What is Jet Lag?
Circadian rhythms are biological rhythms that drive changes within humans. For example, we have circadian rhythms of alertness and body temperature. Usually these rhythms align with the environment’s natural light and dark cycle: peak drowsiness occurs around 5:00 AM, when it is often dark out. Jet lag occurs when our rhythms no longer align with the environment. Flying from Vancouver to Moscow — 12 hours ahead — means that peak drowsiness occurs at 5:00 PM, when one would usually want to be alert.
Our internal clocks are regulated by “Zeitgebers” which are rhythmic cues in the environment that synchronize the internal body clock to the earth’s 24-hour light–dark cycle. Light is the strongest Zeitgeber; other non-photic Zeitgebers include temperature, social interaction, pharmacological manipulation, exercise, and meal timing.
A multitude of factors, such as the number of time zones crossed and the direction and timing of flights, play a role in the severity of symptoms experienced by travelers. You may notice some are affected more than others because there is much individual variability in each person’s ability to adapt. Travelers usually experience symptoms after air travel across at least two time zones. Symptoms may include disturbed sleep, daytime fatigue, decreased ability to perform mental and physical tasks, reduced alertness, and headaches. Sleep disturbances typically last for a few days, but they can persist for as long as one week if the change in time zones is greater than eight hours. Eastward travel is associated with a longer duration of jet lag than westward travel. More serious side effects have included cognitive deficits, gastrointestinal disturbances, and an increased risk of cancer, infertility, and heart disease. And as you may have experienced, as the body’s internal circadian “clock” adapts to the new time zone, jet lag diminishes.
What are the common treatments?
You probably know the basics from the National Sleep Foundation:
- Select a flight that allows early evening arrival and stay up until 10 p.m. local time. (If you must sleep during the day, take a short nap in the early afternoon, but no longer than two hours. Set an alarm to be sure not to over sleep.)
- Anticipate the time change for trips by getting up and going to bed earlier several days prior to an eastward trip and later for a westward trip.
- Upon boarding the plane, change your watch to the destination time zone.
- Avoid alcohol or caffeine at least three to four hours before bedtime. Both act as “stimulants” and prevent sleep.
- Upon arrival at a destination, avoid heavy meals (a snack—not chocolate—is okay).
- Avoid any heavy exercise close to bedtime. (Light exercise earlier in the day is fine.)
- Bring earplugs and blindfolds to help dampen noise and block out unwanted light while sleeping.
- Try to get outside in the sunlight whenever possible. Daylight is a powerful stimulant for regulating the biological clock. (Staying indoors worsens jet lag.)
- Contrary to popular belief, the type of foods we eat have no effect on minimizing jet lag.
Are there better ways to change your sleep time rather than simply going to bed later or earlier? Strategies to minimize the effects of jet lag include adjusting the sleep schedule according to the new location during the days preceding the trip. Note that this approach is helpful for travel that lasts for more than a week, but it does not appear useful for short-term trips. Both alcohol and caffeine can adversely affect quality of sleep when they are consumed a few hours before bedtime; caffeine intake should be planned to enhance daytime alertness. When passengers are traveling, they are advised to avoid alcohol, especially while they are being treated for jet lag.
Treatment may include non-pharmacological therapy alone or non-pharmacological therapy combined with nutraceuticals or medication therapy. Remember that some sleep aids can be addictive. Nutraceuticals and over-the-counter therapies like melatonin, caffeine, or Benadryl are commonly used, or your medical provider can decide if prescription agents are appropriate for you. A non-pharmacological approach, including adequate exercise, hydration, and appropriate timing of exposure to bright light, can aid in the adjustment to a new time zone.
Sunlight has a major influence on the internal circadian clock. Traveling across several time zones requires resetting and adjusting to a new daylight schedule. Natural light exposure is the ideal mechanism for counteracting jet lag.
For those who travel frequently and are unable to have exposure to natural sunlight, light therapy may be a viable option. Light synchronizes the body clock by exposing the eyes to an artificial bright light that simulates sunlight for brief periods at planned times during the day. Various modalities include a light box, a lamp, and a light visor.
Bright light exposure is the most powerful way to cause a phase shift — an advance or delay in circadian rhythms. Light in the early morning makes you wake up earlier (“phase advance”); light around bed time makes you wake up later (“phase delay”).
Calculating when to seek and avoid light depends on the number of time zones crossed, direction of travel, and usual wake and sleep times. These calculations can be done automatically online, or manually by following some rough guidelines:
- Estimate when your body temperature reaches a minimum. If sleeping 7 or fewer hours per night, assume this is 2 hours before your usual wake time. If sleeping more, assume this is 3 hours before your usual wake time.
