Purdue University, English 105
Dr. Bolduc, Fall 1988
Grade: (A)
Jet Lag: The Effects on Health
The entire universe operates via cyclic or rhythmic processes; from the galaxies rotating around their centers to the microscopic world of the atom. The cycle of day and night which lasts for 24 hours is caused by the earth's rotation around it's axis; the specific distance from the sun affects the amount of light and the amount of warmth present. The nucleus of an atom has electrons revolving around it which controls its cyclic processes.
Man is also cyclic, his body clock, or his physiological clock functions to tell him when to eat, sleep, be active or when to play. Man's rhythm is circadian. Circadian comes from the Latin word, circum which means "about", and dies which means "day." This biorhythm involves a period of 24 hours; also called the circadian cycle; this cycle controls our levels of wakefulness and sleep. "The cells of our bodies contain timers or "individual clocks" which in association with RNA (ribonucleic acid) process proteins in a cyclic 24-hour period." 1
So our actual chemical makeup contains our clock. The clock receives cues from several sources called Zeitgebers (German word which means "time giver"). Some of these cues are external and some are internal. Light is an important zeitgeber in controlling our circadian rhythm; lighting cycles regulate endocrine function in our bodies. Our endocrine glands control the production of hormones such as adrenaline, cortisone, and thyroxin which all play a role in regulating our circadian rhythm; cortisol levels are high early in the am and low in late evening; cortisol levels rise to their highest an hour before the person awakes in the morning.
Neuroanatomists are now aware of a pathway from the eye to a spot in the hypothalamus called the suprachiasmatic nuclei which allows light to have an internal effect on synchronization of our rhythm. These nuclei seem to be in control of our rhythms. Research has shown that if the connection between the retina and the suprachiasmatic nuclei is damaged, light can no longer reset the biological clock, in spite of the fact that the person can still see.
The pineal gland is also known to function in controlling our clock; in humans, it secretes large amounts of melatonin in young children; the greatest amounts are secreted at night during sleep. The level of melatonin declines towards puberty; melatonin also makes people sleepy; children with large amounts thus sleep more than adults. Studies with sparrows have shown that you can exchange a jet-lagged sparrow's pineal gland with one from the new time zone and cure his jet lag. Removing the pineal gland in rodents allows the suprachiasmatic nuclei to rapidly adjust to a time zone change. The pineal gland is suppressed by some drugs used to treat mental illness; a widely used antidepressant has been found to reset biological rhythms in rodents.
An internal zeitgeber is temperature; ordinarily our body temperature (inside or core temperature, not on the skin) rises at midday to 37 degrees centigrade and falls at night to 36 degrees centigrade. The temperature curve is an easily measurable indicator of our biological clock. The electrical activity of the brain shows distinct stages in the sleep-wakefulness cycles that can be measured via an electroencephalograph or EEG.
The urinary system does most of its work during the day, the purpose being to allow undisturbed sleep; studies have shown that the by-products of the hormones that control circadian rhythms can be found at corresponding appropriate times in the urine. Studies have shown that midday corresponds with the time that people are found to have the best ability to perform complex tasks; this correlates with the fact that most people like to be awake during the day.
Light and temperature act as cues to control our circadian rhythm, yet studies have shown that there are existent circadian rhythms even under experimental conditions with constant light and temperature; these are called free-running rhythms. Without light-dark cues the circadian cycle is said to be running in a free-running manner; it is following the natural internal timing of the body. "Sleep experiments have proved, however, that humans are capable of adapting to a slightly shorter or a slightly longer day." 2
We rarely exceed twenty to twenty-eight hours and are usually within an hour or two of twenty-four hours. Experiments attempting to change the circadian rhythm were unsuccessful. Young people placed in a cave-like environment with only artificial light agreed to go to bed when the clock said 11:45 PM and to get up when it said 7:45 AM. Though they did not know it the clock began normally, but then gradually went faster till the day reached twenty-two hours. At the time the clock was at the twenty-three hour part none of the participants had any trouble, but when it reached twenty-two hours only one person was able to keep up with the clock.
