The Consequences of Disrupting The Consequences of Disrupting Biological RhythmsBiological Rhythms

The Effects of Shift Work and Jet LagThe Effects of Shift Work and Jet Lag Strategies to Minimise the effects of shift Strategies to Minimise the effects of shift

work and jet lagwork and jet lag

Lessons 7 and 8 – The consequences Lessons 7 and 8 – The consequences of disrupting biological rhythmsof disrupting biological rhythms

BATsBATs

AO1 -Identify and AO1 -Identify and describe at least describe at least two two consequences of consequences of disrupting disrupting biological biological rhythms (jet lag rhythms (jet lag and shift work) and shift work)

AO2 - Analyse and AO2 - Analyse and evaluate research evaluate research into the effects of into the effects of jet lag and shift jet lag and shift work on biological work on biological rhythmsrhythms

StarterStarterFill in the revision Fill in the revision

sheets about sheets about Bio-rhythmsBio-rhythms

Have you ever experienced any of the following:

Long haul flight

Stayed out late and then either

a.Had to get up early

b. had a long lie in?

How did it make you feel physically and mentally?

The causes of the accident are still described as a fateful combination of human error and imperfect technology.

Chernobyl nuclear disaster. 25-26th April 1986. 1.42am

The Exxon Valdez oil tanker struck Bligh Reef, off the coast of Alaska, at around 12:04 am March 24th, 1989. The accident resulted in the discharge of approximately 11 million gallons of oil 20% of the cargo, into Prince William Sound.

The third mate failed to properly manoeuver the vessel, possibly due to fatigue and excessive workload

What do these 2 disasters What do these 2 disasters have in common?have in common?

Both happened in the early Both happened in the early hours of the morning.hours of the morning.

Both were thought to be caused Both were thought to be caused by human error caused by by human error caused by disrupted biological rhythms!disrupted biological rhythms!

Watch the film clip.1. What effects can

shift work have?2. How can these

be reduced?

Shiftwork (shift lag)Shiftwork (shift lag)

Can have a Can have a harmful effectharmful effect on on health and well being.health and well being. Major cause is Major cause is disruption of circadian disruption of circadian

rhythmrhythm Body trying to function in complete Body trying to function in complete

opposite way to the instructions by opposite way to the instructions by Endogenous pacemakers and exogenous Endogenous pacemakers and exogenous zeitgebers.zeitgebers.

Being awake and active does not shift the Being awake and active does not shift the circadian rhythm as daylight re-sets itcircadian rhythm as daylight re-sets it

Circadian troughCircadian trough

Boivin et al 1996Boivin et al 1996 - Night workers - Night workers experience decreased alertness (at experience decreased alertness (at around 6am) – Circadian ‘trough’around 6am) – Circadian ‘trough’

Core body temperature takes even Core body temperature takes even longer to re-setlonger to re-set, which may affect , which may affect performance (below optimum performance (below optimum temperature for body functions temperature for body functions e.g.enzymes)e.g.enzymes)

Artificial lighting only slightly Artificial lighting only slightly effective in re-setting rhythmeffective in re-setting rhythm

Poor quality of sleep, partial sleep Poor quality of sleep, partial sleep deprivationdeprivation

More difficult to sleep in day:More difficult to sleep in day: Body clock doesn’t adjust Body clock doesn’t adjust

completelycompletely More noise and disturbances in More noise and disturbances in

the daythe day Daytime sleep 1-2 hours shorter Daytime sleep 1-2 hours shorter

than at nightthan at night REM particularly affected (Tilley REM particularly affected (Tilley

and Wilkinson, 1982)and Wilkinson, 1982)Consequence is sleep Consequence is sleep deprivationdeprivation

– makes circadian trough worse!– makes circadian trough worse!

Effects on healthEffects on health

Knutsson (1986)Knutsson (1986) – many studies – many studies show significant relationship show significant relationship between shiftwork and heart between shiftwork and heart disease.disease.

Those who worked shifts for Those who worked shifts for over over 15 years15 years 3x more likely3x more likely to to develop heart diseasedevelop heart disease

Commentary on ShiftworkCommentary on Shiftwork

Shiftwork has negative Shiftwork has negative effects effects

Individual differencesIndividual differences – Reinberg – Reinberg et al 1984et al 1984

Some workers are able to cope Some workers are able to cope with shifts because their with shifts because their rhythm changed lessrhythm changed less

Shift workers also experience Shift workers also experience social disruptionsocial disruption – can’t spend – can’t spend time with friends and familytime with friends and family

Gold et al 1992Gold et al 1992 - More problems - More problems with with rotating shiftsrotating shifts than fixed than fixed shifts (all nights)shifts (all nights)

Harmful effects can be Harmful effects can be reducedreduced

1.1. If rotating shifts are If rotating shifts are unavoidableunavoidable Phase delay Phase delay (get (get up and go to bed later) is less up and go to bed later) is less disruptive than disruptive than phase phase advance advance (get up and go to (get up and go to bed earlier)bed earlier)

2.2. Czeisler et al 1986Czeisler et al 1986 Bright Bright lights can mimic the effect of lights can mimic the effect of daylight and re-set body daylight and re-set body rhythms (rhythms (temp and cortisoltemp and cortisol) ) in 3 days (usually takes 9 in 3 days (usually takes 9 days to adjust to a phase days to adjust to a phase advance of 6 hours).advance of 6 hours).

