In the journals: Scientists discover how shift work may threaten health
To investigate the physiological effects of circadian misalignment, researchers at Boston's Brigham and Women's Hospital studied 10 healthy volunteers for 10 days in a laboratory free of time cues. The subjects were placed on a 28-hour day, each day beginning four hours later than the one before, until their sleep/wake cycles were reversed. Activities and meals were also carefully controlled. As a result, the volunteers slept and ate at all phases of their internal circadian cycles, or body clocks. The researchers took hourly measurements of glucose, insulin, cortisol (the so-called stress hormone), and leptin (an appetite-regulating hormone that sends fullness signals to the brain) and daily measurements of blood pressure, heart rate, and other functions, including brain wave activity during sleep.
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