Chapter 16 - Jet Lag

Learning Outcomes

After reading through this chapter, you should be able to:

  • Describe why long-distance travel causes jet lag.
  • Explain why travelling east can produce more jet lag than travelling west.
  • Provide practical strategies to ease the effects of jet lag.

Jet Lag

Jet lag is a condition caused when we travel across time zones, and our normal circadian rhythms are disrupted. It is experienced in the form of physical and psychological discomfort. The symptoms may include excessive sleepiness, feeling depressed, reduced efficiency, and premature awakening. Some people also experience this for the first day or two following the change to daylight saving time, when bed and wakeup time is shifted by an hour. Since daylight saving time only displaces our body clocks by an hour, the effects are likely to be minimal. Likewise, crossing only one or two time zones is not likely to produce substantial effects of jet lag.

The determining factor in the impact and experience of jet lag is how many time zones are crossed. Since time zones change only when travelling in east or west directions, north-south flights produce far less jet lag. For example, flying from Vancouver to Montreal (three hours difference) will produce substantial jet lag. However, a traveller on a north-south flight of the same duration – Vancouver to Los Angeles, for example – will not be affected by jet lag, only fatigue resulting from travelling.

Jet lag and the body clock

The body clock has already been discussed in Chapter 1 in terms of the effects of shift work and trying to sleep during the day. While circadian irregularities are fundamentally the same for international travel, there are two main differences between shift work and jet lag:

  • the time zone change associated with jet lag is preceded by the fatiguing activity of travel
  • the day/night environment surrounding sleep will have changed (i.e., become earlier or later), which confuses the body clock
  • although the new “night” sleep actually occurs during the local nighttime when it is dark, it may still be daytime at home and thus not a normal sleep time

Effects of jet lag

It is easier to move our sleep and waking time forward rather than backward, making the day longer rather than shorter. Eastbound travel shortens the day or night, so travelling west produces less jet lag.

You are more likely to be effected by jet lag by flying east because:

  • depending on the distance travelled, you lose several hours of sleep time
  • your body clock will only partially reset when changing time zones. The body clock takes an average of one day to adjust for each time zone crossed. A difference of four hours between home and local time may take you up to four days to adjust.

The impact and experience of jet lag varies dramatically between individuals. How you are affected depends on many factors, including:

  • direction of travel (travelling west is easier)
  • physical fitness (better fitness improves circadian adjustment)
  • age (the effects of jet lag increase with age)

One of the most common symptoms of jet lag is sleep disruption. This is likely to include:

  • difficulty getting to sleep at regular bedtime
  • waking up during the night and not being able to get back to sleep
  • fighting sleep during the day

This level of sleep disruption is likely to lead to insufficient sleep quality and quantity, and subsequent fatigue.

In 1994, a survey was conducted of international flight attendants in New Zealand. Almost all flight attendants surveyed said that despite being accustomed to international travel, they regularly suffered from jet lag. One of the particular symptoms reported by the flight attendants following a long flight was a sensation of confusion or “fuzziness.” For example, some flight crew members reported checking to make sure their hotel rooms were locked two or three times.

Easing the effects of jet lag

The most obvious technique for minimizing the effects of jet lag is maximizing sleep quality and quantity. Methods vary between individuals. Three useful tips are recommended:

  • set up your sleeping environment to minimize light and noise disturbance, and set the temperature to between 18 and 24°C
  • drink lots of water
  • keep physically fit

Resetting the body clock is more easily accomplished gradually than all at once. Depending on the direction you have travelled, and how long you plan on staying at the destination, one option is to start adjusting sleep and eating times before you leave. Even shifting your bed and meal times by an hour or two can jumpstart the change in your body clock in the right direction.

Ensure you are well rested before the flight. Many travellers are tempted to stay up late, and get very little sleep before a flight so they will be able to sleep better upon arrival at their location. In reality, people who are already in sleep debt before a flight will experience more symptoms than those who are well rested. Other than sleep, one of the easiest and most practical techniques to ease the effects of jet lag is to drink plenty of water. Dehydration and the dry air aboard aircraft can cause headaches and nasal irritation, which exacerbate the symptoms associated with jet lag. Drink lots of water before, during, and after the flight. Some tips to remember are:

  • take a large bottle of water with you on the flight – water is better than coffee, tea, soft drinks, and fruit juices
  • avoid coffee and alcohol, which are diuretics and cause dehydration
  • avoid overeating (especially salty foods)
  • avoid motion sickness drugs when possible (they are depressants).

Regular exercise also has a large impact on the severity of jet lag. People who are unfit tend to experience longer periods of jet lag.

Regardless of your actual fitness, being forced to remain immobile is one of the most taxing aspects of long flights. Move around and exercise wherever possible, throughout the flight or during stopovers. Don’t worry what other people think. If you look like you’re enjoying yourself, they may get up and join in.



Have you ever experienced jet lag? Describe your experience.


What techniques do you use to cope with jet lag?


Based on what you have just read about jet lag, are there any changes you should think about making? If so, what?



checkmark Knowledge Check

  • Explain what causes jet lag.
  • Identify two factors that can affect the experience of jet lag.
  • Explain two ways to ease the negative effects of jet lag.
Date modified: