  No  facet  of  the  human  body  is  spared  the
crippling,  noxious  harm  of  sleep  loss.  We  are,  as  you  will  see,  socially,
organizationally,
economically,
physically,
behaviorally,
nutritionally,
linguistically, cognitively, and emotionally dependent upon sleep.
This  chapter  deals  with  the  dire  and  sometimes  deadly  consequences  of
inadequate sleep on the brain. The chapter that follows will recount the diverse—
though equally ruinous and similarly fatal—effects of short sleep on the body.
PAY ATTENTION
There are many ways in which a lack of sufficient sleep will kill you. Some take
time; others are far more immediate. One brain function that buckles under even
the  smallest  dose  of  sleep  deprivation  is  concentration.  The  deadly  societal
consequences of these concentration failures play out most obviously and fatally
in the form of drowsy driving. Every hour, someone dies in a traffic accident in the
US due to a fatigue-related error.

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There  are  two  main  culprits  of  drowsy-driving  accidents.  The  first  is  people
completely  falling  asleep  at  the  wheel.  This  happens  infrequently,  however,  and
usually requires an individual to be acutely sleep-deprived (having gone without
shut-eye  for  twenty-plus  hours).  The  second,  more  common  cause  is  a
momentary lapse in concentration, called a microsleep. These last for just a few
seconds, during which time the eyelid will either partially or fully close. They are
usually  suffered  by  individuals  who  are  chronically  sleep  restricted,  defined  as
getting less than seven hours of sleep a night on a routine basis.
During a microsleep, your brain becomes blind to the outside world for a brief
moment—and not just the visual domain, but in all channels of perception. Most
of  the  time  you  have  no  awareness  of  the  event.  More  problematic  is  that  your
decisive control of motor actions, such as those necessary for operating a steering
wheel or a brake pedal, will momentarily cease. As a result, you don’t need to fall
asleep  for  ten  to  fifteen  seconds  to  die  while  driving.  Two  seconds  will  do  it.  A
two-second microsleep at 30 mph with a modest angle of drift can result in your
vehicle  transitioning  entirely  from  one  lane  to  the  next.  This  includes  into
oncoming traffic. Should this happen at 60 mph, it may be the last microsleep you
ever have.
David  Dinges  at  the  University  of  Pennsylvania,  a  titan  in  the  field  of  sleep
research and personal hero of mine, has done more than any scientist in history
to  answer  the  following  fundamental  question:  What  is  the  recycle  rate  of  a
human  being?  That  is,  how  long  can  a  human  go  without  sleep  before  their
performance  is  objectively  impaired?  How  much  sleep  can  a  human  lose  each
night, and over how many nights, before critical processes of the brain fail? Is that
individual even aware of how impaired they are when sleep-deprived? How many
nights of recovery sleep does it take to restore the stable performance of a human
after sleep loss?
Dinges’s  research  employs  a  disarmingly  simple  attention  test  to  measure
concentration. You must press a button in response to a light that appears on a
button box or computer screen within a set period of time. Your response, and the
reaction  time  of  that  response,  are  both  measured.  Thereafter,  another  light
comes  on,  and  you  do  the  same  thing.  The  lights  appear  in  an  unpredictable
manner,  sometimes  in  quick  succession,  other  times  randomly  separated  by  a
pause lasting several seconds.
Sounds easy, right? Try doing it for ten minutes straight, every day, for fourteen
days. That’s what Dinges and his research team did to a large number of subjects
who  were  monitored  under  strict  laboratory  conditions.  All  of  the  subjects

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started off by getting a full eight-hour sleep opportunity the night before the test,
allowing  them  to  be  assessed  when  fully  rested.  Then,  the  participants  were
divided  into  four  different  experimental  groups.  Rather  like  a  drug  study,  each
group was given a different “dose” of sleep deprivation. One group was kept up for
seventy-two hours straight, going without sleep for three consecutive nights. The
second  group  was  allowed  four  hours  of  sleep  each  night.  The  third  group  was
given six hours of sleep each night. The lucky fourth group was allowed to keep
sleeping eight hours each night.
There  were  three  key  findings.  First,  although  sleep  deprivation  of  all  these
varied  amounts  caused  a  slowing  in  reaction  time,  there  was  something  more
telling:  participants  would,  for  brief  moments,  stop  responding  altogether.
Slowness  was  not  the  most  sensitive  signature  of  sleepiness,  entirely  missed
responses  were.  Dinges  was  capturing  lapses,  otherwise  known  as  microsleeps:
the real-life equivalent of which would be failing to react to a child who runs out in
front of your car when chasing a ball.
When describing the findings, Dinges will often have you think of the repeating
beep  from  a  heart  monitor  in  a  hospital:  beep,  beep,  beep.  Now  picture  the
dramatic  sound  effect  you  hear  in  emergency  room  television  dramas  when  a
patient starts to slip away as doctors frantically try to save their life. At first, the
heartbeats are constant—beep, beep, beep—as are your responses on the visual
attention  task  when  you  are  well  rested:  stable,  regular.  Switch  to  your
performance when sleep-deprived, and it is the aural equivalent of the patient in
the hospital going into cardiac arrest: beep, beep, beep, beeeeeeeeeeeeeep. Your
performance  has  flatlined.  No  conscious  response,  no  motor  response.  A
microsleep. And then the heartbeat comes back, as will your performance—beep,
beep, beep—but only for a short while. Soon, you have another arrest: beep, beep,
beeeeeeeeeeeeeep. More microsleeps.
Comparing the number of lapses, or microsleeps, day after day across the four
different experimental groups gave Dinges a second key finding. Those individuals
who slept eight hours every night maintained a stable, near-perfect performance
across  the  two  weeks.  Those  in  the  three-night  total  sleep  deprivation  group
suffered catastrophic impairment, which was no real surprise. After the first night
of no sleep at all, their lapses in concentration (missed responses) increased by
over 400 percent. The surprise was that these impairments continued to escalate
at the same ballistic rate after a second and third night of total sleep deprivation,
as if they would continue to escalate in severity if more nights of sleep were lost,
showing no signs of flattening out.

