Jet lag - en los viajes largos con cambios de usos horarios

En un viaje de California a Barcelona, el neurobiólogo y especialista en investigaciones del sueño, Lluís De Lecea de la Universidad de Stanford, se aplicó a sí mismo los conocimientos adquiridos en sus estudios, para combatir el jet lag. ¿Conclusión? De todas las medidas para contrarrestar los efectos, la más importante es la exposición a la luz diurna.

El jet lag también conocido como “descompensación horaria”, o “síndrome de los husos horarios”, que ocurre cuando el reloj interno de una persona, que marca los períodos de sueño y vigilia, se desajusta por un largo viaje en avión. Al sufrir el trastorno, se vive con dificultad para conciliar el sueño por la noche y con mucho cansancio durante el día, pero que pueden incluir alteraciones del estado de ánimo, un bajo rendimiento intelectual, una baja forma física y una incapacidad de estar en plenas condiciones.

Si bien cada persona puede experimentarlo de manera muy distinta a los demás, se sabe que cuanto mayor se es, más cuesta adaptarse post viaje. Se puede experimentar jet lag a partir de tres horas de desfase horario pero, cuantas más franjas horarias se cruzan, mayores son los efectos y más días se tarda en sincronizar el reloj interno del organismo.

Las estrategias para contrarrestarlo varían según la dirección del vuelo, advirtió De Lecea. El arsenal de trucos es el mismo: luz diurna, cafeína y actividad física. Pero hay que aplicarlos de manera distinta. Cuando se vuela de Europa hacia América, la sensación que experimenta el viajero es que el día se hace largo.

Por ejemplo, si se viaja de España a Nueva York, cuando aterriza a las dos del mediodía tras nueve horas de vuelo, en su cerebro son ya las ocho de la tarde. En este caso, según De Lecea, para adaptarse a esta situación basta con alargar el día para engañar al cerebro.

Según el especialista, para acertar la receta para ese ejemplo hay que exponerse a la luz solar u otra luz intensa para que el cerebro desista a creer que ya es de noche. También es aconsejable acostarse tarde uno o dos días antes del vuelo para empezar a acostumbrar el organismo al horario del lugar de destino.

Retrasar una o dos horas el horario de las comidas la víspera del vuelo puede ser una ayuda adicional. Y, “en lugar de llegar cansado al avión, cuando se vuela hacia el oeste es mejor llegar descansado para aguantar un día largo”, explicó De Lecea al diario español La Vanguardia. De este modo, uno se podrá ir a dormir cuando ya se haya hecho de noche en la primera noche en América y levantarse fresco al día siguiente.

Por el contrario, cuando uno vuela de América hacia Europa la sensación que experimenta el viajero es que le “hurtaron” una noche. Cuando aterriza, por ejemplo en Barcelona, a las ocho de la mañana procedente de Nueva York, en su cerebro son aún las dos de la madrugada. En este caso, ya no basta con engañar al cerebro alargando el día, hay que convencerlo de que empezó un nuevo día.

Para conseguirlo, conviene exponerse a la luz diurna a lo largo de la mañana para convencer al cerebro de que ya es de día y evitarla por la tarde.

“La luz solar es el instrumento natural más eficaz para regular el ciclo de sueño y vigilia”, destaca la Clínica Mayo de EE.UU. en un documento dedicado el jet lag. La razón está en el núcleo supraquiasmático del hipotálamo (NSH), que es el reloj que fija el horario de todo el organismo.

De Lecea dice que para “el viajero ocasional, no soy partidario de tratarlo con somníferos o medicación”. “Me parece mejor aprender cómo funciona nuestro cuerpo y aplicar tratamientos naturales eficaces basados en la exposición a la luz y en adaptar nuestro reloj interno al horario del lugar de destino”, concluyó.

(Fuente: La Vanguardia)

Jet lag, medically referred to as desynchronosis, is a physiological condition which results from alterations to the body's circadian rhythms; it is classified as one of the circadian rhythm sleep disorders. Jet lag results from rapid long-distance transmeridian (east–west or west–east) travel, as on a jet plane.

The condition of jet lag may last several days, and a recovery rate of one day per time zone crossed is a fair guideline

Cause
Jet lag is a chronobiological-related problem[2], 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.

The condition is not linked to the length of flight, but to the transmeridian (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. If the time difference between two locations is greater than 12 hours, subtract that number from 24. Note, for example, that the time zone GMT+14 will be at the same time of day as GMT−10, though the former is one day ahead of the latter.