The strong light entrains all The strong light entrains all rhythms not just the sleep rhythms not just the sleep wake cyclewake cycle

Applying this researchApplying this research

Read ‘Reducing the harmful Read ‘Reducing the harmful effects’ section on p9effects’ section on p9

Use this and what you have Use this and what you have learned about the effects learned about the effects

of shiftwork to write a of shiftwork to write a letter or an info sheet for letter or an info sheet for a new company about to a new company about to

employ shift workersemploy shift workers(15-20mins)(15-20mins)

Jet LagJet Lag

Caused by the sudden creation Caused by the sudden creation of a large difference between the of a large difference between the internal clock and the external internal clock and the external worldworld

In the past travel was restricted In the past travel was restricted to short distances.to short distances.

Humans have not evolved a way Humans have not evolved a way of dealing with such sudden of dealing with such sudden disturbancesdisturbances

Our bio-rhythms need 1 day to Our bio-rhythms need 1 day to adjust to each time zone crossedadjust to each time zone crossed

Does the direction of travel make Does the direction of travel make a difference to jet lag?a difference to jet lag?

East to WestEast to WestPhase delayPhase delay. . Easier to cope Easier to cope

with – like going with – like going to bed laterto bed later

Will be ready for Will be ready for bed earlier, but bed earlier, but biological clock biological clock will wake us up will wake us up

earlier tooearlier too

West to EastWest to East

Phase advancePhase advance – – harder – like getting harder – like getting up earlierup earlier

Trying to adjust to a Trying to adjust to a shorter day so shorter day so disruption to circadian disruption to circadian rhythm is more rhythm is more pronouncedpronounced

Daylight, social Daylight, social zeitgebers and clocks zeitgebers and clocks tell us it is morning tell us it is morning when we may still be when we may still be wanting to sleepwanting to sleepRecht et al 1995 – jet lagged baseballers

p8

Commentary on Jet LagCommentary on Jet Lag

Sleep can be disrupted in other ways Sleep can be disrupted in other ways when travelling.when travelling.

Worry about the flight/trip may cause Worry about the flight/trip may cause disrupted sleep the night before a disrupted sleep the night before a journeyjourney

Long trip to get to the airport before Long trip to get to the airport before the holiday startsthe holiday starts

Alcohol and coffee intakeAlcohol and coffee intake Noise, uncomfortable seating, low Noise, uncomfortable seating, low

oxygen in the cabin and annoying oxygen in the cabin and annoying passengerspassengers

Reducing the effects of jet lagReducing the effects of jet lag

Melatonin - Melatonin - ‘Miracle cure’ – ‘Miracle cure’ – Martin 2002 has found that it can Martin 2002 has found that it can help reduce jet lag if it is taken at help reduce jet lag if it is taken at the time of day when the traveller the time of day when the traveller wishes to go to sleep.wishes to go to sleep.

Social customs and meal times Social customs and meal times –– adopt the social rhythms of the adopt the social rhythms of the

destination as social cues destination as social cues help entrain bio-help entrain bio-

rhythms.rhythms.

Reducing the effects of Jet LagReducing the effects of Jet Lag

Stokkan et al 2001 –Stokkan et al 2001 – timing timing of meals can re-set the bio-of meals can re-set the bio-clock in the liver – increases clock in the liver – increases enzyme production at the enzyme production at the right time for digestion right time for digestion avoiding stomach upsetavoiding stomach upset

Bright lightsBright lights – Go out in – Go out in bright daylight on first few bright daylight on first few days in a new time zone to days in a new time zone to reset body clockreset body clock

Explaining shift lag and jet lagExplaining shift lag and jet lag Not well adapted to abrupt shifts in day Not well adapted to abrupt shifts in day

length as length as in nature day length changes in nature day length changes slowlyslowly..

Coren (1996)Coren (1996) – a culture shift happened at – a culture shift happened at the start of the 20the start of the 20thth century when century when electric electric lighting became widely availablelighting became widely available

Factories and offices could Factories and offices could work round the work round the clockclock – introducing – introducing shift work and longer shift work and longer working hours.working hours.

Social activities could also extend later into Social activities could also extend later into the nightthe night

We sleep We sleep 1.5 hrs less1.5 hrs less than 100 years than 100 years ago leading to ago leading to mild sleep deprivationmild sleep deprivation

Explaining shift lag and jet lagExplaining shift lag and jet lag Possible that shift/jet lag causes Possible that shift/jet lag causes

desynchronizationdesynchronization of the body of the body clocks (sleep-wake cycle and core clocks (sleep-wake cycle and core body temperature) leading to body temperature) leading to physical distress.physical distress.

