Sleep Deprivation Effects | Part 3

This part of Matthew Walker’s book on sleep is perhaps the most enthralling and simultaneously terrifying.  Sleep deprivation, more than anything else has been linked to heart disease, diabetes, cancer, gene transcription error and more.

My sister doesn’t live on normal-people time, both with night shift work once or twice a month, as well as very irregular sleeping hours.  And this line from the book in particular had me really hoping she would read this book and consider her sleep habits:

“The scientific evidence linking sleep disruption and cancer is now so damning that the World Health Organization has officially classified nighttime shift work as a “probable carcinogen”. (p166)”

Sleep Deprivation And The Brain

  • Research by David Dinges (University of Pennsylvania found in research that those who obtained six hours of sleep a night for ten days became as impaired in performance as going without sleep for twenty-four hours straight (p136)
  • With chronic sleep restriction over months or years, an individual will actually acclimate to their impaired performance, lower alertness and reduced energy levels and won’t be able to recognise their sub optimal existence. (p137)
  • Researchers in Australia found that after being awake for 19 hours, people who were sleep deprived wee as cognitively impaired as those who were legally drunk. (p138)
  • Infact each hour of sleep loss increases the likelihood of a crash.  E.g. At 6-7 hours you’re 1.3 times more likely to have a crash, and at less than 4 hours, you’re 11.5 times more likely to have a crash. After around 16 hours of being awake, the human brain begins to fail. (p139)
  • Sleep loss PLUS alcohol is not additive, it is multiplicable.
  • Vehicle accidents caused by drowsy driving exceeds those caused by alcohol and drugs combined.  Drowsy driving alone is worse than driving drunk.  When you’re drunk you will be LATE in reacting.  When you’re asleep, you stop reacting altogether. (p140)
  • Truck drivers are 200 to 500 percent more likely to be involved in a traffic accident.  And when a truck driver loses his or her life in a drowsy-driving crash, they will, on average, take 4.5 other lives with them. (p141)
  • The most dangerous time of flight in long haul travel is landing, which arrives at the end of a journey, when the greatest amount of sleep deprivation has often accrued. (p143)
  • A rare collection of individuals are able to survive on si hours of sleep and show minimal impairment.  The explanation appears to lie in the sub variant of a gene called BHLHE41 (also known as DEC2).  Expressed as a percentage of the population, the number of people who are like this are zero!  So it is very rare indeed. (p145)
  • Analysis of brain scans revealed the largest effects Matthew Walker has measured in his research to date – on the amygdala – which showed a 60% amplification in emotional reactivity in participants who were sleep-deprived. (p146)
  • Insufficient sleep doesn’t push the brain into a negative mood state and hold it there, instead it swings excessively to both positive and negative extremes. (p148)
  • Studies of adolescents have identified a link between sleep disruption and suicidal thoughts, suicide attempts and suicide completions in the days after. (p148)
  • Insufficient sleep also determines relapse rates in numerous addition disorders, associated with psychoactive substances. (p149)
  • Dr Allison Harvey from the University of California, Berkeley has found that should you improve sleep quality in patients suffering from several psychiatric conditions using cognitive behavioural therapy for insomnia (CBT-I), you can improve symptom severity and remission rates. (p151)
  • In one of Matthew Walker’s own experiments to understand the impact of students pulling “all nighters” – when comparing the effectiveness of learning between the two groups, there was a 40 percent deficit in the ability of the sleep deprived group to cram new facts into the brain relative to the group that obtained a full night of sleep.  That is the difference between acing an exam and failing it miserably. (p154)
  • In another test on 133 undergrads to learn a visual memory task, it was found that a night of sleep strengthened the newly learned memories, boosting their retention.  Additionally, the more nights of sleep participants had before they were ested, the better their memory was. Those who didn’t sleep the first night after learning, had no memory consolidation – i.e. if you don’t sleep the night that you learn, you lose the memories. (p156)
  • Dr Maiken Nedergaard at the University of Rochester found that a kind of sewage network called the glymphatic system exists within the brain.  This system collects and removes contaminants that are generated by the hard work performed by neurons in your brain.  It is at night, during deep NREM sleep that there is a 10-20 fold increase in the power cleansing going on in your brain.  The REASON the cleaning is so effective during this time is that the glial cells shrink in NREM sleep which allows he cerebrospinal fluid to clean out the gunk from that day’s neural activity. (p160)
  • Should you experimentally prevent a mouse from getting NREM sleep, there is an immediate increase in amyloid deposits (associated with Alzheimers) in the brain.  Put another way, wakefulness is low-level brain damage, while sleep is neurological sanitation. (p161)