After babies are born from a lightless uterus they exhibit many alterations in their sleep/wake cycle during the first two to three months; the cue that tells them when to wake up is their hunger; the contractions of the stomach wake them up. It takes about three months for babies to develop enough to become curious about seeing the world and thus gradually become more light active. By nine months their body clocks are like that of adults.
Jet lag is a disruption in this rhythm caused by traveling across a number of time zones; the traveler's entire body functions are out of sync with those of the people at his destination. When we cross more than four time zones we exceed our clock's ability to reset itself. The symptoms of jet lag are many: sleepiness, headaches, alertness, and being hungry at times that are inappropriate. Intellectual functioning is affected; it is hard to learn new things, hard to concentrate, and hard to understand things when experiencing jet lag. Other symptoms are anxiety, nervousness, irritability, anger, depression, and inappropriate euphoria or depression. Usually, the return of intellectual and emotional functioning occurs in three to four days. It may take a week for sleep, appetite, and energy levels to return to normal; levels of serum electrolytes (sodium, potassium, and chloride) may take a few days longer; it may take two months for hormone functioning to return to pre-trip normals.
Examples of geographic time zones crossed are: coast to coast in the United States is four time zones, California to Scandinavia covers twelve, and from New York to New Delhi leads to a complete inversion of the sleep/wake cycle. This desynchronization causes a phase shift between the physiologic and the geographic cycle. Flying east causes things to advance and going west causes a delay in the day/night cycle. " Most travelers adjust to a new circadian cycle at the rate of one hour per day." 3
The older we get the more sensitive we are to jet lag. There are very few people who are not affected much by jet lag. Some find it easier to adjust to eastbound, some to westbound flights; some say that it is easier to adjust on home turf because of the familiar surroundings. " It turns out that your body cannot adjust to changing time zones much faster than two hours a day, as though your skin can travel at arbitrary speed but your insides are limited to about 100 miles an hour." 4
An exhaustive study was done by Wegmann et al. in association with Stanford University School of Medicine and NASA (U.S. National Aeronautics and Space Administration) using B-747 aircrews operating regular passenger flights between Frankfort and the U.S. West Coast. The main purpose was to study sleep in aircrews exposed to time zone changes. They knew that multiple time zone transitions caused disruption in the circadian rhythm; their goal was to define changes in the twenty-four-hour fluctuations of selected variables. They studied sleep EEG and daytime sleep latency in the laboratory; they continuously recorded body temperature, EEG, and took frequent urine specimens. Additional measurements were conducted during pre-duty, during flight, and during layover. In order to also check readjustment at home, the study continued for two days at home.
The design of the experiment was initiated because of their hypothesis: due to considerable time zone changes in the routes of the aircrews they would experience disruption of their circadian rhythms; they would then show sleep difficulties. According to their sleep log analysis, the surveys do not support the above hypothesis. The study showed that the pilots sleep much more on layover and did not suffer from sleep loss when compared to their sleep at home. Results showed that time-zone transition did desynchronize their circadian rhythm, but with naps and staying awake for periods, and then sleeping long periods they were able to cope with the disruption. From personal conversations with the pilots, they found that they were very much aware of the potential difficulties and took serious measures to obtain enough sleep; the studies show that they are indeed successful. The study did find a difference with age; older pilots had to stay in bed longer to get enough sleep.
Another study was done by NASA in conjunction with an international research team; British, German, Japanese, and U.S. research teams each associated with an international carrier along with support in their own country. The goal of this layover sleep study was the assessment of sleep changes encountered with multiple time zone changes; how does sleep differ at home when compared to sleep during a trip; the subjects were long-haul flight crews. After baseline sleep EEG recordings, the crews underwent testing during nocturnal sleep followed by multiple sleep latency tests every two hours whenever they were awake and not trying to sleep; this provided objective information about the quality, and quantity of daytime sleepiness for comparison with the subjects' own estimates.
