Jet Lag Planner
Behind the Recommendation
What the App Is Trying to Do
Jet lag occurs when your internal circadian phase (the “body clock”) is out of sync with the new local time. The fastest way to reduce symptoms is to shift the clock efficiently while avoiding timing mistakes that push it the wrong way. Our scheduler uses three main levers:
- Light (seek vs avoid)
- Melatonin (dose and timing)
- Exercise (being active)
All timings are derived from peer-reviewed phase-response curves (PRCs) to light and melatonin, with practical rules distilled from Roach & Sargent (2019)[1].
Key Physiology (Why Timing Matters)
- CBTmin (core body temperature minimum) is the circadian “pivot.” Light in the ~12 h before CBTmin induces phase delays, while light in the ~12 h after CBTmin induces phase advances. The largest shifts occur with light ~3–6 h either side of CBTmin (Czeisler et al., 1989[2];Khalsa et al., 2003[3]).
- Melatonin has its own PRC:Maximum advances occur when taken ~11.5 h before CBTmin (~6.5 h before habitual bedtime); maximum delays occur when taken ~4 h after CBTmin (~1 h after habitual wake). (Burgess et al., 2008[4])
How the App Generates Your Plan
- Estimate starting phase: CBTmin is approximated as ~2–3 h before habitual wake time.
- Compute target shift: Direction and magnitude of time zone change determine whether phase advances (eastward) or delays (westward) are scheduled.
- Map PRCs to actions:
- Light: Seek bright light in the appropriate PRC zone (advance vs delay) and avoid it in the opposite zone.
- Melatonin (optional): Scheduled near the PRC peak for the desired shift direction, avoiding dead zones.
- Exercise (optional): Scheduled near the PRC peak, placed to reinforce the desired shift.
- Apply constraints: Daily phase shifts are capped (~1–2 h/day), and travel demands are integrated.
Why These Specific Timings Work
Eastward travel: Morning light (post-CBTmin) plus evening melatonin accelerates advances and blocks delays.
Westward travel: Evening/night light (pre-CBTmin) plus morning light avoidance delay the clock efficiently. Melatonin may be used but is less critical.
Risks and Side Effects
Melatonin (3 mg immediate-release): Possible drowsiness, vivid dreams, headache, GI upset. May interact with anticoagulants, sedatives, antihypertensives, immunosuppressants. Not well studied in pregnancy, lactation, epilepsy, or autoimmune disease. Avoid activities requiring alertness if drowsy.
Light: Nighttime light can impair sleep if mistimed.
Sleep timing, naps, caffeine: Early-afternoon naps can reduce fatigue without harming night sleep. Caffeine aids alertness but does not shift the circadian phase.
Limitations
- CBTmin is estimated, not measured—individual variation can cause mismatches.
- PRC data are averages; responses vary by genetics, age, light history, season.
- Light intensity and exposure vary in real-world conditions (clouds, indoor light).
- Flight schedules and commitments can constrain optimal timing.
- Evidence is based on specific melatonin doses/forms (3 mg immediate-release).
- Not a medical device—consult a clinician for medical conditions.
Summary
Your personalized schedule is built by estimating your circadian phase (CBTmin), calculating the advance or delay required, and aligning light, melatonin, exercise and sleep to the most effective PRC zones while avoiding exposure that would counteract the shift. The underlying science is drawn from laboratory circadian studies and expert synthesis. Outcomes will vary between individuals.
References
- Roach GD, Sargent C. Interventions to Minimize Jet Lag After Westward and Eastward Flight. Front Physiol. 2019;10:927. Link
- Czeisler CA, et al. Bright light induction of strong (type 0) resetting of the human circadian pacemaker. Science. 1989;244(4910):1328–1333. Link
- Khalsa SB, et al. A phase response curve to single bright light pulses in human subjects. J Physiol. 2003;549(Pt 3):945–952. Link
- Burgess HJ, et al. Human phase response curves to three days of daily melatonin: 0.5 mg versus 3.0 mg. J Clin Endocrinol Metab. 2008;93(12):4655–4660. Link