Sleep Deprivation And The Body

  • A 2011 study tracked more than held a million men and women of varied ages, races, and ethnicities across with different countries.  Progressively shorter sleep was associated with a 45 percent increased risk of developing and/or dying from coronary heart disease within seven to twenty-five years. (p165)
  • A Japanese study of over 4,000 male workers over a 14 year period found that those sleeping 6 hours or less were 400 to 500 percent more likely to suffer one or more cardiac arrests than those sleeping more than six hours. (p165)
  • Part of the reason the heard suffers so dramatically under the weight of sleep deprivation is blood pressure.  Lack of sleep can pump up the pressure in the veins of your entire body. (p165)
  • Daylight savings is a “global experiment” in which 1.5 billion people are forced to reduce their sleep by one hour or less for a single night each year.  In the Northern Hemisphere, the switch to daylight savings time in March results in most people losing an hour.  In tabulation millions of hospital records, we find a frightening spike in heart attacks the following day.  The opposite happens when people gain an hour. (p169)
  • Does diabetes impair your sleep, or does short sleep impair your body’s ability to regulate blood sugar, thereby causing diabetes? In this experiment it was found that formerly healthy participants were 40 percent less effective at absorbing a standard dose of glucose, compared to when they were fully rested. (p171)
  • Do we eat more when sleeping less? In this experiment, the same individuals ate 300 calories more each day (1k calories per week) vs when they were getting a full night’s sleep. (p173).  Note on p175 – we don’t eat more when we are sleep deprived because we burn extra calories to stay awake.
  • A recent discovery has been made that sleep loss increases levels of circulating endocannabinoids, which are chemicals produced by the body that are very similar to the drug cannabis.  Like marijuana use, these chemicals stimulate appetite and increase your desire to snack. (p174)
  • In an experiment comparing patterns of brain activity when participants are shown “good” food vs “bad” food, found tat supervisor regions of the prefrontal cortex required for thoughtful judgements and controlled decisions are silenced in their activity by lack of sleep. The more prial deep-brain structures that drive motivations and desire were instead amplified in response to the food images – so high calorie foods became significantly more desirable to the sleep deprived, by 600 extra calories on average. (p176)
  • Evidence for the effect of sleep loss on obesity has been gathered over the past 30 years, back in 1940 when humans had close to 9 hours sleep a night, obesity was less than 5%, and continues its reverse trajectory through time with now the average sleep being 6.5 hrs and the obesity rate at 35%. (p177)
  • When losing weight, the amount of sleep you get affects the type of weight you lose.  If 6 hours or less, 70% of the weight lost is muscle, when sleeping correctly, 50% of the weight lost is fat, whilst preserving muscle. (p178)
  • Take a group of lean, health young males in their mid-twenties and limit their to five hours sleep for one week.  The hormone blending effect ages the man by 15 years in terms of testosterone virility. (p179)
  • Routinely sleeping less than six hours a night results in a 20 percent drop of follicular-releasing hormone in women. (p179)
  • Women who work erratic hours were 80% more likely to suffer from issues of sub fertility. 33% higher rate of abnormal menstrual cycles too. (p180)
  • Women who do become pregnant and routinely sleep less than eight hours a night are significantly more likely to suffer a miscarriage in their first trimester, relative to those consistently sleeping eight hours or more a night. (p180)
  • The less an individual  sleeps in the week before facing the active common cold viru, the more likely it was they would be infected.  In those sleeping five hours on average, the infection rate was almost 50%, in those sleeping seven or more hours a night in the week prior, the infection rate was just 18%. (p182)
  • A study in 2002 showed that sleep profoundly impacts responses to a standard flue vaccine.  Those participants who obtained seven to nine hours sleep in the week before getting the flu shot generated a powerful antibody reaction.  Those who were sleep restricted produced less than 50 percent of the immune reaction to their well slept counterparts.  Similar results have been reported for hep A and hep B vaccines too. (p183)
  • A brief dose of short sleep can affect your cancer fighting immune cells.  One night of 4 hours of sleep can sweep away 70% of your natural killer cells vs a full eight hour night of sleep. (p184.)
  • Lack of sleep also significantly affects cancer cell progression once taken hold.  Experiments from the University of Chicago (results found when mice were injected with malignant cells and tumor progression tracked over 4 weeks).  Sleep deprived mice suffered a 200 percent increase in the speed and size of cancer growth relative to the well-rested group. (p185)
  • Not getting enough sleep when fighting a battle against cancer is like pouring gasoline or an already aggressive fire. The scientific evidence linking sleep disruption and cancer is now so damning that the World Health Organization has officially classified nighttime shift work as a “probable carcinogen”. (p166)
  • Thousands of genes in the brain depend on sleep for stable regulation.  Deprive a mouse of sleep for a day and the activity of these genes will drop by over 200%.  Like a stubborn file that refuses to be transcribed by a printer, when you don’t lavish these DNA segments with enough sleep, they will not translate their instrutinal code into printed action and give the brain and body what they need. And the effect on humans is as pronounced as it is in mice. (p187)
















Sleep and Memory | Part 2

The second half of Why We Sleep starts like this “Amazing breakthrough!  Scientists have discovered a revolutionary new treatment that makes you live longer.  It enhances your memory and makes you more creative.  It makes you look more attractive.  It keeps you slim and lowers food cravings. It protects you from cancer and dementia.  It wards off colds and the flu.  It lowers your risk of heart attacks and stroke, not to mention diabetes.  You’ll even feel happier, less depressed and less anxious.  Are you interested?”

Hyperbolic as this may seem, nothing about this fictitious advertisement is inaccurate when it comes to sleep.

