copyright catherine m. burns 1 circadian rhythms and shiftwork text chapter 13 p. 343-348
TRANSCRIPT
Copyright Catherine M. Burns
1
Circadian Rhythms and Shiftwork
Text Chapter 13 p. 343-348
Copyright Catherine M. Burns 2
Sleep Loss
Have you ever pulled an “all-nighter”? Flown the “red-eye” flight? How did you feel afterwards?
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Who is sleep deprived right now?
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The Epworth Sleepiness Scale
A standardized scale used by sleep experts Assess your chance of dozing
0 would never dose 1 slight chance of dozing 2 moderate chance of dozing 3 high chance of dozing
Scale: National Sleep Foundation
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Sitting and reading? Watching television? Sitting still in a public place (theatre or movie)? Passenger in a car for an hour? Lying down in the afternoon? Sitting and talking to someone? Sitting quietly after lunch? In a car while stopped in traffic?
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Causes of Sleep Loss
deliberately staying awake sleeping at unnatural times
during daylight counter to one’s circadian rhythms
sleeping with the effects of caffeine or alcohol
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Circadian Rhythms
natural physiological cycle the body goes through every day
temperature, metabolism, and chemical level changes
low temperature in the morning rises during the day then drops (6:30-6:30 roughly)
slightly longer than 24 hours People with circadian rhythm disorders
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Body Temperature
6am 6pm
36.5
37.0
Text p. 345 Figure 13.5
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Circadian Rhythms
Cycle correlates with sleepiness sleep efficiency (how long we sleep) performance
Strong correlation with errors and accidents
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Performance
6am 6pm
6am 6pm
6am 6pm
6am 6pm
Psychomotor Performance
Symbol cancellation
Reaction Time
Digit summation
Text Figure 13.6 p 346
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Circadian Rhythms and Driving
When would you expect more accidents? With the spring time change? With the fall time change? Why?
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Accidents in Canada 1991-1992
Spring Fall
Day of the change
Day before, of, after the change
Source: Sleep thieves
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Accidents in Israel
# of
accidents
Time4am 4pm
Source: Sleep thieves,
Stanley Coren
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Circadian Rhythms and Driving
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Circ Rhythms and Accidents
Which of the cases we’ve studied could have been influenced by circadian rhythms?
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Effects of Sleep Disruption
impaired judgement reduced ability to learn reduced ability to store new material inability to plan
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Assessing Sleep Debt
Do you need an alarm clock to wake up? Do you hit the snooze to get a few more minutes? Getting out of bed is a struggle Sleeping through the alarm Sleeping longer on weekends than during the week Getting sleepy sitting and reading Dozing off when watching TV? Feeling dozy after lunch Drink more than four cups of coffee or tea?
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Solutions
get more sleep! some sleep is better than no sleep napping (even 15 minutes) is proven to
improve performance caffeine for short runs avoiding shiftwork or planning it properly
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Shiftwork
Circadian Desynchronisation: Shiftwork is counter to circadian rhythms
Issues: alertness, hunger patterns, urinary patterns, quality of sleep, cardiac health, asthsma
Solutions permanent assignment (people don’t usually like this) slow rotation fixed for 2-3 weeks then time to resynchronize between
shifts
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Shiftwork
Shifts should rotate later “delay” Eg. 12am-8am then to 8am-4pm. Due to length of rhythm it is easier to adjust
to a later shift than an earlier one Shifts are easier for younger person Older people have less physiological
capacity to adapt
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People who should not do shift work
Over 40 Cardiac problems Asthsma Diabetes Epilepsy Past experience with depression
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Jet lag
UK statistics show that most holiday accidents happen on the drive home from the airport
Drivers 4am-6am have 13 TIMES the accident risk
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Circadian Resynchronization
Can be artificially stimulated Cues:
Light/dark Food Activity
Exposure to bright light during “daytime” Full spectrum lights, melatonin?
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Melatonin studies
Unlike mice, people who are totally blind cannot set the clock in their SCN. As a result, their circadian rhythm drifts out of phase with the actual cycle of day and night. These people often are bothered by feeling sleepy during the day and wide awake when they want to be asleep at night. A recent (12 October 2000) report in the New England Journal of Medicine tells of a group of blind people who were able to set their clocks with the help of a dose (10 mg) of melatonin at bedtime. However, this treatment worked only when the subject's circadian rhythm had drifted so that the normal rise in melatonin from the pineal gland was occurring in the early evening; that is, the dose of melatonin had to be given when it could boost the endogenous level of the hormone.
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http://www.sleepfoundation.org/nsaw/sleepiq99i.cfm