Jet lag perils probed

By Susan Okie Washington Post, 5/23/2001

Almost anyone who has flown across several time zones has experienced jet lag - the fatigue, mental fogginess, and vague discomfort felt by travelers whose body clocks are out of sync with their environment.

But for some long-distance fliers, jet lag might be more than just a temporary annoyance. A study of 20 flight attendants suggests that people who undergo repeated, frequent episodes of jet lag may develop impairment of visual memory and may even suffer some shrinkage of an important part of the brain.

If the findings are confirmed, they could have implications for airline employees and frequent travelers as well as shift workers, medical trainees, and others who work long hours.

''The 8 million people who regularly work at night in this country may be experiencing some of the same phenomena,'' said Charles A. Czeisler, a professor of medicine at Harvard Medical School.

The research involved brain-imaging and memory tests on flight attendants who regularly traversed at least seven time zones.

So far, the data reveal that frequent jet lag without sufficient recovery time affects the brain's structure and function, said Kwangwook Cho, a neurologist at the University of Bristol, England, who performed the study, which appears in the June issue of the journal Nature Neuroscience.

Cho is ''finding actual tissue changes in the brain in an area that's involved in spatial orientation and related aspects of cognitive function,'' said Thomas Wehr, chief of the section on biological rhythms at the National Institute of Mental Health. More research is needed, he said, to determine whether the changes are related to sleep deprivation, jet lag, or both.

For the study, Cho recruited 20 healthy female flight attendants who worked for various airlines and had held their jobs for several years. All made regular flights across at least seven time zones, but half the women (the ''short-recovery group'') spent five days or fewer in their home time zone between long trips, while half (the ''long-recovery group'') spent more than 14 days in the home time zone, working on shorter flights during that period. The number of hours spent on and off duty was comparable between the two groups.

For each participant, Cho took saliva samples to measure levels of cortisol, a hormone whose levels rise during times of stress. He also used magnetic resonance imaging to measure the size of the temporal lobes, areas of the brain involved in language, memory, and emotion. And he evaluated visual memory with a test that required participants to recall the location of black spots flashed on a computer screen.

In the flight attendants in the short-recovery group, the size of the right temporal lobe - a brain region key to visual and spatial memory - was slightly but significantly smaller than in the long-recovery group. The short-recovery group also performed more poorly and had slower reaction times on the visual memory test. Although cortisol levels were not significantly different between the groups, higher levels tended to correlate with smaller temporal lobe sizes in the short-recovery group.

''After they have more than four years in service, most cabin crew told me ... they notice their memory is getting worse,'' Cho said. ''Clearly, we can prevent that kind of side effect simply by changing the schedule.''

This story ran on page 23 of the Boston Globe on 5/23/2001.
 

For more on this story

Reuters contributed to this report.

Flight Attendants Survey on Jet Lag and No-Jet-Lag**
** When referencing this study give credit to www.nojetlag.com
 

A survey was carried out in 1994 among New Zealand based flight attendants regularly flying routes to Asia, the United States and Europe, with the assistance of their union - F.A.R.S.A. They were asked how many suffered from jet lag, what symptoms they suffered, and whether No-Jet-Lag was effective in countering them.

A total of 228 flight attendants completed survey forms, giving the following responses:

Have you suffered from jet lag while travelling on long distance flights?
Answer = 96% said yes, 4% said no.

Specifically have you suffered from

Tiredness over the first five days after arrival = 90% yes
Disorientation = 53% yes
Dehydration = 73% yes
Lack of energy and motivation = 94% yes
Swelling of limbs = 32% yes
Broken sleep after arrival = 93% yes
Ear, nose, throat problems, colds or flu = 70% yes
 

How effective was No-Jet-Lag in countering jet lag symptoms for you?

Very good = 32%
Good = 43%
Fair = 23%
Made no real difference = 2%
 

Did you find No-Jet-Lag effective in countering tiredness after arrival?

Yes = 87%, No = 13%

Note; A US based survey found that 94% of long distance travellers suffered from the effects of jet lag and that 45% considered those symptoms severely bothersome.

A survey was carried out among New Zealand-based flight attendants regularly flying international passenger routes to Asia, the United States and Europe, to determine how many suffered from jet lag and what symptoms they experienced. The survey was conducted with a view to identifying the symptoms that might most appropriately be targeted by a preparation designed to alleviate jet lag among flight crew.

The survey was carried out by Miers Laboratories, a New Zealand company which designs and markets homeopathic preparations. The questionnaire also invited respondents to comment on the efficacy of a preparation designed to counter jet lag. (This was not a formal trial; results of an independent controlled trial are currently in preparation for publication.)

Jet lag is widely considered to be a curse of modern jet travel, resulting in loss of working efficiency and holiday enjoyment, often for days after arrival at destination.