All the notes I highlight on sleep below are related to scientific studies performed by Matthew Walker and his team, or others in the scientific community.  For ease of writing and reading flow, I won’t note the sources here but I’ll give you the page in the book which elaborates in each case and the book index contains all of the sources.



  • Which sleep confers the greater memory savings benefit? (deep NREM or REM)?  An early night, right in deep NREM. (p113)
  • Experimental results of Jenkin and Dallenbach have now been replicated time and time again with a memory retention benefit of between 20 and 40 percent being offered by sleep, compared to the same amount of time awake. (p113)
  • The more sleep spindles an individual obtains during a nap, the greater the restoration of their learning when they wake up (p110)
  • In 2006 a team in Germany ran a study to insert small amounts of electrical voltage during deep sleep.  When done pulsing in rhythmic time with the brain’s own waves, both the size of the brain waves and the number of sleep spindles were increased by the stimulation and provided a memory enhancement of 40% over the control group. (don’t try this at home!) (p117)
  • A swiss team suspended a bed frame on ropes and rocked the bed from side to side at controlled speeds.  Slow rocking increased the depth of deep sleep and boosted the quality of slow brain waves and more than doubled the number of sleep spindles.  (p118)
  • Using MRI scans, scientists have since looked deep into the brains of participants to see where those memories are being retrieved from before sleep relative to after sleep.  Information packets are recalled from completely different locations. Before sleep, participants fetch newly learned information from the hippocampus.  After sleep, from the neocortex. (p114)
  • Sleep stimulation efforts to date are indiscriminate – that is, you can’t really choose what to remember or what to forget. Science now has a new method called “targeted memory re-activation”.  Before going to sleep in this test, participants were shown not just images at different locations and this would be accompanied with a sound (e.g. a meow for an image of a cat).  When asleep, participants were played back the sounds on low volume with speakers at either side of their bed.  The memories recalled the next day were biased significantly toward those reactivated during sleep using the sound cues. This is the type of thing you could use for some SERIOUS brainwashing. (p119).
  • In another experiment, when participants were given words to remember as well as an indicator as to whether to remember or forget the word, after sleep (vs the non sleep group), memory was selectively boosted for those that had been tagged to be remembered.
  • Which stage of sleep determines what memories should be priorities vs removed? NREM sleep – and the very quickest of sleep spindles.  Eternal Sunshine Of the Spotless Mind here we come! (p122)



  • The term “muscle memory” is a misnomer.  Muscles themselves have no suc memory: a muscle that is not connected to a brain cannot perform any skilled actions, now does a muscle store skilled routines.  Muscle memory is, in fact, brain memory. Training and strengthening muscle can help you better execute a skilled memory routine, but the memory routine, the memory program – resides exclusively in the brain. (p123)
  • In an experiment teaching right handed people to type a number sequence with their left hand, those who slept showed a 20% jump in performance speed  and a 35% improvement in accuracy vs those who were tested before bed.  Those then tested before bed were re-tested in the morning and got the same bump in performance.  So the brain keeps improving skill memories without practice. (p125)
  • When the brain transfers skill memories, its not look fact / info based memory, the motor memories are shifted to brain circuits that operate below the level of consciousness.  (p127)
  • The type of sleep responsible for overnight motor skills enhancement is directly related to the amount of stage 2 NREM, especially in the last two hours of an eight hour night of sleep. (p127)


  • The less sleep an athlete has, the higher the the likelihood of injury.  At 6 hours average, the change of injury is 72%. What!!  Compared to just 18% at 9 hours average sleep or 35% at 8 hours average sleep. (p129)
  • One example of this is the difference in an NBA player’s stats when measuring performance on games played on nights after 8 hours or more vs those with less than 8 hours (p130):
    • 8 hours or more:
      • +12% increase in minutes played
      • +29% increase in points/minute
      • +2% increase in three-point percentages
      • +9% increase i free-throw percentage
    • Less than 8 hours:
      • +37% increase in turnovrs
      • +45% increase in fouls committed
  • At the most dramatic time of motor learning in any human’s life (when we learn to stand and walk as an infant), there is a consistent spike in stage 2 NREM sleep, incring sleep spindles, right around the time of transition from crawling to walking. (p131)


I’m splitting these posts into more parts so you can read it sooner – as at my current rate it might take me a couple of weeks to get through all the notes.  The next post will be on the impacts of sleep deprivation and health outcomes and then we’ll move on to the awesome world of dreams!

Sleep: Part 1 – How Sleep Works

For a very long time I have hated sleep.  It was rude, inconvenient and most importantly, I didn’t understand its purpose.  I always thought to myself “What if there was some secret way that I could always be awake and learning”. In fact, it was the lack of time I had available to learn (mostly due to the fact that I run a business), that I felt frustrated in sleep for getting in my way.

Having some time on my hands over the holidays, I bought a book called “Why We Sleep”, written by neuroscientist Matthew Walker who has been researching sleep for 20 years and published over 100 papers on the topic.  It’s the first book of its kind…ever, really.  Before this book there were books like “Sleep” by Nick Littlehales and “Sleep Smarter” and “Sleep Better”.  But they were all really focussed on techniques for sleeping better, not understanding the why, as well as the consequences of not sleeping. From what I can tell, this is the very first to bring together all the science and answers into one spot.

