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Sleep Well in Seattle 1 – natural light

Seattle skyline

If, like us, you’ll be travelling to the Flight Safety Foundation’s International Air Safety Summit next week, look out for Senior Researcher Dr. Cristina Ruscitto’s jet lag tips throughout this week ahead of the conference.

We’ll be publishing Cristina’s advice in a series of blogs to help you mitigate the effects of jet lag and keep your body and mind in optimum condition for the conference next week.

What is jet lag?

You experience jet lag when you travel across multiple time zones and your body clock is out of sync with the time at your new destination. This means that you may eat, sleep and be required to focus and be alert at a time when you would normally be asleep in your home time zone. This gap between behaviours (influenced by the body clock) and local time increases as the number of time zones crossed increases making jet lag worse.

The most common symptom of jet lag is daytime fatigue/sleepiness associated with loss of concentration and motivation due to sleep loss. Sleep loss occurs as a result of trying to sleep to local time but being unable to do so as the body clock adapts slowly to a sudden shift in the 24-hour light/dark cycle. On average, it takes approximately 1 – 1.5 days recovery for each time zone crossed. Therefore, jet lag is a temporary condition for occasional travellers and it’s likely that jet lag symptoms will disappear within a few days as you adapt to local time. For example, following an 8-hour time change, recovery may take 8-12 days. However, as you may be in Seattle for only three to four days if you’re attending the IASS conference, it’s likely that you will experience some jet lag symptoms as your body is in the process of adapting to local time.

To help you cope with jet lag and maintain your alertness levels at the conference, we’ve put together a few tips for you which we’ll share  with you over the course of this week.

 Making the most of our jet lag tips

Our tips fall into two main categories. Help with:

1) Speeding up adaptation to local time to reduce the impact of jet lag symptoms:

  • By light (Read more on this in today’s blog)
  • By mealtimes (look out for Wednesday’s blog)

2) Coping with jet lag symptoms with sleep and alertness promoting strategies (See our blog on Thursday)

On Friday, we will conclude our jet lag blog with some reflections and suggestions on how to readapt to the home time zone.

It’s worth noting that adapting to local time may be more appropriate for longer trips (e.g. 4 days or more). If you are in Seattle for 2-3 days it may be advisable not to adapt  in order to prevent feeling jet lagged when you are back home. In this case the advice would be to manage your sleep and work out when you need to be alert for the conference. Check our blog on Thursday for advice on this.

Extra advice and practical help will be on hand from Research Director, Dr Alexandra Holmes at the Clockwork/Baines Simmons stand #28. If you’re feeling the effects of jet lag why not take some time out at the conference to come and recharge in our Energy Pod!

Woman waking up in the morning

1. Speeding up adaptation to local time

Introducing the 1st of our tips: When to catch and avoid bright light

It is useful to start matching your behaviour (when you are active, eat and sleep) to local time before you travel (set your watch). However, this may not always be possible due to a busy home lifestyle.

Nevertheless, following arrival in Seattle, the best advice is to adopt behaviours that match the local time as soon as possible. Light is the most important synchroniser for our body clock and the trick is knowing when to get light exposure. Evidence suggests that large shifts in body clock timing (and therefore faster adaptation) occur around the time that your body temperature is at its lowest (temperature minimum) – on average this is about two hours before you wake up. Exposure to natural light before the temperature minimum will push your clock later in time (required for westwards travel, e.g. London-Seattle) whereas light after your temperature minimum will bring your clock earlier in time (required when flying eastwards, e.g. Sydney-Seattle) (Revell & Eastman, 2005). Knowing when to avoid light is also important part of shifting the body clock to the desired direction. Here are some tips according to the direction of your travel:

 Eastward travel (e.g. Sydney-Seattle)

On average it is more difficult to adjust to a shorter day when you fly east but if your choice is to adapt to Seattle time, catch plenty of natural bright light during the biological day (day in the home time zone) to shift your clock earlier and avoid bright light exposure during the biological night (night in the home time zone) and wear a mask or blue-light blocking glasses until after you normally wake up in the home time zone. As the body clock shifts slowly, exposure to light can be moved by 1-2 hours during subsequent days.