The sleep recordings included EEG, electromyographic or EMG, and electro-oculographic or EOG activity. (EEG involves brain waves, EMG involves muscle activity and EOG records eye movements). Before each sleep recording the pilots completed a Stanford Sleepiness Scale or SSS, a mood assessment scale, and a self-report to check for adherence to standardization procedures. After awakening a questionnaire was completed involving self-reports about the quality and amount of sleep along with an SSS. Body temperature, heart rate, and urine were tested to clarify data about circadian rhythmicity. (constant rectal temperature probes were used and all urine was collected to examine hormone levels).
NASA investigators found most crew members were able to get enough sleep during layover either by sleeping well at selected times or by sleeping less efficiently but staying in bed longer; sleep quality declined slightly in most cases; more so after eastward flights. Older (over 50 years) crew members got less total sleep and had poorer quality sleep. The human circadian rhythm is not only more disrupted by eastward flights, but also causes a longer resynchronization period. Sleep duration varies with the circadian temperature, the longer sleeps occur when the temperature is lower.
The study also showed that there is definite variance between individuals due to circadian type; some are morning and some are night people. Similarities were found in the baseline daytime sleep latency curves; all showed a gradual increase in sleepiness during the day with a maximum in the late afternoon followed by a gradual decrease in the evening; these sleepiness rhythms continued after the time zone shift when back to home. It is possible that crews could predict the easiest times to fall asleep and thus develop good strategies for sleeping away from home. Data obtained after eastward flights showed that " adhering to more structured sleep schedules and limiting initial post-flight sleep would appear to facilitate the acquisition of adequate sleep during the layover." 5
Jet lag is a psychological and physiological stress on the body; studies on stress have shown that the more stress in your life the higher your odds are of becoming ill. Studies on lab animals show that when their biological clocks are tampered with they are subject to higher death rates when exposed to toxic chemicals, alcohol, medications and toxins from certain bacteria. Norman Cousins wrote about a serious illness he experienced after returning from a trip to Russia; he describes his perception of the illness in "Anatomy of an Illness" in New England Journal of Medicine, vol 295, Dec 23, 1976, pp. 1458-63; although Cousins did not say that jet lag was the cause, it is possible according to Dr. J. Greist and Dr. G. Greist. 6
The short and long-term effects of a single or repeated experience with jet lag on our health have not been proven as yet; the type of studies that would be needed to prove the health effects would be very hard to do. Several factors are likely to be determining factors in how much we are affected by jet lag: the number of time zones crossed, the number of recent exposure to jet lag, and sleep loss. An interesting difference between the United States and the Soviet Union is that the Soviets assume that a change in the circadian rhythm would lead to deleterious effects; their cosmonauts maintain their earthly day/night cycles even while in orbit. The United States uses a variety of schedules; apparently, we expect flexibility in ourselves.
According to Dr. Strughold, Dr. R. F. Fitch, Chief of Internal Medicine at Wilford Hall USAF Medical Center, San Antonio, Texas, "the administration of hormone-containing drugs should simulate the natural circadian production pattern of the hormones, to avoid disturbing their role in running the physiological clock." 7
It has been reported that transplanted kidneys take about a year to get it together with their new body. Internal cardiac pacemakers automatically beat ten beats per minute slower at night.
The effects of jet lag can have serious meanings to those whose mission involves international political conferences; businessmen traveling abroad hoping to complete transactions involving large sums of money; and Olympic athletes must do all they can to resynchronize themselves. Numerous methods have been suggested to help minimize the effects of jet lag:
Preflight adaptation is one; try to slowly adapt yourself to the time zone of your destination; if traveling east, go to bed and arise two or more hours earlier and gradually shift meal times so they are more in line with your destination. If traveling west, stay up later and get up later than usual. If possible plan to fly to your destination a couple of days ahead of time so you can become adjusted before your planned activity. President Eisenhower did this in 1955 before meeting Nikita Khrushchev in Geneva for a Summit meeting. 8
Some companies have a rule that their executives are not to sign any contracts within the first two days after a transoceanic flight. If you are unable to take time ahead for adaptation be aware that the morning hours in the first few days after eastbound and the late afternoon after westbound are times to avoid in signing contracts, making major decisions, or conducting affairs of state.