I devoured this book in 2 days and thought I’d summarise all the most salient bits for anyone who is interested in the science and reason behind why we sleep and why it is so important (especially my little sister who’s sleeping patterns are erratic due to her work).

This new information has immediately changed my behaviour which I will showcase below:

This was how I slept last night…


Fitbit image of my sleep over an 8 hour period.  See how the time in REM increases in those final two hours.  Had I slept 6 hours, I would not have received any of that REM stage sleep – which we’ll discuss why that is SO important later on in this post.

According to my Fitbit, the amount of sleep in each stage was perfect for the benchmark.


Image of my night’s sleep in comparison to benchmarks.  Noice.

Prior to that however, I had been completely neglecting my REM sleep.  This was what my sleep looked like in late Oct, early Nov this year.


Image of my sleep before this book…eeeep!

Matthew Walker hits the nail on the head with this passage from Page 5 of “Why We Sleep”:

Society’s apathy toward sleep has, in part, been caused by the historic failure of science to explain why we need it…To better frame this state of prior scientific ignorance, imagine the birth of your first child. At the hospital, the doctor enters the room after preliminary tests and says “Congratulations, its a healthy baby boy. We’ve completed all of the preliminary tests and everything looks good”. She smiles reassuringly and starts walking toward the door. However, before exiting the room she turns around and says, “There is just one thing. From this moment forth, and for the rest of you child’s entire life, he will repeatedly and routinely lapse into a state of apparent coma. It might even be filled with stunning and bizarre hallucinations. This state will consume one-third of his life and I have absolutely no idea why he’ll do it, or what it is for. Good luck!”


  • We all have a biological clock called the suprachiasmatic nucleus
  • This clock, which is called our “circadian rhythm”, is approximately one day…but not exactly.  Mostly it’s a little more than a day – around 26 hours. (p17)
  • What the suprachiasmatic nucleus does is it sits in the middle of your brain just above the crossing point of the optic nerves coming from your eye balls which  meet at the middle of your brain and then switch sides.  Why? So it can “sample” the light signal being sent from each eye along the optic nerve and use it as reliable light information to reset the inherent time inaccuracy we have. DAMN, What??! (p18)
  • Our core body temperature goes up and down in line with this rhythm every day. (p19)
  • Whether you are a “morning” or a “night” person (your chronotype), depends on your genes (as discovered by these guys over the course of 20 years of research).  This means we cannot control our desire to be an early riser or a late sleeper – but unfortunately work, school and other schedules don’t care about this. (p21)
  • Melatonin is a hormone released from the pineal gland in the brain that is kind of like the voice of the timing official in a running race that pulls the start trigger.  It gets released every evening, on average it picks up pace after 6pm and reaches its peak at 1am. (p22-24)
  • For every day you are in a different timezone (this includes daylight savings), your suprachiasmatic nucleus can only adjust by 1 hour.  So if you’re in a timezone 15 hours behind your own, you’ll take about 15 days to fully readjust.  Or if going between night and day shifts, that means even just 2 shifts per month will mean your body is in a constant state of playing catch up. (p25)
  • Scientists have found the strain of constant jetlag physically shrinks the learning areas of the brain and short term memory is significantly impaired, along with far higher rates of cancer and type 2 diabetes compared to the rest of the population or even carefully controlled match individuals who don’t travel as much (p26)


  • The other factor that determines when we wake or sleep is a chemical called adenosine which continues to increase with each moment we’re awake and that increases your desire to sleep. (p27)
  • You can artificially mute this sleep signal with stimulants (the most widely used of which is caffeine but can also include chocolate and types of teas). Stimulants latch on to the adenosine receptors in the brain and stops adenosine from communicating to your brain that you are, in fact, sleepy!   With a half life of 5-7 hours to get out of your system, many bad nights of sleep can come from the cup of coffee you had at 6pm. (p30)


Enough said about why caffeine is so bad for you…just because society has completely normalised it doesn’t make it good.

  • In theory the longer you’re awake the sleepier you should feel BUT your circadian rhythm and the sleep pressure are two connected processes but not reliant on one another.  This is why when you have an all nighter, you may feel very tired around 5-6am but get a 2nd burst of energy in the morning when your underlying circadian rhythm is telling you it’s day time again! (p34)

