environmental topic 2- biological rhythms

Question 1

czeisler et al background

Answer 1

investigated rotation of shift work at a potash production in Utah, USA which used a rotating shift system where there were 3 work shifts:
the night shift 12pm-8am
the day shift 8am-4pm
the swing shift 4pm-12pm
the employees working shifts would change shifts every 7 days anticlockwise
the researchers aimed to take advantage of the longer than 24 hour endogenous circadian system

Question 2

czeisler et al sample

Answer 2

153 male employees with comparable jobs
85 male employees aged 19-68 on rotating shifts
compared against a control group of 68 employees aged 19-56 whose shifts did not rotate. These employees all worked either day shifts or swing shifts

Question 3

czeisler et al procedure

Answer 3

self reports were conducted to find out employees experiences of the shift system
all workers and managers given a presentation on the circadian sleep wake cycle including suggestions for how to adjust their sleep time to fit their work schedule
the 85 workers on rotating shifts were moved to a phase delay where 32 rotated every 7 days and 52 every 21 days
after 3 months he gave workers questionnaires about preferences, and measured personnel turnover and plant productivity after 9 months

Question 4

czeisler et al results

Answer 4

self reports found that 29% of employees on rotating shifts had fallen asleep at work at least once during the previous 3 months and 81% said it took 2-4 days to adjust after each phase advance
the post intervention questionnaires showed significantly more workers preferred new schedules.
those on 21 day rotations were significantly happier with this arrangement and productive. they had no more staff turnover than the control group

Question 5

czeisler et al conclusions

Answer 5

employees should rotate shifts forwards in a phase delay and not rotate work schedules with any greater frequency than in necessary.

Question 6

siffre
living underground

Answer 6

lived 40ft below earths surface in a cave in the alps for 2 months.
pitch black apart from a light bulb for the team on the surface to know when he woke up, ate and went to sleep
conditions below freezing with 98% humidity
his body followed a daily sleep- wake cycle where his body went through the same cycle every 24 hours and 30 mins, suggesting humans internal body clocks are dependant of the natural terrestrial 24 hour day/night cycle

Question 7

preckel et al
german high schools

Answer 7

investigated if society favoured larks with days being orientated towards early starts. sample of 272 students in 9/10th grade at 5 german high schools
chronotype questionnnaire and standardised cognitive test done in class
132 parents filled in a questionnaire rating their childs chronotype
found that being an owl was a significant predictor of overall GPA in maths, science and language

Question 8

Melatonin supplements

Answer 8

suprachiasmatic nucleus detects changes in light levels from the environment. when light is low it instructs the pineal gland to release melatonin which induces sleep

taking melatonin could help people when they need to sleep earlier than their body would naturally want to- good for phase advance

Question 9

light box treatment

Answer 9

phototherapy involves sitting near a light box emitting artificial light. this is used at the start of a night shift to reduce the production of melatonin - phase delay

costa et al- light therapy improved physical fitness, sleep patterns and performance as well as reducing feelings of tiredness for nurses working a night shifts compared to when working under normal light