Yamazaki et al (2000)Yamazaki et al (2000) – sleep-wake – sleep-wake cycle can readjust in 48 hours, but cycle can readjust in 48 hours, but other clocks e.g. temperature are other clocks e.g. temperature are slower causing slower causing desynchronizationdesynchronization and the associated symptoms of and the associated symptoms of jet/shift lagjet/shift lag

Takahashi et al (2002)Takahashi et al (2002) – melatonin – melatonin speeded up speeded up resynchronizationresynchronization of of biological rhythms after an 11 hr biological rhythms after an 11 hr flight, reducing jet lag symptomsflight, reducing jet lag symptoms

Evaluation of research on Evaluation of research on disruption of bio-rhythmsdisruption of bio-rhythms

Research findings –Research findings – Consistent evidence to Consistent evidence to show that disruption can have cognitive and show that disruption can have cognitive and emotional effects on people, sometimes emotional effects on people, sometimes leading to drastic consequences, leading to drastic consequences,

but 1000’s of people do shift work without but 1000’s of people do shift work without obvious effects on cognitive ability and obvious effects on cognitive ability and emotional well being (so does it have real-emotional well being (so does it have real-life significance? ).life significance? ).

Methodology Methodology – Evidence often comes from – Evidence often comes from field studies that have high ecological field studies that have high ecological validity,validity,

but confounding variables e.g. personality but confounding variables e.g. personality and individual differences in bio-rhythms are and individual differences in bio-rhythms are not controllednot controlled

Synoptic PointsSynoptic Points

Individual DifferencesIndividual Differences – – Reinberg et al 1984 – found that Reinberg et al 1984 – found that people who gave up shift work people who gave up shift work because they couldn’t cope because they couldn’t cope tended to have rhythms that tended to have rhythms that changed a lot, but ‘happy shift changed a lot, but ‘happy shift workers’ had unchanging workers’ had unchanging rhythmsrhythms

Synoptic PointsSynoptic Points

MethodologyMethodology Lab experiments – Boivin et al 1996 Lab experiments – Boivin et al 1996

(see p9) – effect of light on resetting (see p9) – effect of light on resetting biological clockbiological clock

Good because extraneous variables Good because extraneous variables controlled, controlled, but but low in mundane low in mundane realismrealism

Field expt done (Boivin and James Field expt done (Boivin and James 2002) with nurses using intermittent 2002) with nurses using intermittent bright lights. Findings also showed bright lights. Findings also showed that bright light can reset bio-clockthat bright light can reset bio-clock

This helps to strengthen the previous This helps to strengthen the previous research.research.

Synoptic PointsSynoptic Points ReductionismReductionism Other factors as well as biological Other factors as well as biological

clock disruption must be taken into clock disruption must be taken into considerationconsideration

E.g shift workers being disturbed in the E.g shift workers being disturbed in the dayday

Disrupted social life/social support can Disrupted social life/social support can make people cope with stress less well make people cope with stress less well ((think back to the stress topic – think back to the stress topic – emotion focused copingemotion focused coping) ) Solomon 1993Solomon 1993

Fear of flying, hassle of waiting in Fear of flying, hassle of waiting in airports, caffeine/alcohol intake, airports, caffeine/alcohol intake, discomfort e.t.c may disrupt sleepdiscomfort e.t.c may disrupt sleep

Over to you …Over to you …

Mind map (or summarise in a way that suits you Mind map (or summarise in a way that suits you better) the following …better) the following …

Research into the effects of shift work/jet lag)Research into the effects of shift work/jet lag)( Knuttson et al 1986, Winter et al 2008, Recht et ( Knuttson et al 1986, Winter et al 2008, Recht et

al 1995, Tilley and Wilkinson 1982)al 1995, Tilley and Wilkinson 1982) Research into how shift/jet lag can be minimised Research into how shift/jet lag can be minimised

(Boivin et al 1996 and Boivin and James 2002, (Boivin et al 1996 and Boivin and James 2002, Petrie 2001, , Bambra et al 2008, Gold et al Petrie 2001, , Bambra et al 2008, Gold et al 1992)1992)

Synoptic points – Individual Differences, Synoptic points – Individual Differences, Methodology, ReductionismMethodology, Reductionism

In other words create a plan for an essay on

Disruption of Biorhythms

HomeworkHomework

Discuss the consequences of Discuss the consequences of disrupting biological rhythms.disrupting biological rhythms.

(9+16 marks)(9+16 marks) Look at the sample essay on p 22.Look at the sample essay on p 22. What grade would it get? Use the What grade would it get? Use the

mark scheme on page mark scheme on page vii vii and look at and look at the examiners points.the examiners points.

Now write an essay that is Now write an essay that is better better than the sample!!! than the sample!!!

Use p9 qu 1-4 to help

you

If you fancy more of a challenge try q 5 p9