Jet lag
| Jet lag | |
|---|---|
| Specialty | Neurology  |
Jet lag, also jetlag or jet-lag, medically referred to as "desynchronosis" is a physiological condition which is a consequence of alterations to 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 many days, and recovery rates of 1 day per eastward time zone or 1 day per 1.5 westward time zones are mentioned as fair guidelines.[1]
Cause
When traveling across a number of time zones, the body clock will be out of synchronisation 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 (east-west) 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 west to the east 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 twelve hours.
Symptoms
The symptoms of jet lag can be quite varied, depending on the amount of time zone alteration and health of the traveler. They may include the following:[2][3]
- Loss of appetite, nausea, vomiting, digestive problems
- Ear aches, sore throat, swollen feet
- Headache, sinus irritation
- Fatigue, irregular sleep patterns, insomnia
- Disorientation, grogginess, irritability
- Mild depression
Direction of travel
There 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.[4]
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 traveler flying to the East vs a traveler flying to the West:
- Westward from London to Los Angeles, VIA BA0279, Jan 29, 2008. Time zone difference 8 hours.
Westward Biological clock Los Angeles local time Departure JAN 29 - 10:05 JAN 29 - 02:05 Arrival JAN 29 - 21:10 JAN 29 - 13:10 Bedtime JAN 30 - 06:00 JAN 29 - 22:00
- Eastward from Los Angeles to London, VIA BA0278, Jan 29, 2008.
Eastward Biological clock London local time Departure JAN 29 - 15:59 JAN 29 - 23:59 Arrival JAN 30 - 02:05 JAN 30 - 10:05 Bedtime JAN 30 - 14:00 JAN 30 - 22:00
The first scenario is equivalent to staying up all night and going to bed at 6am the next day — 9 hours later than usual. But the second scenario (eastward) is equivalent to staying up all night and going to bed at 2pm the next day — 14 hours after the time one would otherwise have gone to bed.
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]
A recent study in hamsters showed that sildenafil (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.[5] 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 also accelerates recovery rate in both east- and west-travelling hamsters of all ages by 50%; this is thought to be related to simulation of moonlight.[6]
See also
References
- ^ "Sports Medicine Advisor 2005.4: Jet Lag". Retrieved 2009-02-02.
- ^ Cunha, John P.; Stöppler, Melissa Conrad. "Jet Lag".
{{cite journal}}: Cite journal requires|journal=(help)CS1 maint: multiple names: authors list (link) - ^ http://www.jetlagtips.com/Can_jet_lag_cause_you_to_feel_sick_.html
- ^ Rozell, Ned (1995). "Fly East for Bad Jet Lag".
{{cite journal}}: Cite journal requires|journal=(help) - ^ "Viagra could aid jetlag recovery". BBC News. 2007-05-22. Retrieved 2007-05-22.
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