What is social jetlag?

Wednesday, August 26, 2020

This holiday period may see fewer of us taking to the skies and therefore not experiencing the jetlag that comes with long-haul travel. However, there is another type of jetlag, social jetlag, which you can experience even if holidaying closer to home.


What is social jetlag?

Social jetlag[1] occurs when our daily activities are not in sync with our natural biological rhythm of activity during the day and sleep at night. It also occurs whenever sleep doesn’t follow a regular night-time pattern. Travelling across different time zones is one cause – there are many other causes.

For example, waking up early to care for young children, working shifts that start early one week and late the next, eating late or watching movies late at night, or a combination of all these factors can cause social jetlag.


Examples of causes of social jetlag in modern society

  • Early shift start time
  • Exercise schedule
  • Hectic social life
  • Late shift finish time
  • Night shift work
  • Long work hours
  • Long commutes
  • Childcare responsibilities at night
  • Eating at unusual times
  • Domestic responsibilities

Jetlag, and social jetlag, both interfere with our ideal biological timing of sleep at night and being awake during the day. After arriving at a destination with a new time zone, and for example, when working night shifts, for multiple days we can have trouble sleeping, feel tired during the day, feel hungry in the middle of the night and want to eat during the day. In addition, we feel moody, irritable and lack motivation.


People working ‘9 to 5’ can experience social jetlag

About 20% of the population in industrialised countries are shiftworkers, and regularly work outside the typical ‘9 to 5’ work schedule. Shiftwork is obviously a key cause of social jetlag, but people working standard office hours can also suffer from social jetlag.

From Monday to Friday, people working ‘typical hours’ tend to set an alarm to wake up ‘early’ in order to get to work on time. On the weekend they go to sleep later, for example after an evening out, and wake up later too. The timing of sleep during the week can often be very different from the weekend and is part of the reason why it can be difficult to adjust on Mondays.

Over time changing sleep times is associated with poor health. ‘Night owls’ or people who prefer going to bed late, are particularly prone to social jetlag. Night-owls naturally stay up late and easily accumulate a sleep debt during the work or school week, and to recover on the weekend they find it easy to wake late in the day, which makes it all the more difficult to go to sleep ‘early’ on Sunday night in preparation for the working week ahead.


What are the adverse consequences of social jetlag for sleep health?

Waking up and falling asleep within one hour of the same time every day is one of the hallmarks of good sleep health2. Frequent changes of more than about an hour in the timing of the sleep causes fatigue, bad mood, disrupted sleep, and increased ill-health. Social jetlag is also associated with reduced physical activity, increased likelihood of smoking and a higher incidence of obesity2


Is catching up on sleep on days off bad for sleep health?

Catching up on sleep on free days is necessary and encouraged. However, because the ‘regularity’ of sleep times is key to good sleep health, try to keep regular bed and wake up times on work and free days. If you do need to recover on the weekend or free days, try and sleep close to your ideal sleep time. For example, if your ideal sleep time is 10 pm to 6 am, try and sleep from 9pm to 7am.


Why is social jetlag so common?

It is estimated that 87% of people experience social jetlag3,4. Social jetlag is common because there are so many features of our modern lives that disrupt the timing of our sleep and body clock. The body clock is an area in the brain that ensures that all of our physiology, including respiration, metabolism, cardiovascular activity and sleep, follow 24-hour circadian rhythms (from Latin: circa = about, dia = day). The purpose of these rhythms is to prepare our bodies for activity during the day and sleep at night. The timing of the body clock is influenced by when we are exposed to light, which before the invention of the electric lightbulb, was just sunlight.

Many of us spend most of our time indoors exposed to artificial light rather than sunlight. When the sun goes down, we switch on an electric light to extend our day and can spend hours on light-emitting devices such as smartphones and computers in the evening. This pattern of light exposure enables us to extend the day, meaning many people are awake for around 17 hours and have an eating window (time between the first and last bite of the day) of around 15 hours. Light exposure, when we eat our meals and when we exercise all tell our body it is time to be awake, and extending our day in this way promotes social jetlag.


What are the different types of social jetlag?

Researchers have suggested that, as social jetlag is something we all experience at one time or another, modern society has essentially turned all of us into a type of shiftworker4. What type of shiftworker are you?

Lifestyle shiftworker

If, for example, you are a student (stay up late to prepare for assignments and exams), a musician, a new parent, you watch live sport on the television at night, or you are caring for an ill friend or relative.

Second-hand shiftworker

If you are living with a shiftworker.

Extended hours shiftworker

If you work long hours or leave very early in the morning and return home very late at night because you need to travel long distances to get to work. Adding long travel times to even a ‘9 to 5’ schedule can create extended work hours.

Digital shiftworker

If you stay up late into the night to chat to family and friends living in different time zones, or you are simply on social networks until late at night.


How to limit social jetlag

If you work ‘9 to 5’

We can all improve the regularity of our bed and wake-up times by adjusting our lifestyle and sleep habits. Evidence suggests that a few tweaks in your day and night routine (e.g. when you are exposed to light when you eat, your sleep routine) can help you be less of an evening person and adjust to ‘9 to 5’.

If you work shifts or extended day hours

Try, as much as possible, to build some regularity in sleep patterns around your work schedule. This requires a bit of planning and very much depends on the type of work schedule you work.


To summarise

We have all experienced social jetlag because our modern lifestyle has many ways of disrupting the timing of our sleep and our body clock. As social jetlag impacts our health over time, it is important that we identify and address sources of social jetlag.

You can watch this video on social jetlag and its consequences.



References1 - Roenneberg, T. (2012). Internal time: Chronotypes, social jet lag, and why you’re so tired. Harvard University Press.
2 - Buysse, D. J. (2014). Sleep health: Can we define it? Does it matter? Sleep, 37(1), 9-17.
3 - Roenneberg, T., Allebrandt, K. V., Merrow, M., & Vetter, C. (2012). Social jetlag and obesity. Current Biology, 22(10), 939-943.
4 - Panda, S. (2018). The Circadian Code: Lose weight, supercharge your energy and sleep well every night. Random House.