IMG_9696 2.JPG


  • There are two categories of sleep:
    • NREM (Non rapid eye movement sleep – broken into x2 stages of light sleep and x2 stages of deep sleep)
    • REM (rapid eye movement sleep).  This is when you dream.
  • The sleep cycle doesn’t repeat itself exactly.  During the 2nd half of the night (or the 2nd 4 hours of an 8 hour sleep), you’ll see more REM sleep occuring on each cycle and you get slightly more REM on each cycle.  When you cut your sleep short, that’s the bit that you’re most likely to be missing out on. (p42-43)
  • If you were to convert the NREM sleep into a sound, you’d hear a quick sound trill every now and then, lasting a few seconds – like a fast purr of a cat.  These are called “sleep spindles” and one of their jobs is to protect your sleep by shielding you from external noises. (p49)
  • The deepest and slowest brainwaves of NREM sleep are pretty damn amazing – it’s a complete display of neural collaboration.  When you’re awake, your brain is like an FM radio station – everything in its spot, communicating in its own section of your brain, but it can’t communicate past that point.  When you enter this stage of sleep your brain starts to “sing” together and those waves lengthen out like an AM radio station.  They do this so they can communicate their data across longer distances, to process your short term memory across to your long term memory.  Like a data back up of sorts! (p50 and 51)
  • Waking brain activity is mostly concerned with data reception, while NREM is a state of reflection that helps to transfer and distill the memories of the day and REM integrates it all that new info together with all your past experiences to help you build a more accurate model of how the world works (p52 and 53)
  • When you are in REM sleep, you are completely paralysed.  Have you ever tried to wake yourself out of a bad dream in the midst of screaming and then as you come into wakefulness you think you’re shouting but your mouth is shut and you can’t move, and then you let out a small whimper once you’re able?  Then you’ve experienced a slip in the cross over of that state of paralysis.  You truly were unable to move… (p54)
  • Why did evolution do this?  So that we didn’t go crazy and act out our dreams of course!  Makes a lot of sense. (p54)


  • If  your brain is given the option between NREM or REM sleep after being deprived of sleep, it will feast on the NREM sleep first on the recovery night, but then it will switch to more REM on the following nights – so I guess it must be “batch downloading” and then “batch processing” which makes sense. (p63)


  • Dolphins dream with half their brain at a time.  One half needs to stay awake to maintain life necessary movement in the aquatic environment. (p64)
  • Birds can do the same! (p65)


  • Biologically we have a biphasic sleep pattern, that means we are built to have one long sleep, as well as a nap somewhere between 12pm and 3pm in the afternoon. (p69)
  • This means all that time I thought I was feeling tired after lunch, the real reason is that my biological clock was TELLING me I am tired…regardless of whether lunch has been eaten or not.
  • When Greece changed to remove the afternoon nap that had been the cultural norm, scientists studied the outcome by comparing those who removed the nap to those who did not across 23,000 Greek adults across 6 years. Those who abandoned the nap went on to suffer a 37% increase risk of death from heart disease – especially working men where the risk of non napping increased to over 60%.  WHAT?? This is insane. (p71)


  • The amount of sleep we humans get in comparison to other primates is quite a lot less – 8 vs 15, BUT we have a disproportionate amount of REM sleep, between 20-25% vs 9%. (p72)
  • REM sleep allows us to regulate our emotions.  It basically builds our EQ.  If you scale this across millennia, you can start to see how this REM sleep pattern contributed to the rich socio-emotional basis of modern society (p75)
  • The second thing that REM sleep contributes to is creativity. NREM sleep helps transfer and make safe newly learned information into long-term storage sites of the brain.  But it is REM sleep that takes these freshly minted  memories and begins colliding them with the entire back catalogue of your life’s autobiography.  These mnemonic collisions during REM sleep spark new creative insights as novel links are forged between unrelated pieces of information.  Sleep cycle by sleep cycle, REM sleep helps construct vast associative networks of information in the brain.  REM sleep can even take a step back and divine overarching insights and gist – that is, what all knowledge gathered means as a whole vs collection of separate pieces of information. (p75)


  • Babies spend most of their time, in utero, inside REM sleep. Babies kicking around in there aren’t in response to their parents playing music or speaking but are more likely random burst of brain activity that are typical of REM sleep (sorry first time Mums!).  The difference with babies is at this point the brain hasn’t developed enough to paralyse them while they’re in this sleep state as it would when they come into the real world, so off they go, bopping around like its a dance party in there! (p78)
  • Ignoring severe alcoholism during pregnancy, even mothers who might have a quick glass of wine or two have a significant impact on the REM sleep of the fetus. After just a glass or two, the unborn infant’s breathing rate drops from 381 per hour to 4 per hour.  Holy crap! Later on the book Matthew Walker refers to research around just human consumption of alcohol and what it does to sleep and the ability to learn…so just imagine what this could be taking from a new human attempting to form its entire physiology?  (p84)
  • About half of all lactating women in western countries consume alcohol in the months during breastfeeding.  But sleep data brings this into question. Newborns normally transition straight into REM sleep after feeding and in several studies where infants have been fed alcohol laced milk, their sleep is more fragmented, they spend more time awake and suffer from a 20-30% suppression of REM sleep.  They’ll often try to get it back once it has been cleared from their bloodstream but it’s not easy for their fledgling systems to do so.  What’s scary is we really don’t know what the long term effects of REM sleep disruption in babies really is at this point (p84-p85)


  • The older a child gets, the longer and more stable their sleep becomes.  This is because their suprachiasmatic nucleus (their biological time clock) doesn’t finish developing until 3-4 months.  Remember how it was noted that the nucleus “samples” light from the optic nerve?  Well as many people know, babies eyes haven’t fully developed at birth – I imagine this impacts on the nucleus’ ability to even sample light accurately… (p86)
  • At 6 months, there is a 50/50 time share across a 14 hr sleep period between NREM and REM sleep while at 5 years, there is a 70/30 split between the two (p87)


