Alterations to the body's circadian rhythms

Alterations to the body's circadian rhythms

Courtesy: Wikipedia Article

 

 

The condition is not linked to the length of flight, but to the trans-meridian (west–east) distance traveled. A ten-hour flight from Europe to southern Africa does not cause jet lag, as travel is primarily north–south. A five-hour flight from the east to the west coast of the United States may well result in jet lag. Crossing the International Date Line does not contribute to jet lag, as the guide for calculating jet lag is the number of time zones crossed, and the maximum possible disruption is plus or minus 12 hours.

 

The common term jet lag is used because before the arrival of passenger jet aircraft, it was generally uncommon to travel far and fast enough to cause jet lag. Propeller flights were slower and of more limited distance than jet flights, and thus did not contribute as widely to the problem.

 

Jet lag is a chronobiological problem, similar to issues often induced by shift work. When traveling across a number of time zones, the body clock will be out of synchronization with the destination time, as it experiences daylight and darkness contrary to the rhythms to which it has grown accustomed. The body's natural pattern is upset, as the rhythms that dictate times for eating, sleeping, hormone regulation and body temperature variations no longer correspond to the environment nor to each other in some cases. To the degree that the body cannot immediately realign these rhythms, it is jet lagged.

The speed at which the body adjusts to the new schedule depends on the individual; some people may require several days to adjust to a new time zone, while others experience little disruption. Crossing one or two time zones does not typically cause jet lag.

 

Jet lag, medically referred to as desynchronosis, is a physiological condition which results from alterations to the body's circadian rhythms resulting from rapid long-distance transmeridian (east–west or west–east) travel on a (typically jet) aircraft. The condition of jet lag may last several days until one is fully adjusted to the new time zone, and a recovery rate of one day per time zone crossed is a suggested guideline.

 

The symptoms of jet lag can be quite varied, depending on the amount of time zone alteration, time of day and the susceptibility of individual differences. Sleep disturbance occurs, with poor sleep upon arrival, sleep disruption including trouble falling asleep (if flying east), early awakening (if flying west) and interrupted sleep with multiple awakenings and trouble remaining asleep. Cognitive effects include poorer performance on mental tasks and concentration, increased fatigue, headaches, and irritability, and problems with digestion including indigestion, changes in the frequency of defecation and consistency of feces and reduced interest in and enjoyment of food. Symptoms are caused by a circadian rhythm that is out of sync with the day-night cycle of the destination.

 

Travel fatigue

Travel fatigue is general fatigue, disorientation and headache caused by a disruption in routine, time spent in a cramped space with little chance to move around, a low-oxygen environment, and dehydration caused by limited food and dry air. It does not necessarily have the shift in circadian rhythms that cause jet lag. Travel fatigue can occur without crossing time zones, and it often disappears after a single day accompanied by a night of high-quality sleep.

 

Management

 

Light is the strongest stimulus for re-aligning a person's sleep-wake schedule and the careful control over exposure and avoidance of bright lights can speed adjustment to a new time zone. Melatonin is used to adjust the circadian clock but there are issues regarding the appropriate dosage and dosage timing, in addition to the legality of the substance in certain countries.

 

North-south flights that do not cross time zones do not cause jet lag. Adjustment to the new time zone is easier for east-to-west travel than west-to-east. A westward adjustment takes, in days, approximately half the number of time zones crossed. For eastward travel, adjusting to the new time zone takes, in days, approximately two-thirds the number of time zones crossed.

 

 

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