Air Travel and Health: Summary of a Conference

• Taking aspirin in conjunction with air travel to prevent deep vein thrombosis (DVTs) may or may not decrease the incidence of DVTs but probably increases bleeding episodes.

• Air travel is the safest form of mass transportation and is becoming safer. The next step in reducing mishaps is to study the health and cultural issues of the flight crew.

• Benzodiazepines are widely used in the treatment of phobias and may be particularly helpful in short-term use as an aid to overcoming flight anxiety.

This is a mere sampling of the thought-provoking material (see below for details about these and more), presented at the First International Conference on Air Travel and Health held in Eilat, Israel in November. About two dozen experts in travel and aviation medicine from 10 countries held 28 sessions covering virtually every aspect of the subject, with much time spent on DVTs, the current "hot issue" in the field.

The meeting was organized and chaired by Benjamin Brenner and Israel Potasman, and was sponsored/organized under the auspices of a number of organizations including the ISTM and the Aerospace Medical Association. Israel (the person, not the country) is an active member of ISTM.

The meeting venue, Eilat, is a tropical resort known for its warm weather, little rain, and water sports. It is situated at the southern tip of Israel on the Red Sea, (which, in fact, is deep blue in color and exceptionally clear.) Four countries abut here. The city of Acaba, Jordan is next door, the border of Egypt is 200 meters down the road from the convention hotel, and Saudi Arabia is easily visible across a narrow bay.

Clearly air travel continues to grow. The number of passengers flown each year worldwide will soon pass the 2 billion mark, bringing to the forefront many health issues. Flights of 15 hours or more are becoming commonplace, and aircraft are becoming larger. What used to be called "jumbo jets" will soon be dwarfed by the Airbus A380, which, coincidentally, was going through some of its final test flights at the time of the Conference and is expected to receive its airworthiness certification in the next few months. The first commercial A380 flight is scheduled for late 2007. The A380 will have a capacity of more than 700 passengers on two decks. Still being debated is whether the aircraft will have a medical facility on board and, if so, the type of facility and who will staff it, said Michael Bagshaw, one of the speakers and a consultant to the company building the aircraft. Michael is a physician, an aerospace medicine specialist, a teacher of physics at the college level, and a former captain for British Airways flying large jets. (He is also a musicologist and a singer.)

(However, even an A380Airbus filled to capacity will probably not hold the record for the largest number of passengers on any one flight. On May 24, 1991, in "Operation Solomon," an El Al Israel Boeing 747 transported 1087 individuals, almost all of them Ethiopian Jews, to Israel, said several speakers involved in the mission. The only medical event of note was that the aircraft arrived in Israel with one more individual than left Ethiopia: an infant was born during the flight, a miracle in the eyes of some. Also, in spite of the high incidence of tuberculosis among the Ethiopians and the severe crowding on the aircraft, in follow-up studies, no case of tuberculosis was detected in the dozens of Israelis among the flight crew and accompanying personnel.)

The introductory lecture at the conference was about air travel of a different type: bird migration. Because of its location at the juncture of three continents (Asia, Europe, and Africa), Israel lies in the pathway of numerous routes of migratory birds. In fact, according to the speaker (who was extremely interesting and humorous), Israel, per square kilometer, has more types and numbers of migratory birds stopping over than any other country. This makes Israel a "paradise" for bird watchers, but not for aviation, making bird watching an important endeavor, not merely a hobby. A better understanding of migratory routes for each type of bird, the times of the year birds fly, and where they decide to rest, may help aviation authorities to warn pilots about bird hazards. Several Israeli aviation mishaps have been blamed on birds.

Here is some of the other material presented by the speakers, all experts in their fields. Please note that the opinions expressed in this article are those of the lecturers.

• Infants. There are no known reasons for airlines to have lower age limits for allowing healthy infants to travel by air. Such limits vary from none to four weeks. There are no reports in the medical literature of a healthy infant having a health problem as a result of flying. And none of hundreds of travel and aviation medicine experts, including many medical directors of major airlines, queried at various conferences, is aware of a case.

  However, theoretically and based on studies done in non-aviation settings, infants who were born prematurely and infants who had significant neonatal pulmonary problems may be at risk in flight. Such infants, even those who are asymptomatic at home, may desaturate at the atmospheric pressures present in aircraft cabins at cruising altitudes, and may require supplementary oxygen. Whenever possible, such infants should not travel by air until they are 12 months of age.