  • A second round of brain wiring re architecture happens at the start of adolescence.  Its goal is efficiency and effectiveness.  This stuff completely blew. my. mind. I’m going to just pop in the analogy direct from the book because it explains the process really well:
  • “When an internet service provider first sets up a network, each home in the newly built neighbourhood was given an equal amount of connectivity bandwidth and thus potential for use.  However, that’s an inefficient solution for the long term, since some of these homes will become heavy bandwidth users over time, while other homes will consume very little.  Some homes may even remain vacant and never use any.  To reliably estimate what pattern of demand exists, the Internet service provider needs time to gather usage statistics.  Only after a period of experience can the provider make an informed decision on how to retune the original network structure it put in place, dialing back connectivity to low-use homes, while increasing connectivity to other homes with high bandwidth demand.  It is not a complete redo of the network, and much of the original structure will remain in place.  After all, the Internet service provider has done this many times before and they have a reasonable estimate of how to build a first pass of a network.  But a use-dependent reshaping and downsizing must still occur if maximum network efficiency is to be achieved.” (p88)
  • The change in NREM sleep always precedes the cognitive and developmental milestones within the brain by several weeks or months, implying a direction of influence: i.e. deep sleep may be the driving force of brain maturation, not the other way around. (p90)
  • When scientists deprived juvenile rates of deep sleep, they halted the maturational refinement of brain connectivity, demonstrating a causal role for deep NREM sleep in propelling the brain to healthy adulthood. (p91)
  • A separate series of studies observed that in young individuals at high risk of developing schizophrenia, there is a two- to threefold reduction in deep NREM sleep.  Furthermore, the electrical brainwaves of NREM sleep are not normal in their shape or number. Faulty pruning of brain connections is now one of the most active areas of investigation in psychiatric illness. (p92)
  • Adolescent teenagers have a different cercadian rhythm to both their parents and their young siblings. A 9 yo rhythm would sleep at 9pm, while a 16 yo would still be at peak wakefulness perhaps even to 11am or 12pm.  Asking a teenager to go to bed at 10pm is the circadian equivalent of asking a parent to fall asleep at 7pm. (p93)


  • Broadly speaking, older people need just as much sleep as we do – however their machinery for creating powerful sleep pressure and circadian rhythm change in such a way that it makes it more difficult to get the sleep they need.  i.e. it is a myth that “older people need less sleep”. (p95-99)
  • Matthew suggests two modifications for seniors lifestyles who are exercising to help sleep onset – when exercising in the morning, wear sunglasses to reduce the effect of sunlight on your suprachiasmatic clock that would otherwise keep you on an early-to-rise schedule.  Plus, go back outside in the late afternoon for sunlight exposure but this time don’t wear sunglasses, this will help delay the evening release of melatonin and push the timing of sleep to a later hour. (p100)

In Part 2 of this post I’ll cover off why you should sleep – backed by a bunch of scientific data referenced in the book.

How to tell if that new research study your friend posted on Facebook should be shared…or deleted.

Last week CNN posted an article with the title “Drinking non-cow milk linked to shorter kids, study suggests“.

Let me start by saying, that this statement is in fact correct…but not for all intents and purposes.  What does that mean?  Let’s start at the beginning.

In the media model, article views equals the ability to sell more advertising space which equals revenue for shareholders.  In the science model, replication of a well designed study by other well designed studies and producing the same result (a process that can take years, sometimes decades!) equals an answer that may then be worthy of writing an article about. These organisational models are living in parallel universes where time between them runs at different speeds.  And this is a shame for the consumer.

Imagine a world where as a consumer, you had access to an instant meter of how valid the results of any research study was according to some universally accepted scoring criteria so you weren’t at risk of consuming erm…trash.

Before you read another click-baiting, crowd-pleasing, over-shared, under-researched article, I’m going to jot down a few things for you to take note of, or to take a few extra minutes to research after you read any article reporting on a new scientific finding.  I challenge you NOT to either share the research nor commit the findings to memory until you’ve availed yourself of the facts surrounding the research design.

The most important question to ask is: Did the research study control for confounding variables?

A confounding variable happens when a researcher can’t tell the difference between the effects of different factors on a variable.  There are so many different things that can have an impact on the results of the study and so understanding what “data noise” to remove is critical to making sure that pattern in the data that a researcher might see is unlikely to be due to chance alone.

When reviewing the validity of research results, these are some of the red flags when it comes to research design:

    • Self reported behaviour surveys
      Humans can barely remember what they did on the weekend let alone on a daily or weekly basis five years ago!  That’s not to say that these studies aren’t relevant, simply that the evidence from them would not be considered as strong as say a study where the experimental design had people follow a pattern of behaviour (for the control and placebo groups) across a specific period of time and followed up with them regularly for self reporting across that time period.
    • The lack of a control group, test group (and in some cases) a placebo group
      A control group is a group of participants to whom the treatment isn’t applied, in the test group the variable that the researcher wants to test is introduced and in the placebo group, the participants think they are part of the test group, but they are receiving some sort of alternative to the treatment that will not yield the expected result.  The human brain and body are pretty powerful…when we think we’re getting we can actually experience improvements that don’t really exist!

