Social jet lag: need a smoke?

Science News,  August 5, 2006  by Janet Raloff

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People who have a hard time waking in the morning because their bodies' internal clocks are out of syne with their sleep schedules are said to have "social jet lag" Researchers in Europe have determined that the phenomenon strongly correlates with smoking.

Battling one's biological clock can leave people weary in the same way as traveling across several time zones can, says Till Roenneberg of Ludwig-Maximilian University in Munich. Roenneberg's team developed a questionnaire to determine when a person's internal clock is genetically set to have him or her to sleep or be awake. The researchers then gave the questionnaire to some 40,000 people to collect details about their sleeping schedules.

The team determined that more than half the study participants routinely go to bed at least 2 hours later or wake at least 2 hours earlier than the times set by their biological clocks.

The scientists then administered follow-up lifestyle questionnaires to 500 participants. People with significant social jet lag were at least three times as likely to be smokers as were people who didn't experience the sleeping problem. Some 30 percent of people experiencing 2 hours of social jet lag daily were smokers, and the smoking rate spiked to 60 percent in people typically living at least 4 hours out of sync with their bodies' clocks.

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