shift work and sleep
The most common health problem reported by the shift workers is sleep disturbances.
- sleep disruption includes reduced sleep duration and/or sleep quality
- around 75% of shift working people are affected
- short sleep or poor sleep quality are thought to be associated with adverse health effects seen in shift work (1,2)
A deviation and sometimes the inversion of the sleep/wake cycle of a person affect the endogenous regulation of the "circadian" (of about 24 hours) rhythms of biological functions.
- shift work schedules often results in
- work during the biological night when the circadian system is promoting sleep and
- sleep during the biological day when the circadian system is promoting wakefulness
- this misalignment of circadian rhythms of body functions directly leads to impaired wakefulness and disturbed sleep (both in quantity and quality) (1,2).
Sleep quality
- is strongly associated with circadian rhythm disturbances.
- sleep episodes that end close to the circadian trough (e.g. - before starting early morning shifts) are often perceived as non-refreshing, and awakening is difficult.
- daytime sleep following a night shift normally has a short subjective sleep latency with relatively few awakenings throughout the sleep. However sleep ends prematurely after four to six hours (3)
Sleep duration
- a meta-analysis based on subjective sleep duration reported that
- daytime sleep following night work was the shortest (mean 5 h 51 min)
- longest sleep was seen after evening shifts (8 h 2 min)
- sleep before morning shifts is also limited (6 h 37 min) specially with an early start time (before 0600) or if preceded by an evening shift.
- in addition the following factors affects the sleep duration
- a short recovery time (<11 hours) between shifts
- speed of shift rotation
- slowly rotating schedules (e.g. - four to seven consecutive shifts of the same type) resulted in a slightly longer sleep duration (6 h 56 min) than did rapidly rotating schedules (e.g. - one to three similar shifts in a row) (6 h 31 min)
- several reviews which carried out an objective assessment of sleep duration with polysomnography showed
- daytime sleep after a night shift was around 5.0-5.5 h, and sleep periods before early morning shifts were 5.5-6.0 h
- in both instances stage 2 and rapid eye movement sleep was affected while slow wave sleep was unaffected
- early awakenings (as in the case of on-call work or before early morning shifts) is associated with suppressed slow wave sleep (3)
When shift work related sleep/wake problems are present for at least three month, it is referred to as “shift work sleep disorder” (SWD), which is a clinical circadian rhythm sleep disorder according to the international classification of sleep disorder (3)
Reference: