Air travel can result in disrupted sleep, associated fatigue and tiredness. The ability to traverse time zones faster than our internal clock, also known as the circadian rhythm, can catch up results in a disruption of of our sleep wake cycles.
This is jet lag, it impairs alertness and makes it difficult to sleep well at your final destination.
What are Circadian rhythms?
This is the process that allows you to respond appropriately to the changes in sun exposure caused by the rotation of the earth. One of the most important functions of this system is the sleep wake cycle which is usually aligned to the dark and light cycles of a typical day.
This sleep wake cycle is affected by the secretion of melatonin and the change in your core body temperature.
Melatonin is a hormone secreted by the pineal gland (a small endocrine organ located in the brain) and is thought to help with regulating the sleep-wake cycle.
The body makes and secretes melatonin at night. Levels go up at night and drop in the morning.
You can buy melatonin supplements over the counter. It’s recommended to start taking it the first night at your new location right before going to sleep. Keep in mind that everybody reacts differently to medication and supplements so it may or may not work for you.
Normally, melatonin levels begin to rise as the sun starts to go down. This increase in melatonin is associated with a drop in the core body temperature. These two factors lead to the decreased level of alertness or more commonly, sleepiness.
As the sun starts to rise, the melatonin levels start to drop and the core body temperature starts to rise. This promotes wakefulness.
This rhythm and its timing are modifiable. For example, melatonin supplements can shift the circadian clock. The effect depends on when the exogenous melatonin is ingested. If taken in the early evening it advances the circadian rhythm. However, if taken in the morning, it can delay the phase.
The circadian clock is modifiable, but phase shifts do not occur instantaneously after a change in the light-dark cycle precipitated by travel. It can take several days or more.
This mean that your internal clock will remain set to the time of origin immediately after the change in light-dark cycle. The degree of dyssynchrony between the internal clock and external light-dark cycle depends on the number of time zones crossed.
Symptoms of Jet Lag
Typically, symptoms of jet lag occur one to two days after travel across at least two time zones. This includes disturbed sleep, excessive daytime sleepiness, generalized fatigue, and impaired daytime functioning.
Inability to sleep caused by jet lag is manifested by difficulties with both sleep onset and maintenance. This is the result of the overlap of high circadian alerting signal with the desired time for sleep.
Excessive daytime sleepiness
This occurs due to the overlap of high sleep propensity with the desired time for being awake in the new time zone. Accumulated sleep debt related to unsuccessful attempts to sleep when the circadian system is promoting alertness also contributes to daytime sleepiness.
Mental and physical impairment induced by jet lag result from decreased alertness and circadian misalignment.
Untreated, the circadian timing system will adjust to the destination time by roughly one time zone per day for eastward travel and 1.5 time zones per day for westward travel. In addition to distance traveled, the severity of jet lag is influenced by multiple factors and ultimately depends on the traveler.
Although self-limited, jet lag can have significant repercussions in those who require high levels of performance immediately after international travel.
How do you know if you have jet lag?
The diagnosis of jet lag is based on criteria put forth by the International Classification of Sleep Disorders (ICSD), and include the following features:
●Insomnia or excessive daytime sleepiness associated with a reduction of total sleep time coinciding with jet travel across at least two time zones
●Impaired daytime function, general fatigue, or somatic symptoms that begin within two days of travel
●The sleep disturbance cannot be explained by another disorder
The goal when you have jet lag is to improve symptoms of insomnia and excessive daytime sleepiness. The strategy for treatment is to align the internal circadian phase with the new light-dark cycle in the destination time zone.
This will result in improved sleep and alertness at the desired times. This adjustment will occur naturally without treatment. However, use of light and melatonin can help shorten this process.
Trips lasting only one or two days are generally too short to expect adjustment to the destination time zone.
Longer trips (three or more days)
Eastward travel requires an advance of the circadian timing system to adjust to the new time zone, and appropriately timed light exposure and exogenous melatonin can hasten adjustment.
