6.6.1.  JET LAG SYNDROME

6.6.1.1. MANIFESTATIONS

– High fatigue.

– Alertness, mood and performance disorders.

– Disturbed sleep. 

6.6.1.2.  SHIFTING ENVIRONMENTAL SYNCHRONIZERS

Free running is the natural tendency for 24-hour cycles to extend in the absence of external time-givers. This is why it is easier to delay bedtimes and rising times than to advance them.
 
 
6.6.1.2.1.  Westward flights 

Delay of environmental synchronizers phase: dark-light alternation, rest-activity cycles, social rhythms, etc.
Synchronization to the new time requires going to bed and getting up at increasingly later times.
 

local-time Issues and h

6.6.1.3. SCHEMATIZATION OF PSYCHO-PHYSIOLOGICAL ADJUSTMENT STEPS

6.6.1.3.1. Example: Westward flights 

At 1 to 2 days after the flight, the circadian system and environmental synchronizers are out of phase.
Under normal conditions, the biological clock is in phase with the environmental synchronizers: the period of least efficiency (OFF) coincides with the nocturnal period, the period of maximum efficiency (ON) with the diurnal period.
Due to its inertia, the biological clock does not immediately adjust to the new time zone after having crossed several ones. The result is a sudden shift between local time in the country of arrival and the biological body clock, which is still synchronized with home time.
 

 
At 3 to 4 days after flight: internal dissociation.
 
Progressive adjustment (by phase delay) of bedtimes and rising times and of psycho-physiological functions.
 
Adjustment rate: 1 to 1.5 hours per day.
 
The psycho-physiological functions adjust at various speeds: 1 week for temperature, 3 weeks for endocrine rhythms.
 
The result is a loss of harmony in the circadian system called "internal dissociation" and responsible for the jet-lag syndrome.
 
 

 
 
At 8 to 9 days after the flight: adjustment of the circadian system.
 
Synchronization between local time and biological time.
 
Synchronization between most parts of the psycho-physiological functions.
 
 

 
 
6.6.1.4. LAYOVER & RETURN TO BASE 

If layover time is short (< 48 hours), it is preferable not to adjust but to continue living according to home or base time.
 
The longer the layover, the more the body will adjust to the new time zone and the more difficult it will be to synchronize with home or base time after the return flight.
 
The rest period after the return flight to home or base must be at least equal to the previous layover period to allow for resynchronization.
　
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