After arriving at your destination spend as much time as possible out in the sunlight, letting the sunlight help to reset your clock. Joan Hamilton in Business Week magazine says that Czeisler, associate professor of medicine at Harvard, foresees that in the future airplanes may adjust their interior light to help reset our biological clocks. 9
Socialize to stay awake and avoid daytime dozing. According to Joan Hamilton in Business Week magazine, frequent flyers get over jet lag sooner when they force themselves to socialize; she quoted a pharmacologist at Florida A&M University as saying, "We know that extroverts seem to get over jet lag faster than introverts." 10
Low humidity in airplanes can result in loss of water; this can lead to changes in electrolyte levels(sodium, potassium, and chloride); it is recommended that extra water is a good idea because dehydration can cause fatigue, sleep disturbances, and a reduced capacity to reset the biological clock.
Alcohol and caffeine should be taken only in extreme moderation; they have the ability to turn off the body's antidiuretic hormone, this causes water loss which in turn will also dehydrate you. Also the pressurized cabin at five to six thousand feet above sea level makes two drinks (of alcohol) have the same effect as three.
The gastrointestinal system operates with rhythmic periods of high and low, so if you eat a big meal at a time when your stomach thinks it should be asleep you are just adding to the burden of time zone adjustment for your stomach. Gradually shift meal time to that of your destination. For this reason, eat lightly and at the correct time according to your destination. Increased altitude causes gas in your gastrointestinal tract to expand; carbonated beverages will thus have a worse effect than on the ground.
It will help to make your transition easier if you rest at home before you leave; sleep or at least resting on a long flight will help, a short-acting sleeping pill may help also; Halcion and Restoril are two short-acting prescription products recommended. 11
"Intellectual function is often more noticeably affected than other biological functions". 12 For this reason diplomats, business people, and flight crews need to really take care.
According to the editors of Discover and B. Bower in Science News magazines, researchers N. Mrosovsky and P. Salmon at the University of Toronto after experiments with hamsters think that exercise may help to speed up the resetting of our jet-lagged clocks. Their study showed that active hamsters needed 1.5 days to adjust while lazy hamsters took up to 11 days. 13-14
People who work nights or periodically change shifts encounter symptoms very much like jet lag; in addition, police officers were shown to have high rates of alcoholism, sleeping pill use, accidents, and family disruptions. Lisa Bain says in Psychology Today, that neuroscientist, Charles Czeisler, of Harvard Medical School claims that "the problem is in the schedule, not the job." 15
Czeisler redesigned their schedule to better accommodate their circadian rhythm. There were three basic changes: one, instead of changing shifts every eight days, they changed every eighteen days; second, they changed shifts going from days to evenings and then to nights; third, Czeisler had the officers work only four days in a row so they could catch up on their sleep.
The results after about a year were positive: The officers had less sleep problems and were generally more alert; car accidents were down by forty percent; alcohol and sleeping pill use were down fifty percent; the families felt five times better after the new schedule. Czeisler says that workers who have their circadian rhythms desynchronized frequently are functioning in an impaired state; public safety is thus a concern.
End Notes
1 T. Alexander, "Biological Rhythms," Encyclopedia of Psychology, (New York: Wiley, 1984), vol 1 pp. 151.
2 Hubertus, Strughold, M.D., Your Body Clock (New York: Scribner, 1971), pp. 41.
3 Strughold, pp. 57. Dr. Strughold says that Dr. William Douglas, flight surgeon to the Project Mercury astronauts suggests this rule.
