Shift Work and Shift Lag & Jet Travel and Jet Lag
Shift Work and Shift Lag
> Night workers are required to be alert at night & so must sleep during the day, which is the reverse of our natural rhythms & out of line with most of the available cues from zeitgebers.
Decreased alertness -
> BOIVIN ET AL. found nightworkers often experience a circadian 'trough' of decreased alertness during their shifts, which occurs between midnight (cortisol levels lowest) & 4am (core body temperature at its lowest).
Sleep deprivation -
> Workers who sleep by day often experience sleep problems because when they finish work it's daytime & there are other interruptions (outside noises) & daylight reduces sleep quality.
> TILLEY AND WILKINSON found that daytime sleep is typically between 1 & 2 hours shorter than a nocturnal sleep period and that REM in particular is affected.
> Poor quality daytime sleep makes it more difficult for shift workers to stay awake at night, especially when they hit the circadian 'trough'.
Effects on health -
> There's a significant relationship between shift work and organ disease.
> KNUTSSON ET AL. found that people who worked shifts for more than 15 years were three times more likely to develop heart disease than non-shift workers.
> MARTINO ET AL. linked shift work to a range of organ diseases, including kidney disease. (may be due to direct effects of desynchronisation or the indirect effects, such as sleep disruption).
Jet Travel and Jet Lag
> Our biological rhythms aren't equipped to cope with sudden & large changes - (jet travel).
> It's estimated that the dorsal portion of the SCN takes several cycles to fully resynchronise to abrupt large changes in environmental time - a process we experience as jet lag.
> WINTER ET AL. calculated that it's the equivalent to one day to adjust to each hour of time change.
> Symptoms of jet lag = loss of appetite, nausea, fatigue, insomnia & mild depression.
Performance decrement -
> In American the west coast is 3 hours behind the east. RECHT ET AL. analysed baseball teams on each coast over 3 years & found that teams who travelled east to west won (on average) 44% of their…