Disruption of biological rhythms

Disruption of biological rhythms

Disruptions

•          Where our biological clock has become desynchronised from our external zeitgeber. Physiological cues (e.g. body temp, sleep/wake cycle) desynchronised from external cues (light, meal times).

•          Examples - Jet lag and shift work

Jet lag

•          Plane travel has become common but can be a problem when your biological clock tells you it is one time but local cues tell you it is another.

•          EG: fly to New York from London, leave at midday, takes 7 hours. Arrive 7pm London time which is 2pm NY time. 4 hours later, your body says bed, NY time says party!

•          = JET LAG

Symptoms

•          Tiredness

•          Difficulty with concentration & attention

•          Irritability

•          Anxiety

•          Can last few hours or few days

•          Worse travelling West to East, than East to West. No prob going N to S!

Phase delay

•          East to West travel

•          Our biological clock is ahead of local time and has to ‘wait’ for external cues to catch up.

Phase advance

•          West to East travel

•          Biological clock is behind local time and has to move forward to ‘catch up’.

•          Phase advance seems to be harder to adjust to than phase delay.

How do we get over jet lag?

•          Our SCN (influenced by light entering the eye) needs  to adjust to the changed time in the new place.

•          Can take several days

•          Significant individual differences.

Research

•          Occasional travellers (e.g holiday makers) vs cabin crew studies.

•          Occasional

–        Recht et al (1995), followed baseball team for 3 yrs. They won 37% games when going W to E (phase advance) & 44% when going E to W (phase delay). This was statistically significant

–        But lots of methodological problems (ability of different teams, fluctuations in form, injury). So low validity.

–        Support from American servicemen study – more jet lag when going from Europe to USA (3 days), than USA to Europe (8 days).

Cabin crew studies = Regular exposure

•          Found to have raised levels of stress hormones & do less…