10. Disruption of Biological Rhythms - Jet Lag/Shift Work

• 1. Disruption of BRs - Jet Lag + Shift Work

  Environmental factors influencing BRs change slowly, allowing endogenous pacemakers keep up.

  • if exogenous zeitgebers change quickly, problems occur - e.g. slow reaction time.
• 2. Disruption of BRs - Jet Lag + Shift Work

  Shift Work:

  • bodies working directly against 24hrs CR of S/W cycle.
  • working against cycle leads to issue of desynchronisatio; when endogenous pacemakers + exogenous zeitgebers not in sync.
• 2a. Disruption of BRs - Jet Lag + Shift Work (Evaluation)

  Shift Work - Evaluation:

  Physical Issues -

  • shift workers tend come from lower class groups = poverty/deprivation may be factor.
  • nutrition/diet; restricted access to fresh meals, increased intake of caffeine may be factor.

  Emotional/Social Issues -

  • household issues related to socioeconomic class/poverty.
  • less time available to maintain relationships.
  • stress from repetitive/long hrs, increase house tensions.
• 3. Disruption of BRs - Jet Lag + Shift Work

  Jet Lag:

  • different time zones.
  • caused by melatonin release (endogenous pacemakers) out of sync w/ new environment (exogenous zeitgebers) = fatigue, insomnia, anxiety.
• 3a.Disruption of BRs - Jet Lag + Shift Work

  Jet Lag, 2 effects:

  1. phase advance - getting up/going bed earlier than usual (flying west-east).
  2. phase delay - getting up/going bed later (east-west).

  • easier adjust phase delay bc lengthens day.
  • Siffre and Aschoff + Weaver demonstrate internal rhythm greater than 24hrs, can cope w this.
  • phase delay brings exogenous z closer in line w/ endogenous pacemakers; phase advance = further away.
• 3b. Disruption of BRs - Jet Lag + Shift Work

  Research Jet Lag - Recht (1995):

  • performance of Major League Baseball teams + impact of jet lag.
  • teams traveled E-W, won 44% games.
  • W-E, won 37% games.
  • Home teams won 56%, chances of wining depended on opposite team travel.
• 3c. Disruption of BRs - Jet Lag + Shift Work

  Research Jet Lag - Cho (2001):

  • air cabin crew, reduction in temporal lobe + memory function among those who regularly flew across time zones.
• 3d. Disruption of BRs - Jet Lag + Shift Work

  Reducing Symptoms of Jet Lag:

  Melatonin Supplement -

  • chemical secreted at night, enables us to switch off wakefulness cues of daylight.

  Klerman (2009):

  • taken before bedtime in new time zone effective for sleep before body clock normally allow.
  • pure melatonin tablets not yet met EU safety regulations, trials using synthesised versions lack ecological validity.
• 3e. Disruption of BRs - Jet Lag + Shift Work

  Reducing Symptoms of Jet Lag:

  Meal Times:

  • meal t = exogenous z (or social cue), helps synchronise CRs + inform endogenous pacemakers what time it is.
  • Fuller (2008) - fasting before travel, eating in new time zones = alter BRs.
  • Saper (2008) - as well as main ‘master’ clock in SCN, also ‘feeding clock’, depends on food intake; in mice, feeding clock overrides SCN = kept awake until food.
• 3f. Disruption of BRs - Jet Lag + Shift Work

  Reducing Symptoms of Jet Lag:

  Light Exposure -

  • Burgess (2003), light exposure before E-W flight decreased time needed to adjust to local time upon arrival.
  • suggests light exposure before flight allow travellers arrive w/ CRs already set to local time.
• Disruption of BRs - Jet Lag + Shift Work (Evaluation)

  Jet Lag (Evaluation):

  Travel Anxiety -

  • people anxious about flying; affect ability to sleep.
  • anxiety also triggers fight/flight response, procures symptoms similar to jet lag.

  Nutrition Before/During Flight:

  • passengers may have alcohol; induces sleep and/or prevents rest.
  • may eat at unusual times = digestive issues.
  • caffeine increase may have similar effects.