How it starts?
The sage of Philadelphia conceived of a system similar to daylight saving time in 1784 while serving as America’s first ambassador to France. In a letter to the editor of the Paris Journal, he estimated that the simple act of awakening at sunrise and retiring at sunset in the months between spring and fall would result in an annual saving of a little more than 64 million pounds in candle wax for Paris’s residents.
Further Studies illustrates:
Conserving energy has always been the object of daylight saving time, of course. Yet Matthew Kotchen, a professor of environmental economics at the University of California, Santa Barbara, and Laura Grant, a doctoral student, argued in a recent study that it may increase residential electricity demand.
They studied 7 million electric bills over three years in Indiana where for decades 77 counties chose to skip the spring ahead and fall behind. In 2006, the State Legislature ended the boycott, and the Hoosiers seem to have the last laugh. Against intuition and contrary to the entire point of government policy, the study found that daylight saving time resulted in an $8.6 million increase in spending on residential electricity.
But don’t count out Ben. Those Indiana residents used more power, but for heat and air conditioning — something far beyond the capabilities of 18th-century tallow. The researchers found that the power used for lighting declined significantly in every month but October. Mr. Franklin proposed ending the program on Sept. 20.
Mr. Franklin, brilliant as he was, hardly envisioned Nintendos and computers, big-screen televisions and dishwashers. He wanted, he wrote, the “pure light of the sun” to help him escape the “smokey, unwholesome and enormously expensive light of candles.”
He never took his idea too seriously. In the same letter he suggested that, if necessary, cannons be shot off at sunrise to ensure that laggards get out of bed, and described a friend’s insistence that opening the shutters to greet the dawn lets out the darkness rather than bringing in the light.
Adding more light, of course, makes many people feel better. At this time of year, the early sun that moved Franklin, and now makes my basil branch out from its pot on my kitchen window, is a sweet sign that late winter’s days are numbered. Maybe cannons are called for after all — to celebrate.
by MAURA J. CASEY (http://www.nytimes.com)Keeping in View:
A quarter of the world's population is subjected to a 1 hr time change twice a year (daylight saving time, DST). This reflects a change in social clocks, not environmental ones (e.g., dawn). The impact of DST is poorly understood. Circadian clocks use daylight to synchronize (entrain) to the organism's environment. Entrainment is so exact that humans adjust to the east-west progression of dawn within a given time zone. In a large survey (n = 55,000), we show that the timing of sleep on free days follows the seasonal progression of dawn under standard time, but not under DST. In a second study, we analyzed the timing of sleep and activity for 8 weeks around each DST transition in 50 subjects who were chronotyped (analyzed for their individual phase of entrainment). Both parameters readily adjust to the release from DST in autumn but the timing of activity does not adjust to the DST imposition in spring, especially in late chronotypes. Our data indicate that the human circadian system does not adjust to DST and that its seasonal adaptation to the changing photoperiods is disrupted by the introduction of summer time. This disruption may extend to other aspects of seasonal biology in humans.
Major Health Issues:
Daylight saving time, which began this week in most of the United States, has long been promoted as a way to save energy. Whether it does is still a matter of debate. But it does seem clear from studies that a one-hour time adjustment can have unintended health consequences.
It seems that when the clock is moved forward or back one hour, the body’s internal clock — its circadian rhythm, which uses daylight to stay in tune with its environment — does not adjust. In a study of 55,000 people, for example, scientists found that on days off from work, subjects tended to sleep on standard time, not daylight time: their waking hour followed the seasonal progression of dawn.
In other studies, scientists tracked large groups of people for eight weeks at a time as they made the transitions to daylight time in spring and to standard time in autumn. They found that in spring, people’s peak activity levels were more in tune with their body clock than with the actual clock. Studies suggest that this disconnect between body time and clock time can result in restlessness, sleep disruption and shorter sleep duration. Other studies have suggested links between time change and increases in heart attacks, suicides and accidents, though scientists say more study is needed.
THE BOTTOM LINE
Daylight saving time is associated with sleep disruptions and possibly more serious consequences.
No comments:
Post a Comment