Sleep!

My presentation from Railsberry 2013, in which I talked about the effects of sleep loss on the brain and on the biology behind our sleep cycles.

Transcript

1. Sleep! Alex Koppel - @arsduo
2. Me
3. Sleep on Rails
4. Sleep in Rails • Rails 4 on Ruby 2.0 refines Kernel#sleep • Accepts negative argument in controllers • Only known use for refinements
5. Sleep in Rails around_filter :deliver_request_fast def deliver_request_fast received_at = Time.now yield # go back and deliver the results immediately sleep(received_at - Time.now) end
6. Time Travel is Webscale
7. Real Sleep
8. Why?
9. We are thinkers! • Our job is to solve problems • Sleep directly impacts the brain • How we sleep affects how we code
10. We have a problem
11. We have a problem • Huge population suffers from insufficient sleep • Estimated 20%+ of Americans affected • Wanting more sleep, not getting it • Frequently tired Source: [10]
12. No no no no We must kill our macho culture about sleep Source: [13]
13. tl;dr • Lack of sleep impairs your thinking • Our natural sleep cycles arise from biology • Therefore: we must support sleep
14. Science ahoy!
15. Sleep is complicated
16. Less Sleep, No Sleep and what happens to you
17. Baseline • Most people need 7-8.5 hours of sleep Source: [4], [6]
18. 0.hours.sleep • Sleep deprivation hurts your ability to think • “This deactivation is greatest in those brain areas sustaining higher cognitive performance and situational awareness.” • Not a surprise Source: [3]
19. Sleep Restriction "Just one more episode, then I'll sleep" or, “Time for crunch mode!”
20. def chronic_sleep_restriction • Getting reduced sleep over repeated nights • Estimated 20%+ of Americans affected Source: [10]
21. Effects • Sleep restriction reduces brain function
22. Effects • Sleep restriction reduces brain function Surprise!
23. Less sleep, less brain • Sleep restriction reduces brain function • Cumulative effects over time
24. Less sleep, less brain • Sleep restriction reduces brain function • Cumulative effects over time • Proportional to how much sleep lost
25. Science! • Let's quantify this • Common test in sleep research: PVT • Measures reaction time, sustained attention • See appendix A
26. Source: [1] Charts and Graphs Y axis: failures to respond to visual prompt inside time window X axis: experiment time
27. PVT Results Sleep deprivation (0 hours sleep): errors rise quickly 1 tick = 2 days Source: [1]
28. 8 hours sleep/night: nearly no change Source: [1] 1 tick = 2 PVT Results
29. 4 hours sleep/night: sleep-deprived in a week Source: [1] PVT Results
30. 6 hours sleep/night: sunk by week 2 Source: [1] PVT Results
31. PVT Recap <= 6 hours sleep: Bad shit happens. Source: [1]
32. Other tests agree • Higher-level tests also show similar effects • Proportional, cumulative effects • Impaired learning • See appendix Source: [1]
33. Ok, but... • Can’t you just sleep it off over the weekend?
34. Apparently not • The brain adapts to less sleep • This persists at least several days after restriction stops • Recovery sleep is physically different Sources: [2], [4], [9]
35. Another study Source: [2]
36. Incomplete recovery Source: [2] Lowest baselin
37. Analysis • Even the 7 hour group wasn’t back to original state after 3 nights of full sleep • A weekend isn’t long enough • Obviously you recover eventually Sources: [2], [4], [9]
38. It’s hard! • Even knowing all this, getting to sleep is tough • Why are we so bad at staying rested?
39. Sleep disturbed • Many things can affect sleep • Alcohol and other drugs • Exercise • Stress and emotion • Diet • Willpower • Kids • Sex • Webcomics
40. Put those aside • Let's just look at natural sleep rhythms • Healthy, drug-free people don't get enough sleep either!
41. Chronotypes Our sleep patterns
42. Chronotypes • A way to group sleepers • The mid-point of our natural1 sleep cycles • Regardless of length • For most, 3.5-4 hours into sleep 1 Imagine a quiet 3 week vacation at home, sleeping and waking when you want.
43. In the Population Wakeup time for 7 8 10 Source: [6] p. 13
44. Alternately put Source: [6] p. 13 Over 50% of the population wakes btw 8 and 11 AM Only ~33% naturally wake up before 8 AM
45. Especially for us Sleep midpoint (hour) Source: [6] p. 101 Younger populations tend to later sleep
46. • Much of society starts up between 8 and 9 • We're asked to live contrary to our biology Yet
47. Social Jet Lag • Society time != body time • Expressed through sleep loss • Like traveling by plane every day • 40+% of Central Europeans off by 2+ hours Source: [6] p. 149
48. Objection!
49. Aren’t we just lazy? If we want it enough, we can wake earlier
50. No • Our bodies sync their clocks with the sun • Most people run longer than 24 hours • This “entrainment” tends toward later sleep • Sleep cycles are hard to change Source: [6] p.117-128
51. Conclusion Wake up, it's almost over
52. To repeat • Sleep cycles arise from biology • (In an otherwise constant environment) • We can't (easily) control / change this
