Facts of Life:
Issue Briefings for Health Reporters
Vol. 8, No. 7
July 2003

On the Go:
The Health Concerns of Travel

The Issue

The Facts

Jet Lag: Tricking the Body’s Clock

Expert Sources

References

The SARS virus may be the tourist’s scourge of 2003, but its frightening appearance is nothing new in the world of travel medicine. Since the beginning of travel, people have carried different diseases and immunities and a variety of risky behaviors with them.

• Sixty-six percent of Asian travelers, 64 percent of American travelers and 48 percent of European travelers do not seek medical advice before traveling to an area with a risk of infectious disease. [3]
  
• Ear pain is the most common complaint of airplane travelers. Some frequent flyers use nasal decongestants to shrink their nasal membranes in an attempt to make the ears pop more easily, but a Mayo Clinic study suggests that decongestants do not relieve similar earaches in children. [4]
  
• In the United States, individual states can declare disease quarantines within their own borders. The Centers for Disease Control and Prevention are also authorized to quarantine any individual suspected of carrying certain communicable diseases. [5]
  
• Passengers flying on airplanes with re-circulated air do not catch colds any more frequently than passengers on planes that use fresh air for ventilation, according to a University of California, San Francisco study. [7]
  
• According to a recent CDC report, rates of diarrheal illness aboard cruise ships dropped 44 percent from 1990 to 2000, thanks in part to improved sanitation standards. [8]
  
• Although the number of plane passengers who say that flying is stressful rose from 60 percent in July 2001 to 81 percent in February of 2002, only 2 percent of fliers say that terrorism concerns are their main worry. Instead, commercial air travelers feel most stressed by long waits, lines and increased security controls at airports. [8]
  
• Hepatitis A is the most common vaccine-preventable disease in travelers. Even without a vaccine, however, the CDC says that many infections can be prevented by simple behaviors like peeling fruits and vegetables and using bottled water for drinking and tooth brushing. [9]
  
• People may be more apt when traveling to practice risky behaviors like having sex with strangers, using injection drugs or getting tattooed, according to a report by the World Health Organization. [10]
  
• Most health insurance plans, including federal programs like Medicare, do not cover hospitalization or other medical costs outside the United States. [11]
  
• Information about travel advisories, disease outbreaks around the globe, vaccination suggestions and other items of concern to international and domestic travelers can be found at http://www.cdc.gov/travel.
  

Five years ago researchers from Cornell University Medical College startled long-haul fliers by announcing a possible way to beat jet lag.

Their experiments seemed to show that light shined on the back of the knee could reset a person’s biological clock, bringing a traveler into balance with a new time zone. [12] But the Cornell success proved difficult for other scientists to replicate, and a careful analysis of the study in 2002 [13] suggested that this jet lag cure might be, well, a flash in the pan.

Jet lag affects 94 percent of people who travel across multiple time zones, and as many as 96 percent of airline pilots and flight attendants live in a permanent state of jet lag, says Mary Carskadon, Ph.D., a sleep researcher at Brown University. Along with fatigue and insomnia, jet lag also can raise stress hormone levels and blood pressure and cause an irregular heartbeat and swollen limbs. Jet lag also may exacerbate depression and other mental disorders like schizophrenia.

“It is only recently that science has taken this disorder seriously and taken steps to find suitable treatments for it,” Carskadon says.

The problem lies in the mismatch between the body’s internal daily rhythm and the light cues it gets from outside.

Certain nerve cells in the brain keep the body functioning on a 24-hour cycle that affects sleep and other daily rhythms. This master timekeeper depends on light coming through the eyes to stimulate these cells and synchronize the cycle with day and night.

Treatment Options

Clinicians often recommend bright light therapy to counter severe jet lag, but this can overwhelm the eyes. Other approaches include small doses of melatonin, one of the body’s pace-setting hormones. Melatonin appears to protect clock cells from inadvertently being reset by bursts of activity in other brain cells. This protective function might explain why melatonin also seems to work as a sleep aid, but it also means that an incorrect dose can aggravate jet lag, sleep researcher Mary Carskadon says.

Other mildly successful remedies include slow-release caffeine pills and exercise after a flight, but researchers are not sure exactly how these treatments work. Most people take one day for every time zone crossed to return to a normal sleep pattern, so patience is still the best “cure.”