New Biological Rhythms (2) Flashcards
What two things are biological rhythms governed by?
- endogenous pacemakers: the body’s biological ‘clocks’
- exogenous zeitgebers: external cues from the environment
What are circadian rhythms?
- a type of biological rhythm
- last for around 24 hours, such as the sleep-wake cycle and body temperature
What did Siffre find about our circadian rhythms?
- spent two months in the caves of the Southern Alps
- no access to external sounds or clocks but had adequate food/drink and lived by candlelight
- found his ‘free running’ biological rhythm settled down to one that was just beyond the usual 24 hours
- found similar results when he repeated the study 6 months later
- showed that our circadian rhythms have a biological basis because they stayed more or less the same
- must have been governed by internal cues due to the lack of exogenous zeitgebers
What research shows evidence for the negative effects of jet travel?
- Recht found decreases in physical abilities and skill when baseball players suffered from jet lag
- found that players won 44% of games when travelling to the East to West coast but only 37% when travelling West to East
- deterioration in performance can be explained in terms of disruption to their biological rhythms
What research shows evidence for the negative effects of shift work?
- physical and psychological effects of shift work are known as shift lag
- Tilley et al. studied performance and sleep quality in 12 male shift workers, whose shift patterns frequently changed during the course of the 3 week study
- when working nights, although workers slept during the day, the sleep was shorter and often disrupted
- as the number of night shifts increased, their reaction times and decision making abilities were impaired
What was the background of Czeisler’s study?
- previous research showed rotating shift workers were dissatisfied with their schedules that violate circadian rhythms
- C suggested strategies to deal with this can never be truly effective as they don’t work within the endogenous pacemakers that control the circadian sleep-wake cycle
- if shift work patterns were designed to fit these rhythms, workers would be less likely to experience the effects of sleep deprivation
- this area of research has become very important as the need for shift work has dramatically increased
What sample did Czeisler use?
- 85 rotating shift workers at a mineral mining plant in Utah
- all male
- control group of 68 on shifts that didn’t rotate
What shift patterns did the control and experimental groups have?
control: either worked day shifts or swing shifts without rotation
experimental: originally worked in a phase advancing rotation but then changed to a phase delay system
Why were phase advancing and delaying systems investigated?
- at the time, researchers believed our natural sleep-wake cycle worked on a 25hr cycle, so a phase delay system would be 7hrs out of sync with our circadian rhythm, compared to a phase advance system which would be 9hrs out of sync
- also links to jet lag research: phase delay is like travelling east to west, and phase advance is vice versa
What was the first element of Czeisler’s procedure?
- each worker completed a job description and health indices questionnaire and a sleep-wake and schedule preference questionnaire
What were the results of Czeisler’s first questionnaire?
- 84% participants responded
- those on rotating shifts reported significantly more problems with sleep: 29% had fallen asleep at work at least once in the past 3 months
- commonly reported that their schedules changed too often
- 81% said it took 2-4 days to adjust their sleep pattern
What was the second element of Czeisler’s procedure?
- new shift pattern introduced: the phase delay patternx
- 33 continued to change every week whilst the others moved to a 21 day pattern
- three months later, completed a questionnaire about the move
What were the results of Czeisler’s second questionnaire?
- workers preferred the new phase delay system
- significant reduction in complaints by those moved to a 21 day rotation
- those on 21 day rotation had increased scores on the schedule satisfaction index and health index
- production of potash harvesting increased significantly
How can the effects of shift work be improved?
- decreasing the no. of night shifts in a row
- avoid extended work hours
- sleep well on days off
- avoid shifts that start at 5-6am
- sleep inducing drugs
How can the effects of jet lag be improved?
- melatonin supplements
- staying hydrated
- simulate new time/schedule
- controlled exposure to light
- gentle exercise
