On March 12, nearly every state in the United States will “spring forward” from standard time to daylight saving time, or DST. (Hawaii and most of Arizona don’t observe DST.) That switch shifts an hour of light from the morning to the evening. For many people, it means losing an hour of sleep and trying to rise before the sun. Our bodies don’t like it. And they may be telling us something important, science now suggests.
Twice each year, the scheduled clock changes — to daylight saving time each spring, and back to standard time each fall — wreak havoc on sleep and schedules.
Actually, the name “daylight saving time” isn’t quite right, says Kenneth Wright. He’s a sleep and body-clock expert at the University of Colorado Boulder. There’s no change in the amount of daylight, he says. “What we’re doing is changing how we live relative to the sun.” When we move clocks forward an hour, noon no longer represents when the sun is near its highest point in the sky. Suddenly, people’s schedules are out of sync with the sun.
Biologically, Wright says, that’s a big deal. Humans evolved with a daily cycle of light and dark. It sets our body’s internal clock. And that, in turn, directs the rhythms of our bodies, from when we sleep and wake to when hormones are released. Morning’s blue light, in particular, is a key wake-up signal. When we tinker with time (or light), he says, “we’re essentially making the choice: Do we want to go with what we’ve evolved with, or do we want to alter that?”
What if he had to rank permanent daylight saving time, permanent standard time or our current practice of switching twice a year? From a health perspective, Wright says, “I think the…
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