Topic 2 environmental

Question 1

What is a circadian rhythm

Answer 1

Body cycles that last about a day. For example your sleep-wake cycle

Question 2

Describe phase delay

Answer 2

When you delay your bedtime

Question 3

Describe phase advance

Answer 3

When you advance your bedtime

Question 4

What is the aim of czeisler et als study on application of circadian principles

Answer 4

Investigate the effects of taking the properties of the human circadian system into the account in the design of work schedules (in relation to direction in which sifts are rotated and the interval between changes in the shifts that people work)

Question 5

Czeisler et al- describe the sample

Answer 5

• Facility specialised in potash production in Utah. Workers had phase advancing shifts.
• 153 male employees. 85 on rotating shifts, 68 act as a control group who’s shifts did not rotate. Worked either day shifts or swing shifts (4pm-12am)

Question 6

Czeisler et al- describe the method

Answer 6

• all workers and managers given an audio-visual presentation on basic properties of circadian sleep-wake cycle. Contained suggestions how to adjust sleep time to work schedule. Given educational booklet specific to their shifts.
• 85 workers on phase delay rotating shifts divided into two groups. 33 rotating every 7 days and 52 rotating every 21 days.
• workers given initial questionnaire on their sleep with their previous schedules (those on rotating experienced significantly more insomnia than those not on rotating)
• after 3 months given a questionnaire to fill in about which shift they prefer
• after 9 months personnel turnover and plant productivity analysed

Question 7

Czeisler et al- results

Answer 7

• significantly more workers preferred the new phase delay schedule of rotating shifts compared to their old phase advance schedule of rotating their shifts
• 21 day group significantly more satisfied with their schedule than the 7 day group. Also found significantly increased scores on a health index.
• 21-phase delay staff turnover reduced to the same range as the control group of non-rotating shift workers
• significant increase in the rates of both potash harvesting and processed potash production after the introduction of the new 21-day phase delay rotation schedule

Question 8

Name the 4 additional studies

Answer 8

• siffre (living underground)
• preckel et al (German high schools)
• melatonin supplements
• light box treatment

Question 9

Describe the additional research by siffre

Answer 9

• siffre lived in a cave for 2 months with only a light bulb for light
• he told his team when he woke up, are and when he was going to sleep (they kept a record of these)
• what he found:
• his body followed a daily sleep-wake cycle
• a cycle of 24hours + 30min
• what does this show:
• humans have an internal body clock independent of natural terrestrial day-night cycle
• light acts as a zeitgeber (brings our internal circadian rhythm in line with the cycle of light and dark above ground)

Question 10

Describe the additional research by preckel et al

Answer 10

• 272 students in the 9th and 10th grade from 5 German high schools given a chronotype questionnaire and a standardised cognitive test to complete in class
• parents of 131 of the students filled a questionnaire at home rating the child’s chronotype (lark or owl)
  Lark- bed before 11pm, wake up before 8am
  Owl- bed after 11pm, wake up after 8am
• found: being an owl was a significant negative predictor of overall GPA. Overall Owls had a lower GPA- suggests educational institutions favour students who naturally have a lark chronotype
• controlled: influences on maths, science and language GPA controlled for through use of a cognitive test

Question 11

Describe melatonin supplements

Answer 11

• SCN in brain instructs pineal gland to release melatonin
• this is a chemical that induces sleep, is inhibited by light
• Herxheimer and Petrie - found in 9 out of 10 studies conducted on jet lag, the use of melatonin was effective in reducing jet lag

Question 12

Describe light box treatments

Answer 12

• phototherapy (non-medical treatment)
• sit near a ‘light box’ which emits artificial bright light
• reduced melanin production, reducing the amount of drowsiness during a night shift
• affordable method which is effective within 15min
• costa et al found: bright light therapy improved physical fitness, sleep patterns, feelings of tiredness and performance. When testing on a group of nurses.