Finding the key to jet lag: It’s about time
As the old song goes, “Changes in latitudes, changes in attitudes,” and for anyone who has been wide awake at 3 in the morning after a cross-country jaunt, this attitude might best be described as seriously out of sorts.
“The feeling is like lead in my veins,” says Elfi Stoddard, who has been a flight attendant since 1975 and for the last 18 years has been based in Honolulu for Hawaiian Airlines. “I am very tired but can’t go to sleep, and very irritable so I snap at my family.”
Whether it is a trip east or a trip west, shifting time zones often wreaks havoc on sleep cycles, which leads to the awful sense of disorientation, general discomfort and irritability that characterizes a condition known to most people as jet lag but to experts as desynchronization. (And to be precise, changes in latitudes alone aren’t usually a problem -- it’s the changes in longitude that pack a wallop.)
Several surveys of airline passengers and flight attendants have demonstrated what Stoddard knows only too well: More than 90% of long-haul travelers, no matter how much they fly, experience some form of the problem. Although most will at worst snap at family members or be grumpy with colleagues, actor Russell Crowe has said jet lag was the reason that he recently heaved a telephone at a hotel employee.
But why do we get jet lag?
Usually the explanation zeroes in on behaviors that seem to be controllable: not drinking enough water during travel, drinking alcohol, cramped seats, cabin pressure and, as Stoddard says, “lack of sleep when you are used to sleep.” And yet drinking water, walking around during the flight and trying to get sufficient rest often do little to alleviate the symptoms.
Those who suffer also often refer to an internal clock getting thrown out of whack. As it turns out, this is not just a metaphor. At the base of our brains is such a clock, the brain’s central timekeeper. It is called the suprachiasmatic nucleus, or SCN, and it is located in the part of the brain called the hypothalamus. A number of biologists are beginning to understand how it provides the neural basis for problems with jet lag.
The SCN is filled with neurons, all with synchronized circadian rhythms that help us regulate sleep and wakefulness. Autopsy studies of humans have shown that the suprachiasmatic nucleus influences a number of bodily functions, such as sleep-wake cycles and appetite. Several studies published recently in the journal Current Biology examine the SCN in laboratory rats and reveal some ways this tiny part of the brain can make fliers feel wretched.
In one study, researchers found that the SCN comprises two sections, dorsal and ventral. Rats were exposed to gradually changing periods of light and darkness over seven days until they were in constant darkness. Then researchers looked at changes in their brains and discovered that although the ventral part of the SCN, which is connected to the light-sensitive retina, adjusted very quickly to changes in light, the deeper dorsal area took days to adjust. The signaling pattern between the two sections got confused, which in turn sent confusing messages throughout the rats’ bodies.
Gene Block, a University of Virginia biologist, says this also explains why generally it is harder to adjust to flying east than west. The light sensitive ventral SCN adjusts easily to the light. But the dorsal part simply can’t catch up. The more unexpected light that the ventral part enjoys, the greater the imbalance between the functioning of the two parts of the SCN.
In another study, University of Washington biologist Horacio de la Iglesia exposed a group of rats to artificially created 22-hour days, evenly divided between light and dark. He found that even though the days were shorter, the rats expanded what were their normal daytime activities into the artificial night hours.
Researchers then took a look at the gene expression in the suprachiasmatic nucleus and discovered that when life’s clock was at its normal settings, one set of genes was active during the light period and another during darkness. Confuse the time, however, and both genes are active at the same time. Moreover, says De la Iglesia, “there are peripheral clocks throughout our body, in our liver and in our other organs. We still don’t know what drives them, but it is likely that these genes are there.”
What that means, he says, is that it is not just a matter of the whole body being out of time in the environment. It is as if the times of all the body’s subclocks are out of sync as well. “One day you reset one; the next day you reset the others. And some subclocks reset more quickly than others.”
Although humans aren’t rats, and rats don’t need to know this to plan vacations, the findings may hold some promise for future treatments for jet lag.
Among its many roles, the suprachiasmatic nucleus is also connected to regulating hormones such as melatonin, which helps induce sleep. When the cycle operates the way it should, at bedtime the SCN signals the pituitary gland that it is time to secrete some melatonin to ease the body into a restful sleep. When the SCN has not transitioned to a new time zone, taking a supplement of the hormone melatonin can sometimes substitute for this signal and help get the sleep cycle started.
For the time being, when Stoddard leaves Honolulu at 5 in the evening and flies to Pago Pago, American Samoa, or Papeete, Tahiti, and then, after being on the ground for about an hour and a half, returns to Honolulu at 6 a.m., she needs to rely on her normal strategy.
“I rest prior to my trip. I do use melatonin to help me get some sleep prior to the trip. I take all phones off the hook and darken the room.
“What doesn’t work is just to lie down and hope you can get some rest in the middle of the day.”