53. And • Getting less sleep damages thinking • Damaging thinking is damaging coding Source: [6] p.112
55. • Respect your own biology • Get enough sleep! • It's difficult, but worth it
56. Managers! • Encourage your team to sleep enough • Let people follow their rhythms • Don't worship crunch time
57. Sleep has real benefits • Health • Memory • Reducing stress • Etc.
59. http://www.amazon.com/Internal-Time-Chronotypes-Social-Youre/dp/0674065859 Highly recommended
60. Thanks! Alex Koppel - @arsduo
61. We're hiring!
62. Thanks! Alex Koppel - @arsduo
63. Appendix A All the stuff I couldn’t fit in the main talk
64. 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
65. Sleep Deprivation
66. Just how bad? ~66% performance loss after 3 days Source: [3]
67. Sleep Restriction
68. 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]
69. Science time! • Psychomotor vigilance test (PVT) • Subjects respond to a visual stimulus • Measures attention and response time • Also lapses (response > 500ms) • Used by NASA and sleep researchers Source: [12]
70. Other Test Results • Sleep restriction impacts shown on other tests • Higher-level functions tested than just response time • Tests with learned skills Source: [1]
71. Matching digits to symbols 8 hours: learning bonus 6 hours: no learning 4 hours: got worse Source: [1] Digit Symbol Substitution Task
72. Similar results Source: [1] Sustained Addition and Subtraction Task
73. Analysis • Sleep restriction effects more manageable with complex tasks • BUT no gains from learning • We need to learn to succeed • Interesting question: would gains appear after recovery sleep? Source: [1]
74. Body Clocks The Art of Entrainment
75. Here’s where it gets complicated (and interesting)
76. Internal Clocks • All humans (organisms) have internal clocks • Few run exactly 24 hours per cycle • On average slightly longer Sources: [11], [6] p. 1, 118-127
77. But if our clocks aren't 24 hours...
78. Won’t craziness ensue? When you wake up
79. Half
80. and half
82. Light • Our bodies use light to sync with the world • Light at different times shifts our sleep/ wake cycle • Longer days lead to later sleep patterns Source: [6] p.117-128
83. Internal Day • We each have an internal "day" • From one waking up to the next • Light affects us differently at different times of our days
84. Internal Day When you wake up When you're asleep (hopefully) Source: [6] p.121
85. Internal Day (hopefully) Source: [6] p.121 When you wake up When you're asleep
86. Entrainment • Light in the inner morning shortens the day • You sleep earlier • Light the in inner evening lengthens it • You sleep later • The body mixes both to get the right adjustment Source: [6] p.117-128
87. Example • Your day is too long (say, 24.5 hours) • You want to compress your day (sleep sooner) • So...what do you do?
88. Solution! • Wake later • Your inner evening happens in the dark! • Compression > expansion • A shorter day (24 hours)
89. More proof Waking times among a homogeneous population (Germany) in 1 time zone are controlled by the Source: [6] p.158
90. Bringing it all back home • Most people have a longer clock • So most people ought to wake later • And that's what we saw earlier!
91. Appendix B A few webcomics
92. http://www.qwantz.com/index.php?comic=136
93. http://www.qwantz.com/index.php?comic=1191
94. Ryan North on sleep What's your sleep routine like? When I was a kid I had to get up at 6 to catch a 7 AM bus into school, and once I started grad school I relaxed that to 7 AM. So I'm usually up at 7 sharp (alarm set so I can hear the news) and then in bed when I start to get sleepy, which is normally between 11 and midnight. I really value my sleep. And I wish it were somehow super awesome to say "I really value my sleep." [emphasis added] http://lifehacker.com/5986982/im-ryan-north-creator-of-dinosaur-comics-and-this-is-how-i-work
95. http://xkcd.com/320/
96. http://xkcd.com/448/
97. http://www.phdcomics.com/comics/archive.php?comicid=1079
98. Sources
99. 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
100. Sources 2 9. 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 13. Alternative Sleep Cycles: You Don’t Really Need 6-8 Hours! Retrieved April 11, 2013 from http://www.highexistence.com/alternate- sleep-cycles/ Image credits: • welu-berlin. Brandenburger Tor. Retrieved April 21, 2013 from http://www.flickr.com/photos/welu/1345394487/ • Daj12192. Willis Tower. Retrieved April 21, 2013 from http://commons.wikimedia.org/wiki/File:WillisTower11.jpg • Mills, Dan. Hard at Work. Retrieved April 21, 2013 from http://www.flickr.com/photos/thunder/98937190/ • Munroe, Randall. Science. Retrieved April 11, 2013 from http://xkcd.com/54/. • Munroe, Randall. Hallucinations. Retrieved April 21, 2013 from http://xkcd.com/203/ • People in a meadow. Retrieved April 21, 2013 from http://www.yourwealthforlife.com/blog/how-to-enjoy-life-more/