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Describe Czeisler et al ( 1990) case study

"Exposure to bright light & darkness to treat physiologic maladaptation to night work " Changed the level of light to which night workers were exposed - bright light during 8 hrs work & darkness for 8 hrs during sleep hours alllowed the body's circadian rhythm to adjust to night shift in 2/3 days


Problems of Czeisler et al (1990)

Shiftwork disrupts biological rhythms & following accidents occurred between 1-4am - Bhopal (chemical accident) , 3 mile island(nuclear accident) & Chernobyl ( nuclear accident)


What were the instructions in the case study ( Czeisler)?

-asked to stay in complete darkness from 9am to 5pm. -controls were given no specific instructions. -all completed cognitive tasks hourly otherwise would do own work. -control group worked during night in ordinary indoor light(150lux). -experiment group worked under bright illuminations of 7000-12000lux equivalent to every morning light


What did Czeisler 1990 make sure participants do?

-8 men (22-29) , none had worked regularly on night shifts before. -no sleeping dissorders. -none had been jet lagged in the past 6weeks


What was the method of Czeisler ?

2 week Experiment , 5 control condition & 5 treatment condition


What did Czeisler believe about shift work ?

That shift work environments that are warm and dimily light are counter productive & belived that exposure to bright light at night & darkness during day could help shift workers resynchronise better


Describe what happened in the 2 week of Czeisler study

1st week base line study & 2nd week night shift work -men lived at home buy reported for work at lab each night in the 2nd week , 2 men one control , one treatment did not conform to protocol so their results were excluded


What was the problem that Czeisler found out about shift work ( another study)?

7.3 million Americans work at night but research has shown that a complete adaption of endogenous circadian rythmms does not occur even after years of shift work


What were the results ?

(Treatment study slept 2hrs longer than control) 1) significant shift in body temp nadir between 1&2 between control & treatment condition (the endogenous pacemaker was adapting ). 2) behavioural changes- same behaviour but shown an hour later in treatment conditions. 3) alterness & performance -the treatment conditions were more alert than control by end of week 2


What were procedure meassurmensts ?

Measure body temp ( typically when circadian body temp is at lowest 4:30am). -blood samples from were collected every 15-25mins on random. -alertness was asssed 3 times an hour using an calculator & subjective awareness. -urinary excretion rates. -plasma cortisol concentrations


What was the evaluation- strengths ?

This is a well controlled experiment that contained many different physiological measures to isolate cause and effect , overall they showed endogenous pacemaker is hard to shift but they are things we can do to adapt


Evaluation. Weaknesses?

1) biological reductionism - this portrays the body as a machine like which automatically adjusts to natural zeitgebers such as light & social explanations such as more noise in daytime,stress could occur from loss Contanct family 2) Czeisler et al claim that questions still to be answered concern - variability between individuals (age/sex) & duration / intensity of light needed for optimal adaption to night work


What is in the conclusion?

They demonstrated that maladaption to night shift work can be treated successfully with property times exposure to bright light during the night shift work and darkness during daytime sleep