Sleep: we all do it, and yet somehow it's hard (as most of us can attest every morning). It's also really relevant: as thinkers, creators, and problem solvers, anything that makes our brains less effective matters. Missed sleep makes a difference -- even two fewer hours a night quickly produce measurable cognitive impairment. Things get more interesting when we look at why it's so hard: our sleep cycles are determined by our internal clocks, which often put us in conflict with society's timetables, leaving many of us in a state of "social jet lag", as if we'd been traveling a timezone or more every day. That's not how any of us want to code (or live), I think, and by understanding how and why so many of us are constantly tired, we can start to make things better.
11. Sleep Needs
• Most people need between 7 & 8.5 hr
sleep [4, 6]
• What happens when you get less?
• Is it similar to sleep deprivation?
12. def chronic sleep
restriction
• Getting reduced sleep over repeated nights
• Like an estimated 20%+ of Americans [10]
• How many of us sleep too little?
14. Less sleep, less brain
• Sleep restriction reduces brain function
• Surprise!
• Cumulative effects over time
• Proportional to how much sleep you
skip
15. Responsiveness Test
0 hours sleep:
errors rise quickly
y axis: failures to
respond to test
prompt in time
1 tick = 2 days
Source: [1]
16. Responsiveness Test
8 hours/night:
effectively
normal
1 tick = 2 days
Source: [1]
17. Responsiveness Test
4 hours a night:
in just one week,
you’re in
sleep-deprived
territory
1 tick = 2 days
Source: [1]
18. Responsiveness Test
6 hours a night:
in the second week,
you’re sunk
1 tick = 2 days
Source: [1]
19. Just to be clear
Your brain will hit
sleep-deprived
territory.
This is bad.
1 tick = 2 days
Source: [1]
21. Caveats
• Sleep needs vary between individuals
• What you’ll see are average numbers
• But most of us are average sleepers!
• Studies vary, but only so much
22. Take the weekend off
• OK, but can’t you just sleep it off over
the weekend?
23. Apparently not
• The brain physiologically adapts to less
sleep [2, 4, 9]
• These last for at least several days
• Recovery sleep is physically different
[4]
29. Alternately put
Over 50% of the population wakes btw 8 and 11 AM
Only ~33% naturally wake up before 8 AM
Source: [6] p. 13
30. Yet
• Much of society starts up between 8 and 9
• What happens to all of us whose bodies want to
wake later?
31. Social Jet Lag
• When society time != body time
• Expressed through sleep deprivation
• Like traveling by plane every day
• Over 40% of Central Europeans off by 2+ hours
Source: [6] p. 149
32. Objection
• But, but, surely people can adjust as needed?
• Are we all just lazy bums?
35. Internal Clocks
• All humans (organisms) have internal clocks
• Few run exactly 24 hours per cycle
• On average slightly longer [11]
• Our bodies use light to sync with the world
Source: [6] p. 1, 118-127
38. Entrainment
• Our bodies use light to adjust the internal day
• Light in inner morning shortens the day
• Light in inner evening lengthens it
• The body mixes both to get the right adjustment
Source: [6] p.117-128
39. Problem
• Your day is too long
• You have to emphasize compression
• More morning than evening
• How?
41. And
• If most people have a longer clock, we'd
expect most people to wake later
• And that's what we saw earlier!
42. Implication
• Sleep cycles are determined by biology
• We can't control / change this
• Have to accept people are as they are
43. More proof
Waking times among a homogeneous population
in 1 time zone are controlled by the sunrise
Source: [6] p.158
44. Part III
Sundry
A whirlwind tour of other topics
45. Stuff I don’t have time
to cover*
• Caffeine
• Napping
• Polyphasic sleep / split sleep
• Urban environments / the Great Outdoors
• Core sleep
• Organizing your day to your daily rhythms
• Drinking water to stay awake
* or haven’t yet researched :D
46. Not to speak of...
• Lots of other stuff affect both sleep quality and thinking
• Alcohol, other drugs
• Exercise
• Stress
• Diet
• Working environment
54. Science is fun
• “Some evidence suggests...”
• Hard conclusions are hard
• Explanations, like this, can be preliminary
• Moar studies!