- Determine whether you need to advance or delay your circadian rhythms. If you are flying east (to a later time zone), such as from Los Angeles to New York, you will need to phase advance. Otherwise, if you are flying west, you will need to phase delay.
- If you need to phase advance, avoid light for 4 hours before your body temperature minimum, and seek light for 4 hours after it. (This included avoiding light from tablets, televisions and phones!) Otherwise, do the opposite. Light boxes become very important to keep light exposure on your planned schedule with artificial bright light.
- Shift your estimated body temperature minimum time by one hour earlier per day if phase advancing, or one and a half hours later per day if phase delaying until you get to or move closer to the desired waking time. Cooling mattress pads can be helpful to actually regulate your body temperature on schedule and help you to sleep better before a phase shift, so that you are starting with a good sleep base — click here to see more.
- The pre-adaptation schedule to follow will depend upon the number of time zones to be crossed, your sleep schedule at home and at the destination, and the number of days available to try and adapt.
Here are two examples:
Imagine that you are flying 5 time zones eastwards from New York to London then you would need to shift your body clock earlier in time by 5 hours and to do this you can use early morning light. You can begin your shifting schedule 5 days before the flight. Each day you should shift your bed time and wake time ~1 hour earlier. So if you normally sleep 11pm – 7am, 5 days before the flight you should get up at 6am and to go bed at 10pm, 4 days before the flight you should get up at 5am and go to bed at 9pm etc. In addition to shifting your sleep times, upon awakening you should also expose yourself to light for at least an hour. The use of the light box does not need to be continuous and short breaks for showering or making breakfast will not reduce its effectiveness. This sort of schedule is the ideal but may not be possible for everyone if they still need to go to work or college in the days before their flight. However, even shifting by 30 minutes per day for 5 days or just shifting by 2 hour during the last 2 days before flying will help to adapt the clock and reduce the duration of jet lag.
To prepare for a westward flight your clock needs to be gradually shifted later in time and therefore evening light should be used. If you imagine that you are making the return flight from London to New York then you will need to shift your body clock 5 hours later in time. Beginning 5 days before your flight you should shift your sleep times later by 1 hour each day e.g. from 11pm – 7am to 12am – 8am 5 days before flying, 1 – 9am 4 days before flying etc. In addition, you should use bright light for at least 1 hour before you go to bed.
Bodyclock Active 250 is an alarm clock that wakes you with a gradually brightening sunrise and has a range of wake-up options. Choose a short 15-minute sunrise or up to 90 minutes for a more gradual effect. Early birds could also add dawn chorus or rooster wake-up sounds. The FM radio gives you the option of waking up to your favorite station.
Bodyclock Active 250 has a slowly fading sunset option, perfect for phase delaying. To continue a great base of sleep before you start globetrotting it has two optional sleep sounds – to help you naturally relax, and stay asleep.
Other features include nightlight and a security option that turns the light on while you’re away to help with peace of mind.
Other features include:
- FM radio with digital tuning
- Gradual sunrise of 15, 20, 30, 45, 60 or 90 minutes to wake naturally
- Fading sunset of 15, 20, 30, 45, 60 or 90 minutes to wind down for sleep
- Alarm beep (optional) plus 4 sleep/wake-up sounds: Dawn chorus, Rooster, Waves, White noise
- Nightlight option for fading light that stays on at low level
- Security option turns on the light in the evening while you’re away
- The Sunray effect is important for the longer duration of light exposure.
- Fully dimmable display / Snooze / Optional alarm beep / Power failure back-up
If you want to use a simple SAD lamp there are many available on Amazon. Click the photos below to see popular models.
Melatonin’s utility in the management of jet lag has been the subject of many studies. When making travel plans, particularly over a distance of five or more time zones, travelers should take melatonin on the day of travel at the projected nighttime hour in the new time zone and on subsequent days in the new time zone. In the case of flights that cross seven to eight time zones, it may be beneficial to initiate melatonin when beginning light therapy for phase shift.
Common adverse effects of melatonin have included daytime sleepiness, dizziness, headache, and loss of appetite and these are more common when you use doses above 5 mg, so doses ranging from 0.5 mg to 5 mg are recommended to use for phase shift of your sleep.
Remember, if you have questions related to your health, always consult your doctor or medical professional. The information presented here is informative only and is not medical advice.