Getting your zzz’s while overseas: A guide to jet lag

It seems like the older (and wiser?) I get, the more I plan for time changes while travelling. There is no worse feeling than not fully soaking in your first few days at an exciting new destination because you lack energy and your brain is in a fog. While jet lag can be hard to avoid, its impact can be minimized. This article discusses why jet lag happens, when it should be anticipated, and what we can do about it.Defining and understanding jet lagJet lag has similarities in impact to the circadian rhythm sleep-wake disorder that can be experienced by those who do shift work:1A persistent or recurrent pattern of sleep disruption that is primarily due to an alteration of the circadian system or to a misalignment between the endogenous circadian rhythm and the sleep-wake schedule required by an individual’s physical environment or social or professional schedule;The sleep disruption leads to excessive sleepiness or insomnia, or both; andThe sleep disturbance causes clinically significant distress or impairment in social, occupational and other important areas of functioning.While considerable variation exists between people, the intensity and duration of symptoms are impacted by:2The number of time zones crossed, increasing in both incidence and severity with more time zones crossed;3The direction of travel, with eastward travel particularly impacted;3The ability to sleep while travelling (e.g., brief naps for short-term relief of jet lag, or longer periods of sleep at times that align with the local time zone); andThe availability and intensity of local circadian time cues upon arrival.Below are strategies that have been tried for jetlag and evidence on their effectiveness.Strategies to adjust circadian rhythmOur circadian rhythm roughly coincides with earth’s 24-hour day/night cycle. It includes a 10–12-hour period at night when the pineal gland secretes higher amounts of melatonin, which supports the nocturnal state.2 However, our body also requires darkness to stimulate this melatonin release, as light exposure is the most important environmental timing cue for our circadian rhythm and is much more influential than knowledge of the current time, regular activity or meal timing.2 For these reasons, bright light exposure and melatonin have been effectively used.Bright light (from natural light or a light box) can adjust our circadian rhythm by about 1.5 hours per day for eastward travel and two hours per day for westward travel.4 Exposure in the morning resets the body clock to an earlier time, whereas exposure in the evening resets the body clock to a later time.2 For eastward travel, this means waking up one hour earlier than usual and having exposure to bright light for at least one hour, with bedtimes also occurring one hour earlier than normal, adjusting by one hour daily starting three days before departure.5 For westward travel, travellers should seek light exposure in the evening by attempting to stay awake in bright indoor light until bedtime at the destination. While evidence on the effectiveness of light exposure has been mixed,3,6 it is an easy, low-cost and safe recommendation for all travellers.Melatonin has the most evidence of effectiveness on increasing sleep duration and improving sleep quality, with doses studied ranging from 0.5–10 mg, most commonly 5 mg at bedtime.7,8 Pharmacists should know that the dose-response curve for melatonin is relatively flat,2 so higher doses will not be more effective. The duration of therapy studied for jet lag has been up to five days, with one study showing benefit when taken for the first three days upon arrival and no benefit thereafter.9 In addition, melatonin is generally used for eastward travel only, since westward travel is easier to adapt to naturally, making melatonin unnecessary unless travel spans 12 or more time zones.10,11 One study reported immediate-release melatonin to be more effective than slow-release formulations.12 While melatonin is generally well tolerated, pharmacists should consider a traveller’s underlying risk of falls or use of other sedating medications and advise patients of the risks with use of any sedating product.Light exposure combined with melatonin administration has been found to have a somewhat synergistic effect.2Strategies to relieve symptomsWhile light and melatonin can be used to adjust the circadian rhythm, other interventions such as hypnotics, caffeine, napping and exercise can be used for symptom relief only. Of these, hypnotics (e.g., zopiclone) taken before bedtime upon arrival have the strongest evidence of effectiveness;3 however, these benefits must be weighed alongside risks of dizziness, confusion, residual morning drowsiness and falls, especially among older adults or those on other medications with sedating properties.Armodafinil (the R-enantiomer of modafinil, having a half-life of 12–14 hours vs. 3–4 hours for modafinil) has been studied in a randomized placebo-controlled trial of eastbound travellers crossing six time zones who had a history of jet lag symptoms from previous flights.13 This trial reported that average scores related to sleep latency over the first two days at the destination were better vs. placebo among those taking armodafinil at morning doses of either 50 mg or 150 mg; however, differences related to global severity measures of sleepiness were observed over the first two days only among those randomized to the 150 mg dose, with further analysis finding that this effect was limited to just the first day.13 Armodafinil is not currently marketed in Canada and its use for jet lag is off-label in the United States.14 Patients and prescribers may have questions about whether a similar effect can be expected from modafinil, which is currently unknown.Evidence for nonpharmacologic interventions is mixed;6 however, like light therapy, they are low risk and can be recommended as adjunctive measures:Caffeine: Caffeine intake through beverages or tablet form may improve daytime alertness and has been found to be more effective than melatonin at reducing objective sleepiness;15 however, intake later in the day or of higher amounts may contribute to difficulty falling and staying asleep at night.Napping: Naps of 20–50 minutes improve alertness; however, naps exceeding 30 minutes have been found to contribute to nighttime sleep inertia (temporary disorientation and decline in reaction time or cognitive function upon awakening).16Exercise: Evidence is mixed on the effect of exercise on jet lag; however, outdoor exercise during the day provides the added benefit of exposure to bright light. For eastward travel, exercise later in the evening may help advance sleep cycles.6Technology to support travellers in preventing and managing jet lagApps and web-based calculators have been developed to guide travellers on light exposure, melatonin, naps and caffeine use to prevent or manage jet lag, with Timeshifter among the most frequently used (Table 1).ConclusionJet lag is a common and frustrating occurrence among travellers, particularly for eastward travel. Pharmacists may be consulted on measures to prevent or manage jet lag before travel or upon return. Bright light therapy and melatonin can be used to shift the circadian rhythm, while other interventions may provide symptom relief. Travellers interested in trying melatonin should be educated that higher doses are not more beneficial, with 5 mg the most commonly studied.Sherilyn Houle is an assistant professor, School of Pharmacy, University of Waterloo, ON, and a pharmacist at the International Travel & Immunizations Clinic, Centre for Family Medicine in Kitchener, ON. She has her Certificate in Travel Health from the International Society of Travel Medicine.References:American Psychiatric Association: Diagnostic and statistical manual of mental disorders, Fifth edition, Text revision. Washington, DC, American Psychiatric Association, 2022.Sack RL. The pathophysiology of jet lag. Trav Med Infect Dis 2009;7(2):102-10.Herxheimer A. Jet lag. BMJ Clin Evid 2014;2014:2303.Eastman CI. High-intensity light for circadian adaptation to a 12-h shift of the sleep schedule. Am J Physiol 1992;263(2 Pt 2):R428-36.Eastman CI, Burgess HJ. How to travel the world without jet lag. 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