Jet lag: what the evidence says actually helps

You land after a long flight, the local clock says it's morning, and your body insists it's the middle of the night. That mismatch has a name. The US Centers for Disease Control and Prevention (CDC) describes jet lag as a sleep disorder caused by rapid travel across time zones, which temporarily puts your internal biological clock out of step with local time. Its diagnostic criteria require crossing at least two time zones.

The good news: it passes. According to the NHS, jet lag usually improves within a few days as your body adjusts. The better news: you can shorten it.

What jet lag feels like

The NHS lists difficulty sleeping at bedtime and waking up in the morning, tiredness, difficulty staying awake during the day, poor sleep quality, and problems with concentration and memory. Some people also get indigestion, nausea, constipation, appetite changes or mild anxiety.

Why flying east is harder

Your internal clock doesn't run on exactly 24 hours. The CDC explains that its average cycle is slightly longer than 24 hours, so it is easier to stretch your day (flying west) than to shorten it (flying east).

The CDC gives these typical adjustment rates:

Two examples from the Gulf

• Doha to Tokyo is six hours east (neither city changes its clocks for summer). At about one hour a day, full adjustment can take around six days.
• Doha to New York is seven hours west while the US is on daylight saving time, and eight hours in winter. At about 1.5 hours a day, that is roughly five days.

These are averages, not promises. They explain why the first days of an eastbound trip are usually the hardest.

Before you fly

• Shift your sleep in advance. The CDC says moving your sleep one hour later per day (for westward travel) or one hour earlier (for eastward travel) during the two to three days before your trip may reduce the time needed to adjust.
• Arrive rested. The NHS advises getting enough rest before you travel. Starting a trip already short of sleep makes everything worse.
• Staying less than two days? The CDC suggests not adapting at all on short trips: keep your sleep, activity and meals on your home time zone.

On the plane

The NHS recommends:

• drinking plenty of water, since the CDC notes that dehydration can worsen the physical symptoms;
• keeping active by stretching and walking around the cabin;
• trying to sleep if it's night-time at your destination, with an eye mask and earplugs;
• not drinking too much caffeine or alcohol, which can make jet lag worse.

After you land

Use light on purpose

Light is the strongest signal your body clock receives. The CDC explains that morning light moves your clock earlier and evening light moves it later. So after flying east, get outside in the morning; after flying west, get daylight in the late afternoon and evening. The NHS gives the same practical advice: go outside during the day, because natural light helps your body clock adjust.

For a schedule built around your exact flight, the CDC mentions jet lag calculators that suggest when to seek and avoid light.

Switch to local time straight away

The NHS advises changing your sleep routine to local time as soon as you arrive and setting an alarm in the morning so you don't sleep in.

Keep naps short

The NHS advises against sleeping during daylight hours. If you really can't stay awake, the CDC says a short nap of 20 to 30 minutes can help alertness, while longer daytime naps can interfere with your sleep that night.

Caffeine, with a cut-off

The CDC suggests that caffeine can help daytime alertness, for example 200 mg every four hours during the day, and that you stop six hours before bedtime.

Go easy on alcohol

Alcohol may help you fall asleep, but the CDC notes that it tends to break up your sleep later in the night.

What about melatonin?

This is where official advice differs, so it is worth reading both sides.

• The CDC says taking melatonin at the right time can help shift your body clock: in the early evening of your body's time to help after flying east, and in the morning of your body's time after flying west. It says 0.5 to 1 mg is often enough and advises against high doses (above 5 mg), which can leave melatonin in your system at the wrong time of day. It also warns that in the US melatonin is not regulated by the Food and Drug Administration, so the amount in a tablet may differ from the label.
• The NHS does not recommend melatonin for jet lag, because there is not enough evidence to show it works.

Rules on selling melatonin also differ from country to country. In some it is sold over the counter; in others it needs a prescription. If you are considering it, ask a pharmacist or doctor first.

Sleeping pills

The NHS says medicines are not usually needed for jet lag. Sleeping tablets can help with severe sleep problems for a short time, but they can be addictive. The CDC advises avoiding antihistamines and long-acting sleeping medicines, which can worsen thinking and reaction times and increase the risk of falls. Any sleep medicine should be discussed with a doctor.

A short plan you can follow

1. Two to three days before: move bedtime one hour a day toward destination time.
2. On the plane: water, movement, sleep only if it's night where you're going.
3. On arrival: local time for meals and sleep, daylight at the right time of day, naps no longer than 30 minutes.
4. First evenings: no caffeine in the six hours before bed, little or no alcohol.