Disruption of biological rythems

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  • Research into the disruption of biological rythems
    • a biological rythem is a regular pattern of psychological, behavioral or cognitive activity
      • these include CIRCADIAN (every 24 hours) INFRADIAN (more than 24 hours) and ULTRADIAN (less than 24 hours)
      • on average we sleep 7.5 hours per night but the rapidly changing external world means out body clocks are becoming increasingly synchronized with the outside world
    • Jet Lag
      • caused by flying across time zones and involves a dislocation between the body clock and exogenous zeitgebers
        • reserch has found that the consequences of jet lag include: cognitive disturbances, memory problems, reduced alertness (SPITZER et al) and increased cortisol secretion, a stress hormone when jet lagged (CHO)
        • it has been suggested that jet lag is worse west to east as it involves phase advance
          • RECHT, LEW AND SCHWARTZ-  longitudinal study of baseball players travelling around USA for games. found that those flying east to west won 44% of games in comparison to whose who flew west to east and won 37% of games
            • small difference/ ignores individual differences but length of study (3yrs) should even this out.
            • supported by O'CONNOR who found that athletes flying west for training suffered a day less than those flying east
      • other factors ifluencing jet lag include-
        • PERSOANLITY- evidence that some people are more 'phase tolerant' and deal better with jet lag.
        • AGE- Sack found evidence that jet lag decreases with age
      • to reduce jet lag COREN suggested:
        • adjust travel behaviour before flight so body clock is alredy synchronised when you arrive
        • avoid caffeine and alchohol
        • take melatonin; supported by BEAUMONT who found that a melatonin pill at night 3 days before travel sped up resynchronisation to new zeitgebers
    • PHASE DELAY- when the day lengthens and you have to delay sleep time- easier to adjust to (east to west)
    • PHASE ADVANCE- day shortens and have to advance sleep time- more difficult to adjust to (west to east)
    • Shift Work
      • typical working day is divided into 3 shifts: 12am- 8am/ 8am-4pm/ 4pm-12am
      • COREN- 1in5 workers in america are on shift work
      • consequences of shift work include increased accidents and risk of heart disease:
        • KNUTSON- working the night shift increased workers chance of heart attack by 30%
        • CZEISLER- found four fold increase in chance of accidents in police on the night shift
        • KOBO- found four fold increase in chance of prostate cancer in males working the night shift
      • forward shift rotation was developed and involves moving workers shifts forwards not backwards so they have phase delay which is easier to deal with then phase advance
        • CZEISLER- introduced forwards hift rotation to workers who worked 7 day backwards shifts and complained of stress, difficults sleeping, and low productivity. after 9 months of 21 day forward shifts workers reported reduced stress and sleeping problems and increased productivity
          • supported by GORDON- who found a 30% reduction in sleeping on the job and 40% reduction in accidents when he moved Philadelphia police officers onto an 18 day forwards shift
      • other methods to cope with the consequences of shift work include
        • permanent shift work- PHILLIPS - proved unpopular with workers
        • planned napping- SACK- proven to increased performance but unpopular with workers and managers
          • rapid rotation- where the shift is changed so often the workers doesn't have chance to sync their body clock- COREN challenged the success of this method


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