Circadian Rhythm
circadian rhythm
A circadian rhythm is an approximately 24-hour biological cycle that governs the sleep-wake pattern, body temperature fluctuations, and hormone secretion in living organisms.
Social Jet Lag
social-jet-lag
Definition
Social jet lag is a concept introduced in 2006 by Till Roenneberg at Ludwig Maximilian University of Munich. It is quantified as the shift in mid-sleep point (the midpoint between falling asleep and waking) between workdays, when the schedule is dictated by social obligations, and free days, when the body's natural rhythm can take over. For example, someone who sleeps from midnight to 7:00 AM on weekdays (mid-sleep 3:30 AM) and from 1:00 AM to 10:00 AM on weekends (mid-sleep 5:30 AM) has two hours of social jet lag.
Health Risks
Studies report that the larger a person's social jet lag, the more it is associated with obesity (higher BMI), depressive symptoms, poorer cardiovascular markers, and lower academic performance. The weekly cycle of resetting the internal clock every weekend and then forcing it back to the social schedule on Monday is described as a burden similar to crossing time zones every week.
How to Reduce It
One individual strategy considered effective is to keep weekend wake-up times within one hour of the weekday alarm. While sleeping in on weekends can repay short-term sleep debt, it also pushes the circadian rhythm later, so relying on catch-up sleep alone is not advisable. At the organizational level, flexible working hours and staggered start times help accommodate the diversity of chronotypes among employees.
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Related Terms
Chronotype
chronotype
Chronotype refers to an individual's natural preference for the timing of sleep and activity, broadly classified as morning type, evening type, or intermediate type, and strongly influenced by genetic factors.
Jet Lag
jet-lag
A temporary sleep disorder caused by rapid travel across multiple time zones, disrupting the body's internal clock.
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