Symptoms
The symptoms of jet lag can be quite varied, depending on the amount of time zone alteration, time of day and individual differences. They may include the following:[3]

Headaches
Fatigue, irregular sleep patterns, insomnia
Disorientation, grogginess, irritability
Mild depression
Constipation or diarrhea
Jet lag has been measured with simple analogue scales but a study has shown that these are relatively blunt for assessing all the problems associated with jet lag. The Liverpool Jet lag Questionnaire was developed to measure all the different symptoms of jet lag at several times of day, and this dedicated measurement tool has been used to assess jet lag in athletes.Waterhous et al., 2002

Management
It is possible to minimize the effects of jet lag by following some basic steps before, during, and after the flight. Full details of these steps can be found in two reviews published in the Lancet[4]. There is also a position statement from the European College of Sports Science for management of jet lag in athletes[5].

Before the flightIt is recommended to visit the doctor to plan a coping strategy for medical conditions that require monitoring, including when to take medications or any other necessary detail.

One tactic is to attempt to partially adapt to the destination time zone in advance. This includes starting the daily routine one hour before or after one normally does during the week before departure. The use of a light box might help speed up the body's body clock adjustment significantly.[6]

During the flightTo avoid dehydration, passengers are discouraged from taking alcoholic beverages and caffeine, as caffeine disrupts sleeping schedules. It is recommended to drink plenty of water to help counteract the effects of the dry atmosphere inside the plane.

One option to counteract jet lag is to break the trip into smaller segments if it is too long and stay overnight in some city. Additionally, it may be advisable to adjust sleeping hours on the plane to match the destination time.

Upon arrival
A helpful way to minimize jet lag is to adapt to the local time and eat accordingly. Also, exposure to sunlight during the day is helpful.[7]

Direction of travelThere seems to be some evidence that for most people, traveling west to east is more disruptive. This may be because most people have a circadian period which is a bit longer than 24 hours, making it easier to stay up later than to get up earlier, also traveling west is the opposite direction of the Earth's rotation.[8]

It may also be that flights to the east are more likely to require people to stay awake more than one full night in order to adjust to the local time zone. For example, comparing a typical schedule for a traveller flying to the west vs a traveller flying to the east:

Westbound from London to Los Angeles. Time zone difference: 8 hours.
The first scenario is equivalent to staying up all night and going to bed at 6 a.m. the next day—8 hours later than usual. But the second scenario (eastward) is equivalent to staying up all night and going to bed at 2 p.m. the next day—14 hours after the time one would otherwise have gone to bed. Some sleep onboard may help the situation somewhat.

The red-eye flight is another eastward scenario, for example flights departing the west coast of the US at midnight (PST/PDT) and arriving on the east coast early in the morning (EST/EDT). Relative to the shorter flight time and the time zones advanced, the body gets less than optimal rest to begin a day of activity.

Remedies
Since the experience of jet lag varies among individuals, it is difficult to assess the efficacy of any single remedy. Gradual adjustment over the course of several days of the onset of sleep while maintaining its regular length of 7–8 hours can reduce fatigue and prevent depression. When the goal is to catch-up with local time (vs. fallback to), this can be aided by avoiding afternoon naps and eating an early and carbohydrates-rich, low-protein dinner.[citation needed]

Most chemical and herbal remedies, including the hormone melatonin, have not been tested nor approved by official agencies such as the United States Food and Drug Administration. Few studies have tested the use of melatonin for jet lag and have given mixed results, likely because the timing of administration needs to be precise and individualized.[citation needed]

Melatonin
Melatonin is present in the bloodstream naturally in differing amounts according to the time of day. It is produced by the pineal gland in darkness; secretion stops when there is light to the eyes. It plays a key role in the circadian rhythm which regulates various significant body functions.[9]

A 2005 study showed that melatonin was effective in helping people fall asleep at doses of 0.3 milligrams (mg). Then, to treat the jet lag, the recommended dose of melatonin is 0.3–0.5 mg, to be taken the first day of traveling. Administration of higher doses can cause sleepiness, lethargy, confusion, and decreased mental sharpness.[7]

A position statement on the use of melatonin for alleviating jet lag in athletes was published in the British Journal of Sports Medicine[10]. Melatonin is not recommended for people with the symptoms of severe mental illness, severe allergies, autoimmune diseases, immune system cancers, or pregnant women.[11]

Light therapyThe body requires approximately one day per time zone to adjust its circadian rhythm. A manufacturer of light-therapy lamps claims that using light therapy can speed this process up to one hour per time zone when used at the correct time, combined with avoiding light during specific periods.[12]

Animal studies
A recent study in hamsters showed that sildenafil citrate (known commercially as Viagra) aided in a 50% faster recovery from shifts comparable to eastward travel experienced by humans and was effective starting at low doses.[13] However, this use has not been tested in humans and is considered an off-label use by the drug's manufacturers.

The presence of low-level light at night accelerates recovery rates in both east- and west-travelling hamsters of all ages by 50%; this is thought to be related to simulation of moonlight
 Wikipedia source.