The disruption of biological rythems 

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  • The disruption of biological rythems
    • a biological rythem is a reppeated pattern of behavioural, psychological or cognitive activity divided into circadian, infradian, and ultradian
    • the most significant disruptions brought around recently as technology has advanced are jet lag and shift work
    • Jet lag
      • caused by flying accross time zones when a dislocation occurs between the body clock and exogenous zeitgebers
        • research has found that jet lag can result in cognitive disturbances (Sitzer et al) with reduced alertness, clumsiness and memory problems
        • Cho- even found increased cortisol (stress hormone) secretion in jet lag suffers
        • it has been suggested that jet lag is worse west to east as it involves phase advance
          • evidence for this can be found in Recht, Lew and Schwartz study of american baseball teams who flew across time zones for games- they found that over 3 years teams flying west to east won 37% of games and those flying east to west won 44% of games
            • although this does ignore individual differences
        • jet lag can also affect sporting performace-  Sasaki- studied a vollyball team flying east to west who played badly for their first few games then improved
        • there are a number of factors influencing severity of jet lag
          • direction (east to west better)
          • Age- Sack suggested that jetlag decreases with age
          • also some individuals are more 'phase tolerant' and not as affected by jet lag
        • Coren- ways to reduce jet lag are avoiding alcohol, adjusting behaviour before flight, and taking melatonin
          • Beumont et al- found that melatonin taken at night 3 days before travel sped up resynchronisation
    • distrupting biological rythems can be divided into phase delay- where the day becomes longer and the individual has to delay their sleep- this is seen as the easiest to do.
      • phase advance involves a shorter day where an individual has to advance their sleep before they are even tired- seen as more difficult
    • Shift work
      • also involves a dislocation of our body clock and external environment
        • Knutson found that night shift work actually increased risk of heart attack by 30% in long term night workers
          • Kubo- found a fourfold increase in risk of cancer in male night shift workers
        • these health implications resulted in the introduction of forward shift rotation
          • Czeisler et al- in a utah chemical plant workers were on traditional backwards shift rotation with 7 days on each shift- workers repoted feeling stressed, sleeping issues and health problems-
            • Czeiser introduced forwards shift rotation with 21 days on each shift allowing the body clock to adjust properly- after 9 months the workers reported feeling less stressed and increased productivity
              • Gordon et al found similar results in a study on Philadelphia police officers- moved them from backwards shift to 18 days on forwards shift- led to 30% less sleeping on the job, and 40% reduction in accidents and an officers reported feeling less stressed and tired
        • other approaches to dealing with shift work are
          • permanent non-rotating shift work- allows the body to fully synchronize so the biological rythem is not disrupted
          • Rapid rotation- rotating shift patterns every 2-3 days to prevent the body clock resyncing so the circadian ryhthem is not technically disrupted
            • should technically work but Coren disagrees with its success


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