Jet lag is a physiological condition which is a consequence of alterations to the circadian rhythm. Jetlag typically occurs after crossing more than three time zones. Symptoms include insomnia, irritability, and altered bowel habit.
Prevention and recovery from Jet lag
Simple prevention can be good sleep while aboard the plane, and adequate intake of fluids (avoiding caffeine and alcohol) to reduce the effects of dehydration on the body, caused by the dry air at altitude and the interruption of regular eating/drinking patterns.
Drug therapy and light therapy (exposure to sunlight) can help to reset the body's clock.
The condition of jet lag generally lasts many days -- a recovery rate of "one day per time zone crossed " is a fair guideline.
Causes of Jet Lag
When traveling across a number of time zones, the body clock goes out of sync with the destination time, and so it experiences daylight and darkness contrary to the rhythms to which it has grown accustomed. The body's natural pattern therefore becomes upset as the rhythms that dictate times for eating and sleeping no longer correspond to the environment of the destination.
Jet lag occurs because the body cannot automatically realign these rhythms. The speed at which the body readjusts itself to new daylight, darkness hours, and eating and sleeping patterns is entirely dependent upon the individual. Thus, while it may take a few days for some people to readjust to a new time zone, others seem to experience little disruption to their body's natural sleeping pattern.
The symptoms of jet lag can be quite varied, though on the whole, an individual may experience the following:
- Dehydration and loss of appetite
- Headaches and/or sinus irritation
- Disorientation and/or grogginess
- Nausea and/or upset stomach
- Insomnia and/or highly irregular sleep patterns
- Irritability, Irrationality
The condition is not linked to the length of flight, but to the transmeridian (i.e. east-west) distance traveled. Hence a ten-hour flight between Frankfurt and Johannesburg (going south, staying roughly on the same meridian) is less inducive of jet lag than a five-hour flight between New York and Los Angeles (going west).
There seems to be some evidence that traveling west to east is more disruptive, or runs counter to the circadian rhythm. Different individuals may find one adjustment easier than the other. Note that the difference between the two directions decreases as the destination approaches the other side of the Earth (eg from India to USA or UK to New Zealand) which "reverses day and night". While there is a big difference between a -6 and a +6 hours jet lag, there is relatively small difference between -11 and +11 hours.
Treatment for Jet Lag
Melatonin: 5mg of fast-release melatonin (a hormone) can be an effective method to reduce jet lag. It can be used for several days after arrival. While melatonin is available without a prescription in the USA, it is not available in the UK without prescription.
Sedatives: Zolpidem or zopiclone (benzodizepines) may have a better effect on jet lag symptoms than melatonin but have a higher rate of side effects.
A combination of melatonin and a benzodiazepine is a third option.
Sunlight or bright light therapy of 30 mins can help reduce jetlag.
If you travel on an east-bound flight:
- across <6 time zones, light in the morning is advised.
- across 6 to 10 time zones, avoid light in the morning and get light at midday.
If you travel on a west-bound flight:
- across <6 time zones, light in the late afternoon is advised.
- across 6 to 10 time zones, avoid light in the afternoon and get light at midday.