4 Arthur, Winfree, The Timing Of Biological Clocks, (New York: Scientific American, 1987), pp. 4-5.
5 Graeber et al, "International Aircrew Sleep and Wakefulness After Multiple Time Zone Flights: A Cooperative Study," Aviation, Space and Environmental Medicine, (Dec 1986, vol 57 (12, Sect II)), pp. 9.
6 John Greist, M.D., and Georgia Greist, Ph.D., Fearless Flying, (Chicago: Nelson-Hall, 1981), pp. 71.
7 Strughold, pp. 32.
8 Strughold, pp. 61.
9 Joan Hamilton, "You Don't Have to Give in to Jet Lag," Business Week, (Oct, 26, 1987) pp. 126.
10 Hamilton, pp. 126.
11 Editors of Changing Times, "Unsag From Jet Lag," (May, 1988) pp. 104.
12 Greist, pp. 75.
13 Editors of Discover, "Overcoming Jet Lag: The Rodent Way," (May 1988,) pp. 18.
14 B. Bower, "Hamster Jet Lag: Running it Off, Science News, (Dec 5, 1987 vol 132: no 23) pp. 358.
15 Lisa Bain, "Night Beat", Psychology Today, June 1988 vol 22, pp. 14-15.
Bibliography
Alexander, T. "Biological Rhythms." Encyclopedia of Psychology. New York: Wiley, 1984. vol 1.
Carlson, Bruce. "Pineal Gland." Encyclopedia Americana. ed. Danbury: Grolier, 1986.
"Circadian Rhythms in Metabolic Activity." Encyclopedia Britannica. New York: U of Chicago P. 1988. vol 25:487:2a.
Bain, Lisa. "Night Beat." Psychology Today. June 1988: vol 22.
Bower, B. "Hamster Jet Lag: Running it Off." Science News. Dec 5, 1987. vol 132: no 23.
DuHamel, Meredith. "Traveling Through Time." Women's Sport and Fitness. Dec, 1987. vol 9: no 12
"Effects of Light on Biological Rhythms." Encyclopedia Britannica. New York: U of Chicago P, 1988. vol: 26: 519:2b.
Graeber, et al. "International Aircrew Sleep and Wakefulness After Multiple Time Zone Flights: A Cooperative Study." Aviation, Space and Environmental Medicine. Dec, 1986: vol 57 (12, Sect II).
Greist, John, M.D. and Greist, Georgia, Ph.D. Fearless Flying. Chicago: Nelson-Hall, 1981.
Guyton, Arthur, M.D., "Circadian Rhythm of Glucocorticoid Secretion." The Textbook of Medical Physiology. 7th ed. Philadelphia: Saunders, 1986.
Hamilton, Joan. "You Don't Have to Give in to Jet Lag." Business Week. Oct 26, 1987.
Kalland, Gene. "How to Reduce Jet Lag." USA Today. June 1988. vol 116: no 2517.
Kalat, James. "Endogenous Circadian and Circannual Rhythms." Biological Psychology. 3rd ed. Belmont: Wadsworth, 1988.
Luce, Gay. Body Time. New York: Pantheon Books, 1971.
Morin, Lawrence. "Biological Clock." Academic American. Danbury: Grolier, 1987. vol 3:264-265.
"Overcoming Jet Lag, the Rodent Way." Discover. May 1988.
Sakmar, M.D., Gardner, M.D., and Peterson, M.D., Ph.D. Health Guide For International Travelers. Passport Books, 1984.
Strughold, Hubertus, M.D. Your Body Clock. New York: Scribner, 1971.
"Time Dislocation: The Jet Syndrome." Encyclopedia Britannica. New York: U of Chicago P. vol 14: 641: 2b.
"Unsag From Jet Lag." Changing Times. May 1988.
Wegmann et al. "Sleep, Sleepiness, and Circadian Rhythmicity in Aircrew Operations on Transatlantic Routes." Aviation, Space and Environmental Medicine. Dec 1986. vol 57 (12, Sect II).
Winfree, Arthur. The Timing of Biological Clocks. New York: Scientific American, 1987.
