The human body depends on a number of cues to determine a natural sleep/wake cycle, otherwise known as a Circadian rhythm. One of these cues is the difference between light and dark, and another is the natural progression of linear time. Both of these cues can be seriously altered, however, by events such as extended air travel or a shift change at work. The result of these abrupt changes in light and dark cues or local time can be a condition known as jet lag.
Jet lag often strikes airline passengers who are moving between time zones, not within the same time zone. A flight leaving Chicago at 1pm local time, for example, may land roughly at 1pm local time in California. The passengers would still be adjusted to Chicago time, however, so they might experience symptoms of jet lag as their sleep cycle becomes disrupted. The light cues of a California sun may also cause Chicago passengers to feel disoriented or confused at their normal bedtimes.
The symptoms of jet lag can go beyond a temporary confusion or disorientation, however. Some passengers who have traveled across several time zones may experience severe headaches, sinus congestion, general irritability, and even mild depression. The disruption to the passenger's Circadian rhythm may linger for several days, and can be even worse for those who travel from west to east. Gaining several hours of daylight does not appear to be as debilitating as losing hours from a natural bedtime after dark.
Some suggested remedies for jet lag include moderate exercise, maintaining normal eating schedules regardless of local time, and getting sufficient amounts of sleep. Some seasoned air travelers also suggest removing shoes and socks in order for a passenger to rub his or her bare feet on the plane's carpeting. The familiar sensation should help passengers orient themselves after a long flight with few natural cues. While there are currently no miracle cures for the symptoms of jet lag, some preliminary studies on the drug Viagra have suggest it may be have some effect on the feelings of disorientation and confusion some jet-lagged passenger experience. There may be other anti-anxiety or blood pressure medications which produce the same effect. Anti-nausea medications for motion sickness may also have some positive effects on feelings of jet lag as well.