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Tuesday, August 12, 2025

Jet lag


Definition

Jet lag, or desynchronosis, is a temporary circadian rhythm disorder caused by rapid travel across multiple time zones, leading to a misalignment between the body’s internal biological clock and the new local time. It is characterized by sleep disturbances, daytime fatigue, impaired cognitive function, and gastrointestinal upset.

Epidemiology

  • More common when traveling eastward than westward due to the body’s preference for longer (>24-hour) days.

  • Severity increases with the number of time zones crossed, especially beyond three.

  • All age groups can be affected, though older adults may experience longer recovery times.

Pathophysiology

  • The body’s circadian rhythm, controlled by the suprachiasmatic nucleus (SCN) in the hypothalamus, regulates sleep-wake cycles, hormone release, body temperature, and digestion.

  • Rapid travel across time zones disrupts the relationship between the internal clock and environmental cues (light-dark cycles, social activity, meal timing).

  • Melatonin secretion patterns become misaligned, affecting sleep initiation and quality.

Risk Factors

  • Greater number of time zones crossed.

  • Eastward travel (advancing the clock) is harder to adapt to than westward travel (delaying the clock).

  • Frequent travel without adequate recovery time.

  • Poor sleep quality before travel.

Clinical Features

Sleep-Related Symptoms

  • Difficulty falling asleep or staying asleep.

  • Early morning awakening.

  • Reduced total sleep time and quality.

Daytime Symptoms

  • Fatigue, drowsiness.

  • Decreased concentration and memory.

  • Mood disturbances (irritability, anxiety).

Other Symptoms

  • Gastrointestinal upset (constipation, diarrhea).

  • Appetite changes.

  • General malaise.

Diagnosis

  • Clinical diagnosis based on symptom onset after travel across time zones.

  • No specific laboratory tests are required.

  • Differentiate from travel fatigue (caused by dehydration, cabin pressure changes, immobility) which resolves quickly without circadian disruption.

Management

Non-Pharmacological Strategies

1. Pre-Travel Adjustments

  • Gradually shift sleep and meal times toward the destination’s schedule 2–3 days before travel.

  • Eastward travel: Go to bed and wake up earlier.

  • Westward travel: Go to bed and wake up later.

2. Light Exposure

  • Light is the most potent cue for resetting circadian rhythms.

  • For eastward travel: Seek morning sunlight exposure at the destination.

  • For westward travel: Seek late afternoon/evening sunlight exposure.

  • Avoid bright light at inappropriate times (e.g., wear sunglasses if exposure would delay adaptation).

3. Sleep Hygiene

  • Maintain a consistent bedtime and wake time at the destination.

  • Avoid caffeine, alcohol, and heavy meals close to bedtime.

  • Ensure a dark, quiet, and cool sleeping environment.

4. Hydration and Nutrition

  • Drink adequate water before, during, and after travel.

  • Avoid excessive caffeine and alcohol during flights.

  • Eat meals at local times to help entrain digestion.

Pharmacological Management

1. Melatonin

  • Useful for eastward travel and for helping realign circadian rhythms.

  • Dose: 0.5–5 mg orally, taken 30–60 minutes before intended bedtime at the destination.

  • Use for 2–5 nights after arrival.

  • Lower doses (0.5–1 mg) may be sufficient for circadian shifting, while higher doses (3–5 mg) aid in sleep induction.

2. Short-Acting Hypnotics (for severe sleep disruption, short-term use only)

  • Zolpidem: 5–10 mg orally at bedtime (max 10 mg/day; lower dose in elderly or women).

  • Zopiclone: 3.75–7.5 mg orally at bedtime.

  • Temazepam: 10–20 mg orally at bedtime (avoid in elderly due to fall risk).

3. Caffeine

  • Low to moderate doses (50–200 mg) can improve alertness in the daytime but should be avoided within 6–8 hours of intended bedtime.

Prognosis

  • Symptoms typically resolve within 1–2 days per time zone crossed.

  • Westward travel often has quicker recovery than eastward.

  • Adherence to light exposure, sleep hygiene, and gradual schedule adjustment can significantly shorten recovery.

Patient Education

  • Jet lag is temporary and improves as the body adjusts to the new local time.

  • Preemptive light exposure planning and melatonin use can help.

  • Maintaining hydration and avoiding alcohol excess during travel can reduce severity.




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