Etiology
The severity of the symptoms is directly proportional to the number of time zones crossed. Westbound travel leads to less disruption because it is easier to phase-delay rather than to phase-advance the natural circadian cycle.[1] Readjustment occurs at a rate of about 1 hour per day during eastward travel and at about 1.5 hours per day during westward travel. Several factors can predispose a traveler to or precipitate symptoms of jet lag, such as stress, excessive caffeine or alcohol use, and sleep deprivation.
Pathophysiology
Various endogenous circadian body rhythms are regulated by an internal pacemaker, the suprachiasmatic nucleus.[2] These rhythms are influenced and are in synchrony with environmental cues by a process known as entrainment. The environmental variables that are capable of entraining circadian rhythms are known as entraining agents or Zeitgebers. Light is the most effective Zeitgeber, but temperature, food availability, and social interactions also play a role.[2][3] After time zone transitions, body rhythms shift out of phase with the Zeitgebers. Upon arrival at the destination, the traveler experiences a mismatch between the internal circadian rhythms, including sleep-wake cycle, and local environmental cues. Gradually, the Zeitgebers shift the internal body rhythms in synchrony with the environment. Until this synchrony happens, travelers continue to experience symptoms of jet lag.[2]
Classification
International classification of sleep disorders, 3rd edition, text revision (ICSD-3-TR)[1]
Circadian rhythm sleep-wake disorders
Jet lag disorder
Temporary mismatch between internal circadian clock and outside environmental cues due to rapid travel across time zones.
Shift-work disorder
Transient insomnia or excessive sleepiness phenomena related to work schedules that take place during the normal sleep period.
Delayed sleep-wake phase disorder
Late-timed sleep pattern in which the onset of the major sleep period is delayed 2 or more hours than desired, leading to a later waking time. Typically occurs in adolescence.
Advanced sleep-wake phase disorder
Early-timed sleep pattern in which onset of the major sleep period occurs 2 or more hours earlier than desired, leading to an early waking time.
Non 24-hour sleep-wake rhythm disorder
Occurs in individuals with nonentrained circadian rhythms, resulting in sleep onset or offset delayed by 1 to 2 hours. Most people with this disorder are blind.
Irregular sleep-wake rhythm disorder
Irregular pattern without a clearly defined circadian rhythm of sleep and wake, observed most commonly in neurodegenerative disorders, such as dementia, and in children with developmental disorders.
Circadian sleep-wake disorder not otherwise specified (NOS)
Meet criteria for a circadian rhythm sleep-wake disorder but do not fit into one of the specific types listed above.
Use of this content is subject to our disclaimer