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But  it  was  the  two  partial  sleep  deprivation  groups  that  brought  the  most
concerning  message  of  all.  After  four  hours  of  sleep  for  six  nights,  participants’
performance  was  just  as  bad  as  those  who  had  not  slept  for  twenty-four  hours
straight—that is, a 400 percent increase in the number of microsleeps. By day 11
on this diet of four hours of sleep a night, participants’ performance had degraded
even  further,  matching  that  of  someone  who  had  pulled  two  back-to-back  all-
nighters, going without sleep for forty-eight hours.
Most  worrying  from  a  societal  perspective  were  the  individuals  in  the  group
who obtained six hours of sleep a night—something that may sound familiar to
many of you. Ten days of six hours of sleep a night was all it took to become as
impaired  in  performance  as  going  without  sleep  for  twenty-four  hours  straight.
And like the total sleep deprivation group, the accruing performance impairment
in  the  four-hour  and  six-hour  sleep  groups  showed  no  signs  of  leveling  out.  All
signs  suggested  that  if  the  experiment  had  continued,  the  performance
deterioration would continue to build up over weeks or months.
Another  research  study,  this  one  led  by  Dr.  Gregory  Belenky  at  Walter  Reed
Army  Institute  of  Research,  published  almost  identical  results  around  the  same
time. They also tested four groups of participants, but they were given nine hours,
seven hours, five hours, and three hours of sleep across seven days.
YOU DO NOT KNOW HOW SLEEP-DEPRIVED YOU ARE WHEN YOU
ARE SLEEP-DEPRIVED
The  third  key  finding,  common  to  both  of  these  studies,  is  the  one  I  personally
think  is  the  most  harmful  of  all.  When  participants  were  asked  about  their
subjective  sense  of  how  impaired  they  were,  they  consistently  underestimated
their  degree  of  performance  disability.  It  was  a  miserable  predictor  of  how  bad
their performance actually, objectively was. It is the equivalent of someone at a
bar  who  has  had  far  too  many  drinks  picking  up  his  car  keys  and  confidently
telling you, “I’m fine to drive home.”
Similarly problematic is baseline resetting. With chronic sleep restriction over
months  or  years,  an  individual  will  actually  acclimate  to  their  impaired
performance,  lower  alertness,  and  reduced  energy  levels.  That  low-level
exhaustion  becomes  their  accepted  norm,  or  baseline.  Individuals  fail  to
recognize how their perennial state of sleep deficiency has come to compromise
their mental aptitude and physical vitality, including the slow accumulation of ill
health. A link between the former and latter is rarely made in their mind. Based
on  epidemiological  studies  of  average  sleep  time,  millions  of  individuals

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unwittingly  spend  years  of  their  life  in  a  sub-optimal  state  of  psychological  and
physiological functioning, never maximizing their potential of mind or body due
to their blind persistence in sleeping too little. Sixty years of scientific research
prevent me from accepting anyone who tells me that he or she can “get by on just
four or five hours of sleep a night just fine.”
Returning  to  Dinges’s  study  results,  you  may  have  predicted  that  optimal
performance  would  return  to  all  of  the  participants  after  a  good  long  night  of
recovery  sleep,  similar  to  many  people’s  notion  of  “sleeping  it  off”  on  the
weekends to pay off their weeknight sleep debt. However, even after three nights
of  ad  lib  recovery  sleep,  performance  did  not  return  to  that  observed  at  the
original baseline assessment when those same individuals had been getting a full
eight hours of sleep regularly. Nor did any group recover all the sleep hours they
had  lost  in  the  days  prior.  As  we  have  already  learned,  the  brain  is  incapable  of
that.
In a disturbing later study, researchers in Australia took two groups of healthy
adults, one of whom they got drunk to the legal driving limit (.08 percent blood
alcohol),  the  other  of  whom  they  sleep-deprived  for  a  single  night.  Both  groups
performed  the  concentration  test  to  assess  attention  performance,  specifically
the  number  of  lapses.  After  being  awake  for  nineteen  hours,  people  who  were
sleep-deprived were as cognitively impaired as those who were legally drunk. Said
another way, if you wake up at seven a.m. and remain awake throughout the day,
then go out socializing with friends until late that evening, yet drink no alcohol
whatsoever, by the time you are driving home at two a.m. you are as cognitively
impaired in your ability to attend to the road and what is around you as a legally
drunk  driver.  In  fact,  participants  in  the  above  study  started  their  nosedive  in
performance  after  just  fifteen  hours  of  being  awake  (ten  p.m.  in  the  above
scenario).
Car  crashes  rank  among  the  leading  causes  of  death  in  most  first-world
nations. In 2016, the AAA Foundation in Washington, DC, released the results of
an extensive study of over 7,000 drivers in the US, tracked in detail over a two-year
period.
I
The key finding, shown in figure 12, reveals just how catastrophic drowsy
driving is when it comes to car crashes. Operating on less than five hours of sleep,
your risk of a car crash increases threefold. Get behind the wheel of a car when
having slept just four hours or less the night before and you are 11.5 times more
likely  to  be  involved  in  a  car  accident.  Note  how  the  relationship  between
decreasing  hours  of  sleep  and  increasing  mortality  risk  of  an  accident  is  not

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linear,  but  instead  exponentially  mushrooms.  Each  hour  of  sleep  lost  vastly
amplifies that crash likelihood, rather than incrementally nudging it up.