Shift Work: Monk & Folkhard
From their research into shift work they identified two main types:
Rapid Rotation: Change shift times regularly
Slow Rotation: Change shift times every few weeks/monthly
It takes most people a week to adjust to a new sleep/wake cycle; so a rapid rotation would leave the worker is a constant state of disruption. However this may be better than permanantly altering a person's circadium rhythm, which a slow rotation may do.
Shift Work: Czeisler
He did a shift rotation study where workers rotated with the clock e.g. 6am-2pm, 2pm-10pm ect. He found that rotating with the clock is better than rotating against the clock. The study took place in a chemical plant where workers said they felt less tired rotating with the clock.
Shift Work: Boivin
He found that shift workers experienced a circadian low/trough with decreased alertness at around 4am. Artificial lighting is partially effective in resetting the rhythm and this can explain why so many night workers have this low. Being awake and busy at night doesn't move the rhythm because it is set by exposure to daylight.
Shift Work: Knutson
He found a relationship between shift work and heart disease. People who worked shifts for 15 years are three times moire likely to develop heart disease.
Shift Work: Tilley & Wilkinson
They found that workers who have to sleep by day have difficulties because their body clock doesn't adjust; this makes it difficult to sleep. There are also noises during the day. People who sleep during the day sleep 2 hours less than at night. This can affect REM sleep and lead to sleep deprivation.
Shift Work: Gordon
He found that air traffic controllers who rotate shifts every few days suffer a high rate of ulcers and increased blood pressure.
Shift Work: Evaluation
- There are individual differences in how people cope with disruption to their circadian rhythm. Some are less affected, especially those whose circadian rhythms are slow to adjust.
- Other factors could be involved e.g. shift workers experience social disruption as it is difficult to meet friends and spend time with family.
- The negative effects of shift work are supported by research.