Social Jetlag: When Your Alarm Clock and Body Clock Disagree
If you get up with an alarm during the week and sleep in at the weekend, your sleep shifts back and forth every week. Research calls this gap social jetlag. The calculator shows how large it is for you.
On workdays
On free days, without an alarm
The calculator applies the formula from chronobiology to your answers. It does not replace a validated questionnaire or a diagnosis.
What social jetlag is
Munich chronobiologists coined the term in 2006. It describes the gap between social time, meaning work and school, and biological time. [1] It is measured as the distance between the midpoint of your sleep on workdays and on free days.
Worked example: Someone sleeps from 23:30 to 6:30 on five workdays and from 1:00 to 10:00 at the weekend. The midpoint of sleep is 3:00 on workdays and 5:30 at the weekend. The social jetlag is two and a half hours: as if the person flew two and a half time zones west every Friday and back on Monday. The calculator above starts with these values.
Who is affected most
Night owls. Their sleep times on workdays and free days are furthest apart: during the week they build up sleep debt, at the weekend they catch up. [1] [2] Only extreme early types show hardly any difference. [2] The chronotype calculator shows where you sit.
What research knows about the consequences
In a survey of 501 people, late chronotypes smoked considerably more often. Links with wellbeing and with caffeine, nicotine and alcohol consumption were strongest in teenagers and young adults up to 25. The authors attribute this mainly to social jetlag, not to chronotype itself. [1]
A large epidemiological study found in 2012 that social jetlag is associated with a higher body mass index, beyond sleep duration. [3]
Both are associations from surveys. They do not show that social jetlag alone is the cause.
What Circadian shows
Circadian does not calculate a value for social jetlag of its own. In the sleep review, however, you see every night over 14 or 30 days: when you fell asleep and when you woke up, with the days of the week below. If your sleep shifts at weekends, you see it as a jump in the lines. The overview also shows your typical sleep time and how far individual nights deviate from it on average.
What reduces the gap
Less sleep debt during the week, so there is less to catch up at the weekend. And light: people who spend more time outdoors in daylight sleep earlier [2], and bright light in the morning moves the body clock earlier. [4] The authors of the 2006 study also recommend adapting work and school times to chronotype where possible. [1]
Sources
- Wittmann M, Dinich J, Merrow M, Roenneberg T (2006). Social jetlag: misalignment of biological and social time. Chronobiology International 23(1–2):497–509.
- Roenneberg T, Wirz-Justice A, Merrow M (2003). Life between clocks: daily temporal patterns of human chronotypes. Journal of Biological Rhythms 18(1):80–90.
- Roenneberg T, Allebrandt KV, Merrow M, Vetter C (2012). Social jetlag and obesity. Current Biology 22(10):939–943.
- Khalsa SBS, Jewett ME, Cajochen C, Czeisler CA (2003). A phase response curve to single bright light pulses in human subjects. Journal of Physiology 549(3):945–952.
This article is for general information only and does not replace medical advice. Consult your doctor for health-related questions.
See how your sleep shifts across the week.
Circadian shows every night individually from your Apple Health data and estimates your energy across the day.
- Chronotype suggestion from six weeks of sleep data
- Sleep review over 14 or 30 days, night by night
- Energy curve from sleep and other Health data
- One-time purchase, no subscription and no account; analysis happens only on your devices
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