Jet lag Survival Guide: Traveling 1-3 time zones eastward


Jet lag Survival Guide: Traveling 1-3 time zones eastward

It’s so difficult to help your child adjust to a socially normal bed and wake times at home, so the prospect of traveling across time zones with a baby or toddler can be daunting. We won’t say that adjustment to jet lag is easy, but your child’s circadian rhythm is designed to be flexible, and given time and careful control of light and darkness, your child can adjust to a trip across the country with little drama. Note that travel can be complicated beyond jet lag. For more tips and tricks, check out our travel survival guide here.

The Science

A quick warning about this science section; it’s complicated. We’ve tried to simplify it, but if you find your head spinning don’t worry. Many students of circadian biology have trouble with this topic in the beginning. You can just skip to the jet-lag plans below and follow them without knowing the science if needed.

Jet lag is so-called because with the invention of air travel humans became able to rapidly cross time zones faster than our internal body clock (or circadian rhythm) could keep up. The “lag” in jet-lag refers to the time that it takes for your circadian rhythm to catch up to socially normal bed/wake/eating times in a new time zone.

The circadian rhythm is flexible and makes small adjustments every day even when you stay in the same time zone because the circadian rhythm for about 70% of people is a little longer than 24 hours (about 30% have a circadian clock that runs a little shorter than 24 hours). This means that your child’s (and your) circadian rhythm has to make a small adjustment to the clock in order to keep biological time in synchrony with the 24-hour day. Think about it like this, your body clock is like a watch that runs about 12 minutes fast. Every morning when you wake up, you have to readjust the clock, so that it keeps accurate time.

How does the circadian rhythm reset? It happens through the timing of your daily light exposure through your eyes (your eyes have to be open for it to work). If you weren’t exposed to light in the morning, then your biological bedtime and wake time would start to drift later and later every day. Babies are not born in synch with the 24-hour day and if you plot your baby’s sleep from birth you may see this type of shifting pattern, where the longest sleep bout doesn’t stay at night. Similarly, some people who are totally blind aren’t able to synchronize and develop a disorder called non-24 sleep-wake disorder, where the circadian rhythm just keeps following its own clock and cannot be reset to social time.

When you travel across time zones the same adjustment process will happen, BUT since the timing of light exposure (sunrise, sunset) relative to your child’s body clock will be off, the timing of light exposure could actually make things much worse. Why? Because light at different times of day does different things. Light in the morning shifts sleep earlier, while light in the evening shifts everything later, but, of course, “morning” and “evening” are relative to your child’s body clock, NOT your watch. In addition, during the biological night, there is a transition point where light the effect of light reverses. The figure below illustrates this change.

Jet lag Survival Guide: Traveling 1-3 time zones eastward

This is why jet lag is hard. You have to think about what time it is in your child’s body and control light exposure relative to that time.

Finally, it’s important to know that the circadian rhythm is one of the two sleep drives (see basics on sleep here), but it also controls a great deal of other biological functions including hormone production, urine excretion, cognitive function and it also plays a role in meal timing. This means that when your child is jet lagged, it’s not just sleep that will be off – everything will be off.

Why is eastward jet lag so hard?

Eastward jet lag can be straightforward, but there are some common situations that complicate things when you travel eastward. This is best illustrated through example: Imagine that your child sleeps from 7:00 PM to 6:00 AM. If you are traveling westward, say from New York to Los Angeles, your child will need to be exposed to light in the evening, but you’ll need to keep it dark in the morning when you arrive in California. This is fairly easy to do, because the sun will be out later relative to your child’s internal clock and you’ll intuitively try to keep it dark and ask your child to sleep if she wakes at 3:00 AM in California (6:00 AM biological time).

When you travel eastward, it’s a bit more complicated. Morning light exposure will help your child's body make the shift, but only if that morning light exposure is AFTER the transition point in your child’s body (see the graph above). For example, if you wake your child up for the day at 6:00 AM New York time, that’s 3:00 AM biological time. Light exposure at that time could cause major trouble and shift your child’s drive to sleep in the wrong direction. Similarly, there is a strong drive to be awake right before your child’s biological bedtime, if you try to put him down at 7:00 PM New York time, that’s 4:00 PM LA time, which will basically end up leading to your child taking a nap and then being wide awake for several hours after. As you’ll see below, it’s best to start with your child’s biological bedtime/wake time and work away from that even if it’s a socially crazy bedtime or wake time.

You might think, “Why the heck would I wake my child at 6:00 AM when she’s able to sleep later?” That’s a great question and most parents never would wake their children early intentionally, but there are two common issues that cause waking at that odd hour. First, if you take a red-eye from the US West Coast, to the US East Coast, then it’s possible the disruption from travel and the plane landing will wake your child. This is obviously a problem because it will start your child off with light exposure at the wrong time. Even if you don’t take the red-eye your child could end up having an early waking if you don’t have curtains sufficient to black out the windows in the morn