A number of studies have shown that over 90% of long distance travelers suffer from the effects of jet lag. A major US study of long distance travelers with United Airlines and British Airways found that 94% suffered jet-lag symptoms, and 45% considered their symptoms severely bothersome (2).

An objective of our survey was to ascertain whether airline personnel, who might be expected to have developed an "immunity" to jet lag and to be aware of practical methods to counter some of its effects, suffered the same symptoms as passengers.

Jet lag is typically characterized by a number of well-known symptoms easily recognized by the sufferer. They include:

Disruption to circadian rhythms caused by crossing time zones, which can result in broken sleep, with the sufferer waking during the night and then wanting to fall asleep during the day. The number of days this dysrhythmia lasts has been observed to be about equal to the number of time zones crossed. A study by Air New Zealand states that passengers crossing 12 times zones on a 26-hour flight require ten days to re-establish a normal sleep pattern (1).

Fatigue, lasting for days after arrival. This is often accompanied by a lack of concentration and motivation, especially for any activity that requires effort or skill, such as driving, concentrated reading or business negotiation.

Disorientation and vagueness. Respondents in our survey mentioned, for example, having to return to their hotel room three times to check if they had left the door locked.

In addition to the above symptoms of jet lag proper, the syndrome is made worse by the physical effects of being confined in an airliner for hours:

Discomfort of legs and feet due to limbs swelling while flying, which in some cases can prevent travellers wearing their normal shoes for up to 24 hours after arrival.

Dehydration due to the dry atmosphere aboard airliners, which can cause headaches, dry skin and nasal irritation. This in turn can result in a general feeling of unwellness and make the subject more susceptible to colds or other infections.

The World Health Organization also cites jet lag as an aggravating factor in cases of diarrhoea caused by microbiological contamination of water or food, which it believes affects between 20% and 50% of travellers (3).

Since the biggest single cause of jet lag is crossing time zones, which disrupts the body's circadian rhythms, the syndrome is most severely felt when associated with east-west, west-east or transpolar flights. The effects are made worse by variations in atmospheric pressure each time the aircraft takes off and lands, and also by pre-flight stress, tiredness or hangovers. Other factors that appear to exacerbate jet lag include the dryness of the air supply aboard passenger aircraft, the temptation to consume alcohol and to eat more than necessary during flight, and the lack of body movement, especially in the legs and feet.

In our survey of New Zealand-based flight attendants rostered on inter-continental flights, a questionnaire was sent to all long-haul members of their union, the Flight Attendants and Related Services Association, with an explanation of the purposes for which the research was being carried out. Participation was voluntary, and 228 forms were returned. The union facilitated the survey and encouraged members to participate but did not attempt to influence the responses, which were mailed direct to Miers Laboratories for analysis.

In response to the first question, "Have you suffered from jet lag while traveling on long distance flights?" a high 96% said "yes", a result which is in line with responses in surveys of long-haul passengers. This would tend to indicate that being regularly exposed to and trained to cope with the strains of long-haul air travel does not diminish the likelihood of experiencing jet lag. However, the survey did not attempt to quantify the severity of the symptoms of flight crew as compared with passengers.

Flight attendants were then asked whether they commonly experienced specific symptoms of jet lag during and after long-haul flights. Their responses were as follows:

Tiredness over the first five days after arrival, 90%.
Interrupted sleep after arrival, 93%.
Lack of energy and motivation, 94%.
Disorientation, 53%.
Dehydration, 73%.
Swelling of limbs, 32%.
Ear, nose, throat problems, colds or flu, 70%.
 

Circadian dysrhythmia is thus experienced by about the same proportion of flying professionals as of passengers. This appears to contradict the often heard claim that frequent travelers develop an ability to overcome this problem.

Another noteworthy finding was that a very high 73% of flight attendants experienced dehydration. Dehydration in flight can be largely countered by regular drinking of water (as distinct from alcohol, coffee, fruit juice, etc), and it appears the flight attendants had either not been told of this in training or were not following recommended practice.

Also surprising was that 32% of flight attendants experienced swelling of limbs, a symptom generally attributed to passenger immobility during long flights. This may indicate that other factors such as changes in air pressure or dehydration contribute to limb swelling.

In answer to the question "how effective was the homeopathic preparation, No-Jet-Lag in countering jet lag symptoms," 75% of the 55 flight attendants who used No-Jet-Lag said it was either good or very good in countering jet lag symptoms.

REFERENCES

1. Petrie K, Conaglen JV, Thompson L, Chamberlain K. Effect of melatonin on jet lag after long haul flights. British Medical Journal 1989; 298:705-707.

2. The Upjohn Company. Tips for Overcoming Jet Lag (leaflet). Kalamazoo, mi: The Upjohn Co., nd.

3. WHO, Geneva. Safe Food for Travellers: WHO's Recommendations (leaflet). 28 June 1994.

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