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.

1. 💤
Sleep!
Alex Koppel - @arsduo

2. Why talk about sleep?
• Our job is to solve problems
• Sleep is tied to how well we can think
[4]

3. Also
We have a macho culture about sleep

4. How do we get the
most out of ourselves?

5. Part I
Less Sleep, No Sleep
and what happens to you

6. Sleep Deprivation
Just stay up till it's done

7. sleep(0)
• Sleep deprivation hurts your ability to
think
• “This deactivation is greatest in those brain areas
sustaining higher cognitive performance and
situational awareness.”
• 25% mental decline / 24 hours awake
Source: [3]

8. Just how bad?
~66% performance loss after 3 days
Source: [3]

9. Not sleeping is a bad idea
(Not a surprise)

10. Sleep Restriction
"Just one more episode, then I'll sleep"

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?

13. Question
Is sleeping 6 hours a night reasonable?

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]

20. Is sleeping 6 hours a night
reasonable now?

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]

24. Incomplete recovery
Baseline
(min)
Source: [2]

25. Part II
Whys and Wherefores
Why it's so hard to get enough sleep

26. Late to bed, early to rise
• Sleep restriction is a common problem
• Why is getting enough sleep so hard?
• What can we do about that?

27. Chronotypes
Our sleep patterns

28. Sleep pattern spread
Wakeup time for 7
8 AM 10 AM
hours sleep:
Source: [6] p. 13

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?

33. Body Clocks
The Art of Entrainment

34. Here’s where it gets complicated
(and interesting)

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

36. Internal Day
When you wake up When you're asleep
(hopefully)
Source: [6] p.121

37. Internal Day
When you wake up When you're asleep
(hopefully)
Source: [6] p.121

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?

40. Solution!
• Wake later
• Your inner evening happens in the dark!

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

47. Part IV
Conclusion
Wake up, it's almost over

48. Consequences
• When people's work aligns with their cycles,
they perform better
Source: [6] p.112

49. In practice
• Respect your own biology
• Get enough sleep!
• Encourage your team to sleep
• Flexible start times

51. Thanks!
@arsduo
@6Wunderkinder
http://dev.6wunderkinder.com

52. Eurucamp 2012
2012.eurucamp.org

53. Appendix
Sources and other material

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?

58. Other results similar
Digit substitution, addition/subtraction
Source: [1]

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