Timed light exposure
The proper timing of both light and melatonin for eastward travel is based on circadian physiology. Appropriately timed light exposure can result in phase advances of about 1.5 hours per day. Treatment timing should therefore be adjusted daily, one hour earlier per day with eastward travel.
Prior to travel
If you are highly motivated, you can start bright light therapy up to three days prior to departure. This will help to advance the circadian phase and reduce the degree of dyssynchrony upon arrival at the destination.
The source of light can be either natural outdoor daylight or a light box. You should wake up about one hour earlier than their usual wake time and seek exposure to bright light for at least one hour. This is repeated daily for up to three days prior to departure, successively advancing the wake time. Bedtimes should be similarly advanced one hour earlier each night if possible.
Upon arrival at the destination after eastward travel, strategic light exposure and light avoidance can be timed to help advance the internal circadian phase. The best source of light is sunlight. A light box can also be used.
For trips crossing three to five time zones, this generally means avoiding bright daylight first thing in the morning at the destination, and then seeking out several hours of bright light beginning mid- to late-morning.
For trips crossing six or seven time zones, bright light should generally be avoided during the morning on the day of arrival and sought out in the early afternoon. In both cases, light exposure can then be shifted gradually earlier on successive days.
To help advance the circadian phase after eastward travel across multiple time zones, the appropriate timing of melatonin is in the evening, at the desired destination bedtime.
Taking melatonin at bedtime upon arrival helps with phase advance and also takes advantage of the possible sedative effects of melatonin.
Starting melatonin on the evening of arrival and continuing for up to five days is recommended at doses that range from 0.5 to 10 mg. Usually, 3 mg of melatonin is sufficient, and some find immediate formulations more effective than delayed release.
All medications and supplements can have side effects. The side effects from melatonin are fairly mild and include vague symptoms that are very similar to jet lag itself. Before taking any medication or supplement, discuss it with your doctor to make sure it is safe for you.
While melatonin is relatively benign, it can interact with certain medications. We don’t use melatonin when we travel and don’t recommend it except as a last resort option.
Caffeine and other stimulants
Caffeine is generally safe and can help offset daytime sleepiness associated with jet lag, but benefits may be outweighed by sleep disruption. After eastward travel, caffeine can improve sleepiness when compared with melatonin and placebo and also hastened circadian entrainment. However, sleep onset latency and awakenings may be increased.
Napping is a reasonable strategy to combat decreased alertness due to sleep loss. To avoid nighttime sleep disruption, naps should be less than 30 minutes long and at least 8 hours before the anticipated bedtime.
Westward travel requires a delay of the circadian timing system to adjust to the new time zone. Appropriately timed light exposure can achieve phase delays of about 2.5 hours per day. Melatonin is generally not needed for westward trips but may provide some benefit.
Timed light exposure
Upon arrival at the destination after westward travel, light exposure and avoidance can be strategically timed to help delay the internal circadian phase. The best source of light is direct, outdoor sunlight. A light box can also be used.
As with eastward travel, short naps and caffeine can help offset daytime sleepiness associated with jet lag after westward travel.
The dry air on an airplane can cause dehydration. Dehydration can worsen the symptoms of jet lag. Best way to avoid dehydration when flying, don’t drink alcohol! Both alcoholic beverages and coffee can exacerbate dehydration, so if possible it is best to avoid both. Instead, drink plenty of water. The rule of thumb is you should drink enough water that you have you have to get up to urinate about every hour while on your flight.
To sum it all up.
The most important thing about jet lag is that it gets better on its own as one adjusts to the new time zone. This can take several days. Taking melatonin supplements may help some adjust quicker. Staying well hydrated helps as well. The farther you travel from home, the longer it takes to get over jet lag.
Please remember that medical information provided by us must be considered an educational service only. This blog should not be relied upon as medical judgement and does not replace your physician’s independent judgement. Please seek the advice of your physician.