Anyone who has travelled long distances knows the debilitating
effects jet lag can have on one’s body and mind.
Not only can crossing time zones leave a person tired
during the day or wide awake at night, it can cause irritability,
fatigue, difficulty focusing, impaired judgement, decreased
productivity, and memory lapses. And it’s not just because of
poor sleep on the plane and dehydration from the altitude—the
feelings persist for several days.
Jet lag is caused by our 24-hour body clock lagging behind
the rapid change of clock time over the flight. The body clock
consists of our circadian rhythms and has a strong effect on the
times across the day we feel alert and when we feel sleepy.
Once the body clock becomes stabilized, it is resistant to
change. So, after less than a day in the air, our body clock is still
on home time when we arrive at our destination. This is where
the problem arises.
Flying east can present a challenging re-adjustment. It takes
longer to reset or re-entrain the circadian clock following
eastward than westward flight.1
Take the example of flying from New York to Paris. At this
time of year, there is a six hour time zone difference between the
two cities. If you arrive in Paris at 7:00 a.m. in the morning, your
body clock will be telling you it is 1:00 a.m.
If you manage to stay awake across the next six hours, you
will then find it easier to stay awake for the next 16 when your
body clock thinks it’s time for sleep, but that will be 5:00 a.m.
Paris time, with an expected wake-up time at 1:00–2:00 p.m.
having missed half the day. Until you can shift the timing of
your body clock earlier by about five or six hours, your jet lag will
continue to cause extreme tiredness in the late morning and
difficulty getting to sleep at night.
Re-timing your body clock
The good news is you can re-time your body clock using light
devices such as Re-Timer. Scheduled exposure to bright light
can alleviate the symptoms of jet lag by accelerating circadian
re-entrainment to new time zones.2
But take care to get the timing right so you move your body
clock in the right direction. Light stimulation after your body
reaches its lowest body temperature (Tmin), usually about two
hours after your typical wake-up time, will shift your body clock
to an earlier time. However, light before your Tmin will shift your
body clock later.
For a New York to Paris trip, you would need to advance
(or shift earlier) your body clock by about six hours to most
completely align your body clock to Paris time.
It would be useful to use Re-Timer in the morning from
8:00 am, shifting earlier each day by 30 minutes until you get to
your preferred wake-up time to complete the jet lag cure.
Take the example of flying back from Paris to New York. If you
arrive in New York at 7:00 a.m., your body clock will be telling
you it is 1:00 p.m. (six hours later than it is in Paris).
If you manage to stay awake until early evening, you will still
be woken up early the next morning by your early-timed body
clock and early “wake-up zone,” making you feel tired the next
day. In New York, your Tmin from the Paris adjustment will now
be occurring at about 10:00 p.m.. Until you can shift the timing
of your body clock later by about five or six hours, your jet lag
will continue to cause extreme tiredness in the late afternoon
and early (3:00–4:00 a.m.) awakenings without sufficient sleep.
Re-timing your body clock
For the Paris to New York return trip, you will need to delay your
body clock by about six hours to most quickly align your body
clock to New York time. In this case, it would be useful to use
Re-Timer in the later evening to complete the jet lag cure.
How to beat jet lag
One way to reduce the time taken to overcome jet lag in your
destination is to do some re-adjustment of your sleep period
and light exposure before leaving on your trip. Jet lag calculators
can work out the specific times for your light exposure before
and after the trip.
But should you even attempt to re-time your body clock?
That depends on how long you’re staying in the new time zone.
If your stay is short (one or two days), it may be less disruptive
to not go through any re-adjustment, but simply keep your body
clock on “home” time. That way you also avoid re-adjusting
again when flying home. Most airline flight crew follow this rule.
But if your stay overseas is going to be more than a few days
and if you want it to be more pleasurable, you can minimize jet
lag with Re-Timer and appropriately timed light stimulation.
About Re-Timer light therapy
Re-Timer is the world’s first wearable green-blue light therapy
device designed to re-time the circadian rhythm. Worn like a
pair of glasses, the device shines green-blue light into the user’s
eyes, altering a person’s circadian rhythm and helping to adjust
his or her body clock to a new time zone. This color of light has
been shown by university research to be the most effective color
for re-timing the body clock and is UV free. Using the device for
30–50 minutes a day can help people overcome sleep issues
based on circadian rhythm mis-timing including insomnia,
winter blues and jet lag.
The Re-Timer glasses retail for $299 and can be purchased at www.re-timer.com.
- Eastman CI, Burgess HJ. How To Travel the World Without Jet Lag. Sleep Med Clin. 2010;4:241–55.
- Boulos Z, Campbell SS, Lewy AJ, Terman M, Dijk DJ, Eastman CI. Light treatment for sleep disorders: consensus report. VII. Jet lag. J Biol Rhythms. 1995;10:167–76.