Why early means surly

By Alison Motluk in Miami Beach PEOPLE who wake early feel more stressed during the day than those who like to sleep in, researchers in London have found. Angela Clow and her colleagues at the University of Westminster asked 42 volunteers to take saliva samples eight times during the day for two days. They took the first sample as soon as they woke up. Waking times ranged from 5.22 to 10.37 am. Analysis of the saliva from the half who woke earlier—before 7.21 am—showed they had higher levels of cortisol, the body’s main stress hormone, than those who woke later. Their cortisol levels remained high all day. Differences in the average number of hours asleep for the two groups could not account for this. The researchers hope to discover whether high cortisol levels caused the early birds to wake early, or whether their hormone levels were high because of their early start. Chronic stress is associated with depression and suppressed immunity. In a 10-week follow-up study, Clow found that early risers reported more muscle aches, cold symptoms and headaches—and significantly worse moods. More on these topics:
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