      However, a placebo group is not always feasible depending on what is being tested so a bit of common sense needs to be applied here. For instance, if you were trying to test some sort of effect related to drinking water, you could have a control group who didn’t drink water, but given everyone knows what water tastes like, attempting to create a “water placebo” would be pretty tough. But a control and test group should be the bare minimum!  And in cases of medication where a placebo can be easily applied, there should ALWAYS be a placebo group.

    • Non randomised
      If the research is experimental in nature (and not survey based), and the report doesn’t say it’s randomised, then it probably isn’t.  A randomised experiment means that participants in the experiment (those put into either control, test or placebo groups) were randomly assigned assigned to them.  i.e. that the researchers weren’t in control of choosing who would be assigned to which group.  If they are, they can introduce all sorts of unconscious bias that could affect the results.
    • Non Blinded or Non Double Blinded
      A blinded study is where the participant in the research is unaware which group (i.e. test, control or placebo) they have been assigned to.  A double blind study is where neither the participant in the research, nor the researcher themselves, knows which group the participants have been assigned to.  That means the researcher might only see a number in place of an individual’s name and details when seeing the results. And the experiment may be designed in such a way that those responsible for data collection, and perhaps physically collecting data from the participants, do not communicate with the researcher (or may not even be known to them).
    • Small sample sizes
      A “sample” is basically a little portion of the broader “population”.  A population in research doesn’t have to mean the population of a country, it may just be the population within a particular category pertinent to the research.  For example “people with Diabetes”, or “people who have been treated for depression”, or “women who have given birth to at least one child”.  The sample size has, because there are random effects that can occur in small samples that even themselves out when you test the same thing on a larger sample size.

      Most good research might start with a smaller sample size to test an initial hypothesis (theory).  They’ll release initial results but caution that due to small sample sizes, more research should be done to see if the results can be replicated on a broader scale so that it can be .  If this is the first research in a particular area to come out and it’s got a small sample size you MUST treat it with caution. It means that it is essentially “baby research” it’s not fully formed yet nor capable of making truly informed conclusions about its own existence!


  • Non peer reviewed – i.e published in a dodgy journal 
    Yep, not all journals are created equal.  A good piece of research should be published by a journal that has a process whereby other scientific peers review the research methodology before accepting it for publishing.  Sometimes good journals will create a single-blind process for doing this – meaning that those reviewing the research don’t know who the author is.  That’s important – because humans have an innate bias to trust people who are perceived to be more credible, despite there potentially being a lack of evidence to support that trust.

    If it has been archived or cited here: that’s a good start.  Apparently this tool helps you figure out how many times the article has been cited in journals (although I’ve not used it before) and this one helps you figure out the ranking of the journal:

    Monash Uni have a bunch of good links and info about assessing journal quality here including:

  • Statistical significance without IMPORTANCE
    Statistical significance is generally agreed that there is either a 5% or lower (sometimes 1% for more rigorous research) probability that the results obtained were due to chance versus the variable being tested.

    That’s a great first step for sure, but significance does not mean importance. Once the study has met the above criteria, ask yourself one, final and very important question “Is this question the right question to be asking, and is the assumption that underpins the question being asked a correct assumption?”


In the next article I’ll use this cnn article to test drive some of the knowledge above.

The Politics of Hormones

For the last two days every human being and animal I’ve crossed paths with has pissed me off.  And I can’t control it.  It was only when my partner gingerly pointed out one day that I seem to want to kill myself (or everyone else) on the same 3 days every month, that I realised that it was overwhelmingly brought on by my monthly hormone cycle.

Double-flowered carnationsThis morning I attempted to make myself feel better by having a healthy breakfast, buying some carnations and painting each fingernail a different colour of the rainbow.  It turns out chucking a hissy fit and have a rage-fueled cleaning spree did the trick instead.  As I was attempting to stuff these beautiful carnations into a ridiculously narrow vase, one of the flower heads popped off and I quickly realised this vase just wasn’t going to work and tension began to build.  I pulled the stems out and briefly glanced around the room only to be struck by the vision capabilities of a vampire, zeroing in on thousands of grotty specs of dust.  The kitchen was a pigsty.  The tension burst.  I screamed and threw the flowers stems across the room like a two year old.  Thankfully no one else was there to witness it.

And there you have it – human hormones in action.  Have too little of one and you become depressed, too much of another and you’re angry.  These regulatory substances that our own bodies produce, sometimes in cycles, sometimes in response to medications or environment, are created and then transported by our blood to stimulate specific cells or tissues into action.  Basically, they’re little chemical messengers that help to keep everything in balance.  Testosterone, Estrogen, Insulin, Oxytocin and even Dopamine as a peripheral hormone – over 50 of them in total.

But as anyone who has attempted to live a balanced life knows…balance is not exactly simple, it’s a constant juggling act.  So here’s my poor female  body, prepping itself to make babies every month while the rest of me has to catch up and balance all its internal chemicals just right to keep me sane.  I’m lucky it can at least do that.

