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End of Daylight Saving Time Can Have Mental, Physical Effects

Jupiterimages/Thinkstock(MUNICH, Germany) -- The end of Daylight Saving Time -- scheduled for Sunday, Nov. 6 this year -- may make people groan and complain as the sun begins to set earlier and late afternoons grow dark, but researchers say that the return to natural rhythms can be healthy.

"The circadian clock does not change to the social change," said chronobiology researcher Till Roenneberg of Ludwig Maximilans University in Munich, Germany.  "During the winter, there is a beautiful tracking of dawn in human sleep behavior, which is completely and immediately interrupted when Daylight Saving Time is introduced in March."

Roenneberg, lead researcher for a study of the effects of time shifts, said that humans' biological clocks are stronger than the clocks set by Congress.

"When you change clocks to Daylight Saving Time, you don't change anything related to sun time," Roenneberg said.  "This is one of those human arrogances -- that we can do whatever we want as long as we are disciplined.  We forget that there is a biological clock that is as old as living organisms, a clock that cannot be fooled.  The pure social change of time cannot fool the clock."

Though individuals may see their biological clocks reset, and will get an "extra hour" of sleep or rest over the weekend, researchers say that the stress caused by time changes can be bad for the body.

Researchers in Sweden published a report in 2008 in the New England Journal of Medicine reporting that the number of heart attacks jumps during the period immediately following time changes, and that those vulnerable to sleep deprivation should be extra careful.

"More than 1.5 billion men and women are exposed to the transitions involved in Daylight Saving Time: turning clocks forward by an hour in the spring and backward by an hour in the autumn," wrote Imre Janszky and Rickard Ljung, health and welfare researchers in Sweden.  "These transitions can disrupt chronobiologic rhythms and influence the duration and quality of sleep, and the effect lasts for several days after the shifts."

Janszky and Ljung said that sleep deprivation can affect the cardiovascular system, leading the vulnerable to have heart problems in the days following Daylight Saving Time changes.

Copyright 2011 ABC News Radio

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