 Westward travel (e.g. London-Seattle)

Light resets the body clock and keeps it synchronised to 24 hours. However, because our body clock has a tendency to shift to a later time (e.g. 24.5 h) in the absence of time cues, most people find westward travel much easier to cope with than eastward travel as it is consistent with our natural tendency to delay sleep. Bright light before biological night (night in the home time zone) will help you shift your clock to later times by about an hour per day.

How bright does light need to be?

Lux (illuminance) is a measure of how much light falls onto a certain area. Research has shown that Indoor light (minimum 50 lux) is enough to generate a shift in the body clock. However, in terms of bright light, natural daylight (10000-25000 lux) is three times more effective than artificial light (variation between fluorescent and LED light) at shifting our body clock. Furthermore, research has found that the body clock responds to blue light more than any other colour and even dim blue light (approximately 8 lux) can have an impact. Therefore blue light can be used to shift the body clock more efficiently, particularly when it is cold and not as bright outside in winter days.

Conversely, it is advisable to avoid the use of electronic devices if you are avoiding light strategically to shift your body clock. The alternative would be to limit blue light exposure by wearing blue-light blocking glasses and applying screen filters. Some devices have night mode settings for example.

 Man sleeping on a plane

Are you a lark or an owl?

It is important to note that there are individual differences in sleep times which means the timing of the temperature minimum is likely to vary. Sleep times are influenced by your body clock type: being a lark or an owl. If you would like to find out more about your body clock type, you can take a test online by clicking on the link below to find out what body clock type you are (The Morningness-Eveningness Questionnaire): http://www.cet-surveys.com/index.php?sid=34172&newtest=Y

The table below offers an indication of wake up times associated with your body clock. Whilst lifestyle can get in the way of your preferred sleep times, evidence suggests that typically, evening-type ‘owls’ have sleep patterns timed 2-3 hours later than morning-type ‘larks’.

Definite Evening Moderate Evening Intermediate Moderate Definite Morning
Sleep onset 2:00-3:00 AM 12:45-2:00 AM 10:45 PM-12:45 AM 9:30-10:45 PM 9:00-9:30 PM
Wake up 10:00-11:30 AM 8:30-10:00 AM 6:30-8:30 AM


5:00-6:30 AM 4:00-5:00 AM


(Morningness-Eveningness Questionnaire, MEQ-SA, at www.cet.org)

Why is useful to know more about wake up times?

If you have regular sleep times at home, it is easier to estimate your temperature minimum (approximately 2 hours before wake up) and know when to be exposed to bright light to influence the direction of your body clock (earlier or later in timing) in the new time zone. If you have travelled from the west, you will want to delay your sleep times to adapt to Seattle time so bright light exposure should occur before the temperature minimum. Conversely, if you have travelled from the east, you should get as much bright light after the temperature minimum to bring your body clock earlier in time.

In theory, larks have an advantage in adapting to eastward travel (e.g. Sydney-Seattle) as their body clock timing is naturally early in the day. On the other hand, owls are better at travelling to the west (e.g. London-Seattle) as they have a tendency to go to bed later. However a limitation is that the majority of people have an ‘intermediate’ body clock type, therefore it is likely that more extreme types will benefit from their tendency to delay or advance their sleep.

Follow us on Linkedin or Twitter to receive our daily jet lag advice tips throughout this week and if you’d like to arrange a time for a chat at the IASS conference, please email info@clockworkresearch.com.


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Ruscitto, C., & Ogden, J. (2016). The impact of an implementation intention to improve mealtimes and reduce jet lag in long-haul cabin crew. Psychology & Health, 32(1), 61-77.

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