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The prevention and treatment of
jet lag
It's been ignored, but much can be done
The jet lag syndrome emerged with the rise of long
haul air travel. The symptoms include disturbed sleep, increased
fatigue, loss of concentration, and increased irritability during
the new daytime, and yet difficulties in initiating and maintaining
sleep at night. Long flights are also often tiring and uncomfortable
(travel fatigue), and the dry cabin air contributes to dehydration.
These effects can be distinguished from those of jet lag by comparing
flights across time zones, for example from Europe to Asia, with
flights of similar length along the same meridian, say to southern
Africa, which cause travel fatigue but no jet lag. It is worth trying
to minimise travel fatigue in its own right, and simple practical
advice includes (see box).1
Jet lag is due to the desynchronisation between
various body rhythms and environmental rhythms. The rhythm most
noticeably affected is the cycle of sleep and activity, with the
associated changes in physical and mental functioning. All the rhythms
are regulated by internal and external factors that interact. For
example, the "body clock" controls secretion of melatonin
by the pineal gland, an important internal factor, and light turns
it off. With a rapid change of time zone, it takes several days
for the external factors to shift the phase of the body clock from
the time zone just left to the new zone. Speeding up this adaptive
shift can alleviate or prevent jet lag.
Advice to minimise travel fatigue Before travellingPlan
the journey in advanceTry to arrange for any stopover to be comfortableCheck
documentation, inoculations, visasMake arrangements at the destinationOn
the planeTake some roughage to eat for example, applesDrink plenty
of water or fruit juice (rather than tea and coffee)After arrival
at the destinationRelax with a non-alcoholic drinkTake a showerTake
a brief nap
Non-drug measures maximise the external environmental
cues that push the circadian phase towards the rhythm of light and
dark at the destination. It may be worth trying to start this before
departure. The most important cue is light: after a westward flight,
to stay awake while it is daylight at the destination and to try
to sleep when it gets dark; after an eastward flight, to be awake
but avoid bright light in the morning, and to be outdoors as much
as possible in the afternoon. Such behaviour will adjust the body
clock and turn on the body's own melatonin secretion at the right
time. Other cues can reinforce this eating modestly at the times
that correspond to one's usual mealtimes, taking comfortable exercise,
and seeing favourite sights at times when bright light is advised.
Whether alcohol or caffeine affect adaptation is not clear and probably
depends partly on what a person is used to. They seem more likely
to hinder than to help adaptation and make it harder to assess.
Another option is to use either melatonin or a short acting hypnotic.
Melatonin taken at bedtime both shifts the phase and has a hypnotic
effect, but the relative importance of these two effects has not
been established. A hypnotic treats one symptom by providing sleep,
but it does not shift the circadian phase.
A recent Cochrane review found 10 randomised controlled
trials comparing melatonin with placebo in long distance travellers2;
one of the trials also included a comparison with the hypnotic zolpidem.3
No other randomised controlled trial of a hypnotic for jet lag seems
to have been published. Eight of the 10 trials found a clear reduction
in jet lag when melatonin had been taken. The 10 trials used different
methods to assess jet lag or its components, observations were made
at different times, and most results are reported as group means
without data for individual participants, so that they are difficult
to combine.
For the five studies reporting global jet lag scores
between 0 (none) and 100 (extreme), the mean score after placebo
was 48, after melatonin 25. The two studies reporting individual
results for a total of 46 people suggest that as many as one in
two people using melatonin may benefit. Two trials found no difference:
in one the participants were probably not fully in phase with the
local time before their flight,4 in the other a group of fit sports
scientists and administrators showed only a small effect of uncertain
significance.5 These two trials assessed the different symptoms
of jet lag as well as the rating of "jet lag" itself,
and it might be that not all symptoms change at the same rate and
that the time of assessment might be important jet lag might be
interpreted differently at different times of the day.
Adverse effects have been reported rarely but have not been looked
for systematically. Reports of adverse events possibly related to
use of melatonin imply that two categories of people should avoid
it until more is known: anyone taking warfarin or another oral anticoagulant,
and people with epilepsy.2
The Cochrane review concludes that 2-5 mg melatonin
taken at bedtime after arrival is effective and may be worth repeating
for the next two to four days, together with the non-drug measures
already mentioned. But people who have not had jet lag on a previous
trip may well never need it.
Melatonin (N-acetyl-5-methoxytryptamine) is a simple
substance, but no official standards of purity exist. In many countries
for example, the United States, Thailand, and Singapore it is freely
sold as a "dietary supplement" in health food stores and
pharmacies. Suppliers need present no evidence of the degree of
purity of the melatonin. Four of six melatonin products bought in
health food shops in the United States were found to contain unidentified
impurities.6 It seems advisable to buy it from a large reputable
pharmacy chain and hope for the best. In Europe, Australia, and
many other countries melatonin is regulated as a medicine and requires
a licence, but no licensed preparation is marketed; only the internet
offers a grey or black market.
No pharmaceutical company wants to pay for the toxicological
studies and the data assembly required to obtain a product licence
because it cannot have exclusivity. It seems that many people and
organisations, including governments and armed forces, would benefit
from the use of melatonin to reduce jet lag. If use of the drug
is in the public interest then public funds should be used to get
it properly tested and licensed. A finance initiative is urgently
needed to solve the problem and might best begin with a cost benefit
assessment.
Andrew Herxheimer, emeritus fellow, UK Cochrane
Centre.
9 Park Crescent, London N3 2NL (andrew_herxheimer@compuserve.com)
Jim Waterhouse, senior lecturer.
Research Institute for Sport and Exercise Sciences, John Moores
University, Liverpool L3 2ET
Footnotes
Competing interests: None declared.
1. Waterhouse JM, Minors DS, Waterhouse ME, Reillly
T, Atkinson G, et al. Keeping in time with your body clock. Oxford:
Oxford University Press, 2002.
2. Herxheimer A, Petrie KJ. Melatonin for the prevention
and treatment of jet lag. Cochrane Library 2002; disk issue 4:CD001520.
3. Suhner A, Schlagenhauf P, Hoefer I, Johnson R,
Tschopp A, Steffen R. Efficacy and tolerability of melatonin and
zolpidem for the alleviation of jet-lag. In: Suhner A, ed. Melatonin
and jet-lag. Zurich: Swiss Federal Institute of Technology, 1988:85-103.
(Dissertation ETH No.12823.)
4. Spitzer RL, Terman M, Williams JBW, Terman JS,
Malt UF, Singer F, et al. Jet lag: clinical features, validation
of a new syndrome-specific scale, and lack of response to melatonin
in a randomized double-blind trial. Am J Psychiatry 1999; 156: 1392-1396[Abstract/Free
Full Text].
5. Edwards BJ, Atkinson G, Waterhouse J, Reilly
T, Godfrey R, Budgett R. Use of melatonin in recovery from jet-lag
following an eastward flight across 10 time-zones. Ergonomics 2000;
43: 1501-1513[CrossRef][ISI][Medline].
6. Anon. Melatonin. Med Letter 1995; 37: 111-112.
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