Value Village ／ Health
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Jet lag is a shared complaint among international travellers, and the time difference between Japan and Europe or North America is 8–14 hours. The sleep guide published by Japan's Ministry of Health, Labour and Welfare (MHLW) takes the view that the body clock is moved by light and by meal times. Here we turn that idea into practical steps for a trip to or from Japan.
| Item | Details |
|---|---|
| Body clock cycle | Slightly longer than 24 hours (on average around 24 hours 10 minutes). Reset every day by morning light |
| Speed of adjustment | About 1–1.5 hours a day. Tokyo to London (8–9 hours' difference) takes several days to a week |
| Eastward (advancing the clock) vs westward (delaying it) | Eastward is harder (the body clock is better at delaying than advancing) |
| Using light | Get strong light in the local morning and avoid light in the local evening (sunglasses, dimmer screens) |
| Meals | Eating at the local breakfast time moves the peripheral body clocks |
| Naps | Early afternoon, 30 minutes or less. Long naps slow the adjustment |
[Verify] The speed of body-clock adjustment is a general statement from sleep medicine. Check the status of melatonin in Japan against MHLW documents.
What matters is matching your sleep to the destination's time; simply sleeping longer does not move the body clock. As a guide: if you land in the morning, sleep on the plane; if you land in the evening, stay awake on the plane.
A long nap, or a nap in the late afternoon or later, stops you sleeping in the local night and slows the adjustment. If you really must, early afternoon, 30 minutes or less.
Alcohol makes the second half of your sleep shallower and adds to dehydration. Combined with dry cabin air, it increases fatigue after arrival.
Starting 2–3 days before departure, moving bedtime and waking time one hour a day towards destination time works with the way the body clock behaves. It is generally described as most useful for eastward travel.
Adjustment tends to slow with age, but younger people are affected too. Do not schedule anything important on the first day of the trip — a practice shared among Japanese business travellers.
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https://www.mhlw.go.jp/content/10904750/001181265.pdf
https://www.e-healthnet.mhlw.go.jp/information/heart/k-02-002.html
https://www.mhlw.go.jp/stf/seisakunitsuite/bunya/kenkou_iryou/iyakuhin/yakubuturanyou/index.html
⚠️ Editorial note: the source URLs above were identified by search. Our working environment cannot reach go.jp domains, so the contents have not been checked against the text. Verify every source before publication and record who checked it and when.
What we share here are ideas and everyday practices passed down among people living in Japan, together with general information drawn from public sources. They are not official recommendations, and they are not professional instruction. Practices vary between households and regions.
This is general information. Results vary from person to person and depend on your own conditions and surroundings.
Please decide for yourself, using your own judgement, whether any of this suits your situation. We cannot accept responsibility for any damage, loss or injury arising from following this article.
This article is not meant to diagnose or manage any specific medical condition. If you are worried about your health, see a doctor rather than relying on your own judgement.
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