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 difference between wake-up time on workdays (dictated by social obligations) and wake-up time on free days (following the body's natural rhythm). For example, a person who wakes at 7:00 AM on weekdays but 10:00 AM on weekends experiences three hours of social jet lag.
Health Risks
Epidemiological studies have linked social jet lag of two hours or more to increased risk of obesity (higher BMI), depressive symptoms, elevated cardiovascular risk, 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 imposes a physiological burden equivalent to crossing time zones every week.
How to Reduce It
The most effective individual strategy 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 disrupts the circadian rhythm and is counterproductive over the long run. 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 largely determined by genetics.
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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