• But the basics presented here are solid
55. A possible mechanism
• Effects of sleep restriction and deprivation
postulated to share a common trigger [1]
• Cumulative excess hours awake
• How much longer you’re up in a given period than you should have
been
• Deprivation effects likely =~ restriction
effects (in proportion)
• Not the only proposed theory
Source: [1]
56. PVT
• Psychomotor vigilance test
• Subjects respond to a visual stimulus
• Measures attention and response time
• Also lapses (response > 500ms)
Source: [12]
57. Do these results matter?
• PVT (the test) measures both reaction time
and sustained attention
• Does it apply to general brain function?
• What’s it gotta do with coding?
59. Sources
1. Van Dongen, H. P. a, Maislin, G., Mullington, J. M., & Dinges, D. F. (2003). The cumulative cost of additional wakefulness:
dose-response effects on neurobehavioral functions and sleep physiology from chronic sleep restriction and total sleep
deprivation. Sleep, 26(2), 117-26. Retrieved from Source: Van Dongen, etc., UPenn Study, 2003 [1]
2. Belenky, G., Wesensten, N. J., Thorne, D. R., Thomas, M. L., Sing, H. C., Redmond, D. P., Russo, M. B., et al. (2003).
Patterns of performance degradation and restoration during sleep restriction and subsequent recovery: a sleep dose-
response study. Journal of Sleep Research, 12(1), 1-12. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/12603781
3. Belenky, G. (1997). Sleep , Sleep Deprivation , and Human Performance in Continuous Operations, 1-13. Retrieved from
http://isme.tamu.edu/JSCOPE97/Belenky97/Belenky97.htm
4. Alhola, P., & Polo-Kantola, P. (2007). Sleep deprivation: Impact on cognitive performance. Neuropsychiatric Disease and
Treatment, 3(5), 553-567. Dove Medical Press. Retrieved from http://www.pubmedcentral.nih.gov/articlerender.fcgi?
artid=2849789&tool=pmcentrez&rendertype=abstract
5. Robinson, E. (2005). Why Crunch Mode Doesn’t Work: 6 Lessons. IGDA Retrieved Feb, 1-6. Retrieved from http://
www.igda.org/why-crunch-modes-doesnt-work-six-lessons
6. Roenneberg, Till. Internal Time: Chronotypes, Social Jet Lag, and Why You're so Tired. Cambridge, MA: Harvard UP, 2012.
Print.
7. Popova, M. (2012). Internal Time : The Science of Chronotypes , Social Jet Lag , and Why You’re So Tired. Retrieved from
http://www.brainpickings.org/index.php/2012/05/11/internal-time-till-roenneber/
8. Roenneberg, T., Daan, S., & Merrow, M. (2003). The Art of Entrainment, 18(3). doi:10.1177/0748730403253393
60. 9.
Sources 2
Fackelmann, K. (2007). Study: Sleep deficit may be impossible to make up. USA Today. Retrieved from http://
www.usatoday.com/news/health/2007-11-25-sleep-deficit_N.htm
10. Hublin C, Kaprio J, Partinen M, Koskenvuo M. (2001) Insufficient sleep: a population-based study in adults. Sleep, 24: 392–
400 cited in Wikipedia, replace w other data
11. Toh, K. L., Med, M. I., Uk, M., & Genet, H. (n.d.). Basic Science Review on Circadian Rhythm Biology and Circadian Sleep
Disorders, 662-668.
12. Psychomotor vigilance task. (2012, June 11). In Wikipedia, The Free Encyclopedia. Retrieved 10:24, June 22, 2012, from
http://en.wikipedia.org/w/index.php?title=Psychomotor_vigilance_task&oldid=497069857
Editor's Notes
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We spend a lot of effort being and recruiting talented people\n
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Sound like a launch you know? \n\n“the ability [as the same study put it] to understand, adapt, and plan in rapidly changing circumstances”\n\n
Need to be able to explain this test\n
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How many of us get a full night's sleep?\n
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Besides, do you really take the weekend off?\n
Why are the groups pre-sorted even on B? \n
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We've shown that:\n* sleep dep is bad\n* much population gets sleep dep from normal sleep schedules\nWe need to show:\n* this can't be fixed\n
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Light cycle is basically consistent per external day\n\n
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Mention scn here\n
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Citation on better performance comes from study of students, at least for now\n