Consequences of Disrupting Biological Rhythms.

Inuit eskimos have regular sleep/waking cycles, even thought they have continuous daylight in summer and darkness in winter,
For them, social rhythms of life are the dominant zeitgebers.

Desynchronisation - occur at unrelated times.

The dislocation of physiological rhythms from the outside world, which lasts as long as it takes for the body to resynchronize.
Winter et al suggested that it takes a day to adjust to each hour.

Symptoms include: Appetite, nausea, fatigue and disorientation.
It is believed if you follow the local zeitgebers it's easier to adjust than following your biological clock.

Takahashi et al (2002) melatonin speeds up resynchronisation of biological rhythms after an 11 hour flight and reduced the symptoms of jet lag.

The quickest way to resynchronize is to follow the meal times and social patterns of the new country rather than your own.

Blakemore et al (1988) Taking a melatonin supplement pill every evening can help reduce jet lag.

Phase delay --> East to West --> Body clock ahead of local time. (Easier to adjust)
Phase advance --> West to East --> Body clock behind local time. (Harder to adjust) 

Psychologists often study American Major League Baseball teams who travel from coast to coast to see the effect of jet lag.
The West Coast of America is three hours difference to the East Coast.
If East Coast teams play on the West Coast their clocks go backwards (delay)
If West Coast teams play on the East Coast their clocks go forwards (advance)

Recht et al (1995) Analysed US baseball results over a 3 year period.
                               The teams that travelled East to West won 44% of their games.
                                West to East dropped to 37%

Classically divided into three 8 hour shifts. 12-8, 8-4, 4-12.
Switching shifts disrupts links between external zeitgebers (light/dark, meals, social)

At midnight our cortisol levels are at their lowest and at 4am body temp lowest.
People who sleep during day may have trouble doing so because of external distractions. It is often between one and two hours less sleep than if you slept at night and REM is most affected.

IF you have poor sleep during the day, you will have trouble working at night particularly during the circadian trough which reduces alertness.

Knutsson et al (1986) people who work 15 hours or more were 3 times as likely to develop heart disease than non-shift workers.

Martino et al (2008) -found link between shift work and a range of organ diseases
                                   including kidney disease.

Many shift patterns require a change each week which doesn't give us time to readjust.
They are in a permanent state of jet lag which impairs performance and increases stress. The backward shift movement is the same as travelling west to east.

Nuclear Accidents; Chernobyl and Three Mile Island occured because of decision failings during early hours of the morning. Performance is lowered at times when biological rhythms are pushing for sleep.

Czeisler- Persuaded company to change phase-delay system; moving shifts forward each time and to increase rotation from 7 to 21 days.
After 9 months, worker satisfaction increased and factory output was higher.

Coren-Culture shift at start of the 20th century, when lighting became widely available. Factories could operate around the clock and it's now socially acceptable to be out later,
He thinks we sleep an hour and a half less than a century ago and so many of us are in a constant state of sleep deprivation.

Research FIndings- This research is consistent evidence for the idea that disrupting
                                  biological rhythms can have cognitive and emotional effects on 
                                  people, sometimes leading to serious consequences.
 

Methodological Issues- Generated by field studies that have high ecological validity
                                         but many confounding variables, like personality and 
                                         individual differences which aren't controlled.

Real Life Significance-  Thousands carry out shift work without any obvious effects
                                         on their cognitive abilities like attention or concentration or 
                                         emotional well-being.