• Outbreaks of gastrointestinal diseases during flight. Forty-one incidences of gastrointestinal diseases, with ten deaths, were reported before the year 2000 and none has been reported since, even though the number of flights and the number of passengers has increased significantly. The likely reason is better sanitation and more scrutiny. (Drinking water is now served from sealed bottles rather than from large jugs, for example.) However, many cases of intestinal illness occurring in flight may go unreported. Flights tend to be relatively short compared with the incubation period of common infectious intestinal disorders.

  Of the known outbreaks of gastrointestinal disease, many more occurred among first class passengers than economy passengers. First class passengers are served fancier foods, ones that require more handling in preparation and are more likely to become contaminated, fancy small sandwiches, for example.

  Many airlines recommend that their captains and co-captains eat food prepared in different catering kitchens to prevent both from being incapacitated at the same time should a virulent outbreak occur. However, in practice, the entire crew eats the same meals. Economics have forced most airlines to buy all food from a single caterer.

• Cosmic radiation. All possible precautions should be taken to minimize passengers' and air crew's exposure to cosmic radiation, including expensive (for the airlines) diversion during periods of increased solar activity. Such activity tends to be most common on routes over the extreme northern part of the North Atlantic in wintertime.

  However, present data suggests that the amount of radiation that passengers, even frequent flyers, are likely to receive is insufficient to cause problems. And, even flight crew seem to be at low risk. Nevertheless, many governments are studying the issue, and some have declared that being a member of an air crew is a hazardous occupation. Some studies have found an increase in the incidence of melanoma among air crew and an increase in the incidence of breast cancer in female air crew. However, life styles and other conditions specific to air crew may be responsible for these increases.

• Melatonin and jetlag. Melatonin is frequently used by air travelers, and sometimes by air crew because it helps induce sleep and enhances resynchronization of the circadian clock. There are no known significant side effects or impaired psychomotor or cognitive functioning associated with melatonin. However, melatonin potentiates the adverse effects of zolpidem (Ambien) and, perhaps other hypnotics, and possibly alcohol. Because of these and other considerations, melatonin is not available in some countries.

• Fear of flying. Flight anxiety is a fairly common phobia, characterized by an excessive and irrational fear of flying. Effective treatments include various psychological and pharmacological approaches. Benzodiazepines are widely used in the treatment of phobias and are particularly helpful in short-term use as an aid to overcome flight anxiety. They can be started a few days before a planned flight to reduce anticipatory anxiety, and then taken aboard to reduce in-flight anxiety and reduce the risk of a panic attack. Long-term use is not recommended, as it carries the risk of habituation, dependence, and withdrawal-related problems. SSRIs (Selective serotonin re-uptake inhibitors) seem to be an excellent alternative; however these drugs need to be started about one month before the flight.

  The worst time for flight for phobic passengers is when the doors close at the onset of the flight and while the aircraft taxis on the ground after landing, until the doors open and they can deplane.

• Deep Vein Thrombosis. The number of studies linking deep vein thrombosis and air travel is rapidly increasing, but the causative mechanism remains allusive. The vast majority of travelers who experience DVTs have well known risk factors for DVTs, and most are on long flights. Asymptomatic clots occur very frequently, as is shown by radiological studies. Lesser-known risk factors include women for several weeks after giving birth and short stature individuals. (The legs of short individuals do not reach the floor during sitting.)

  Controversy remains regarding preventative actions. Aspirin, to be effective, must be started several days before flights, and may increase bleeding tendencies. (A show of hands revealed that some attendees admitted to taking aspirin for air travel.) Elastic compression stockings, in order to be effective, must fit well and must apply the correct pressure. Low molecular weight heparin may be effective but the safety ratio (bleeding events) is not known. An intermittent mechanical compression device for the legs is now being studied.

• In-flight headaches. Almost 6% of air travelers experience severe headaches, some travelers on every flight that they take. Headaches most commonly occur during ascent and descent. Air travelers especially at risk are females and individuals with a history of severe migraine headaches. Migraine sufferers seem to experience more severe headaches during flight than at other times.

• Air travel safety. Accidents due to mechanical failure of the aircraft are decreasing more rapidly than accidents traced to human factors. Human factors that contribute to accidents are health of the air crew, especially mental health and cultural issues. Many experts believe that several crashes in aviation history were due to pilots committing suicide. Other accidents can be traced to first officers not intervening promptly when captains were operating the aircraft inappropriately. In some of these situations, the first officers' failure to intervene may have been influenced by cultural traditions that strongly disapprove of challenging superior authority.

Karl is the editor of NewsShare.