Jet lag

A sleep disorder resulting from crossing time zones in too rapidlyfor the circadian clock to keep pace;

Refers to a temporary misalignment between the circadian clock and the local time.

Jet lag disorder occurs when the circadian rhythm is not in sync with the destination time.

Leads to daytime fatigue and increases negative moods, increases depression and anxiety symptoms, exacerbates preexisting psychiatric disorders, impairs memory and innovation.

Increases seizure frequency in patients with epilepsy.

In the dark the pineal gland produces melatonin, which promotes sleep.

Daylight inhibits melatonin production and so allows wakefulness during the daytime.

Treatment strategy uses melatonin to help induce sleep and uses daylight to help keep awake to shift the circadian rhythm faster to match the destination time.

The melatonin dose is between 0.5 mg and 5 mg, with the higher dose giving faster and better sleep.

Sleep disturbances associated with air travel can result in cognitive and physiologic impairments.

May result in sleep deprivation, which may cause reduced attention, vigilance, mood disorders, impaired memory, and alteration in executive function.

Frequently encountered by air travelers traversing multiple time zones.

The circadian clock is located in the hypothalamus, the suprachiasmatic nucleus, and is normally synchronized to the solar light-dark cycle, and promotes alertness during the day and sleep at night.

When time zones have been crossed in a rapid fashion the circadian clock is too slow to reset and the endogenous sleep and wakefulness signals do not match the local light-dark and social schedules.

Symptoms secondary to jet lag, include insomnia, dysphoric mood, cognitive impairment, diminished physical abilities, and gastrointestinal upset.

Travel fatigue often accompanies jet lag and is related to prolonged immobility, irregularity in sleep times, irregularity in mealtimes, and dehydration.

Travel fatigue, generally reverses in 1 to 2 days, with diet rest and sleep.

Jet lag persists until the circadian rhythm is realigned.

Usually benign and self-limited.

Incidence is unknown but is a common process in people who travel across five were more time zones.

May be a recurrent or chronic process among frequent long-distance travelers.

Management includes: realignment of the circadian clock with timed exposure to light, the use of melatonin, the optimal timing of sleep, and use of medications for insomnia, and to prevent daytime sleepiness.

It is estimated that the circadian clock resets an average of 92 minutes later each day after a westward flight and 57 minutes earlier after an eastward flight (Aschoff J).

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