Many of us would like to think we have absolute final control over our actions and disposition, but our predisposition toward certain behaviours or traits are governed by these chemical compounds which are originally a product of genetics or epigenetics, but then subject to change based on our own epigenome and our environment.  For instance, what we choose to eat or not to eat (given foods are also chemicals), will also effect the chemical composition of our guts and our bodies.  Here’s some examples of the power of hormones:

  • Pre-op Female Transexuals take more Estrogen to stimulate breast formation, heightening of voice and change of fat distribution across the body although this cannot change the effects of the androgens (testosterone and others) on the shape of the skeleton. Visa versa for Pre-op Male Transexuals.
  • Men who take more anabolic steroids like testosterone to make bones stronger and muscles bigger can have the side effect of high blood pressure, sharp aggressive moods, increase in body heat and reduced sperm count.Chemical structure of oxytocin.
  • Oxytocin has different effects in men verses women.  In men it improves the ability to identify competitive relationships whereas in women it facilitates the ability to identify kinship.  It is released by the body in high doses during pregnancy and around childbirth in order to ensure proper boding between the mother and the child and it is also released during sex, which is why women tend to interpret sex as having more meaning than males do, because while it can also be released in men – the presence of testosterone interferes with its release.
Cover of "Emotional Awareness: Overcoming...

Cover via Amazon

I have been reading Emotional Awareness which is a book that covers a 3 week conversation between the Dalai Lama and scientist Paul Eckman (who is behind vast tomes of research on human emotion and, in particular, how it is expressed in minute facial expressions.  His work formed the basis of the TV show “Lie to Me”). In the book they talk about the difference between moods and emotions – where a mood is generally not tied to a specific event or circumstance but has a continuous emotional effect, whereas an emotional episode is much more able to be linked to a trigger event.  In some ways, moods trigger emotional episodes that reflect the mood itself, while emotional episodes are often in response to some sort of external trigger.

When I look at this in the context of hormones, I can see how hormones would often be the precipitants of moods, which would then trigger a variety of emotional responses.  The stronger the hormone and stronger the mood, the stronger the emotional response, and of course like all learned human behaviour, these patterns would continue to strengthen over time if performed again and again and can be how people slip into ongoing depression or aggression.

All this also got me thinking about how religion deals with hormones and their effect on humans.  Two particular instances I can think of relate specifically to women:

  1. In Sharia (Islamic) law, two women must bear witness to a crime in order to be heard in court.  This is stated to be due to the emotional nature of women, although on further research I found the story was related directly to Mohammad wanting to save one of his wives from being stoned to death by being caught all one with another man by a woman.  It seemed he often made up rules to suit his worldly purposes.
  2. In Jewish law, a man cannot touch a woman who is in the bleeding section of her monthly cycle.

Interestingly, there seems to be no similar law governing the display of aggression in men which is similarly a hormone fueled disposition.  Perhaps from an evolutionary perspective this is because the male aggression hormone was highly useful during times of empire expansion and the need to protect land, while the female hormal response in its monthly cycle had no broader benefit (from the patriarchs perspective).

Because for the majority of history, both East and West have lived in patriarchal societies, the best way to look at hormones being a determinant of military and political outcomes is through a male sex hormone like Testosterone.  As an example, research in 1992 showed there was no difference in Testosterone levels between black and white boys during adolescence, but in adulthood, black male testosterone levels were much higher which then directly links to other statistics we see on the number of incarcerations of black verses white males.  Of course there are so many other factors involved including race related discrimination and levels of education…etc but hormones remain a factor.  For instance in contrast, there was significant racism in Western countries toward those of Chinese descent and yet their incarceration rate remains lower.  So if we widen out that thinking from groups to countries, we see the possibilities for testosterone levels in any particular age generation to change and potentially fuel the ability for one clan (or country) to change military outcomes, or to resort to military resolutions over negotiation.  Environmental factors also come into play with research showing in adult male rats that experience short term starvation can significantly reduce testosterone levels.

So here we have a mix of chemicals in our bodies which have the potential to guide us to achieve great good or great destruction and yet we have only scratched the surface in controlling their effects through various hormone replacement therapies that often have many unwanted side-effects of their own.

Fitbit: Wireless Personal Trainer

Fitbit: Wireless Personal Trainer (Photo credit:

Interestingly I recently did an interview with Jonathan Teo as part of a Fireside chat run by our meetup group Lean Startup Melbourne.  He led initial investor rounds into Twitter and Instagram and more recently Snapchat and is one of the key people in the tech industry who has been able to predict new technology trends.  One of the key trends being talked about in the tech industry at the moment is wearable tech (being able to monitor body functions insitu) – which is in part being quickly moved forward and expanded by breakthroughs in nanotechnology and size/power of computer chips.

At our last meetup, one of the speakers was from Lab on a Chip in Melbourne who talked about the real possibility in the near future of capabilities being produced that would enable the immediate mapping of genomes and epigenetic markers and then the smart releasing of medications or hormones through a patch (just like a smoking patch…but way smarter!).
Here’s hoping there’s a nanotech-hormone-patch for PMS before I smash a plate….or five.