From Munich, at the Euroscience Open Forum meeting
People who have a hard time waking in the morning because their bodies' internal clocks are out of sync 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.