This year, Daylight Saving Time will start one week later than usual, in November instead of before Halloween. Did you notice it didn't get quite so dark this year when it was time for trick or treaters?
I have written in the past about how Daylight Saving Time interferes with our internal connection with the earth and nature, and now there is scientific evidence to support it.
I heard on National Public Radio's Day to Day program this morning a conversation about a new study showing that our internal clocks are thrown into whack during the entire period of Daylight Saving Time.
The story is also on US News and World Report's website. Some highlights from the German study, in the October 24 edition of Current Biology:
In the study, Roenneberg's group collected data on the sleep patterns of 55,000 people in Central Europe. The researchers found that sleep time on days off work when daylight savings time took effect followed the seasonal progression of dawn under standard time, but not under daylight savings time.
In a another study, Roenneberg's group looked at the timing of sleep and activity for eight weeks during the change to daylight savings time in 50 people, taking into account each person's natural clock preferences, or "chronotypes," which range from morning larks to night owls.
For both morning larks and night owls, their timing for sleep and peak activity easily adjusted when daylight savings time ended in the fall. However, it never adjusted to the return to daylight savings time in spring. This was especially true for night owls -- those who stay up late and sleep late.
"If we didn't change to daylight savings time, people would adjust to dawn during the summer and again to dawn in the autumn," Roenneberg. "But this natural adjustment is interrupted by daylight savings time," he said.
People's circadian rhythm -- the body's internal clock -- follows the sun and changes depending on where you live. It actually changes in four-minute intervals, exactly the time it takes for the sun to cross one line of longitude, Roenneberg explained.
"The circadian clock does not change to the social change," Roenneberg said. "During the winter, there is a beautiful tracking of dawn in human sleep behavior, which is completely and immediately interrupted when daylight savings time is introduced in March," he said. It returns to normal this year when standard time returns on Nov. 4, he added.
Daylight savings time may be one cause of what Roenneberg called our lack of seasonality. By seasonality, he means that our internal clock is in tune with the natural change in light throughout the year. "This could have long-term effects," he said.
