Jet lag

Jet lag is a condition well known to travelers since the introduction of passenger jet aircraft. It is an informal term for the symptoms that occur when travelers rapidly cross several time zones and attempt to follow the time schedule of the new destination. The condition manifests itself differently among individuals, and the symptoms increase with age and number of time zones crossed. Eastward travel is generally more difficult than westward travel. The adjustment to a new time zone is mediated by the suprachiasmatic nucleus, which acts as our primary internal timekeeper and regulates diurnal variations in body temperature and the release of melatonin, cortisol, and growth hormone. These hormones are important in maintaining circadian rhythm. The time required to resynchronize the release of these hormones and thus reset the internal clock is generally agreed to be about 1 day per time zone crossed. A number of therapies and behaviors have been recommended to reduce jet lag, but the American Academy of Sleep Medicine guidelines give the strongest recommendation to the use of melatonin as a standard therapy based on high levels of evidence. Light therapy with sleep time adjustment can also help speed the resolution of circadian dyssynchrony.