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Part of Arizona could go to permanent Daylight Saving Time, against advice of health experts

A clock technician adjusts the hands on a large outdoor clock under construction at Electric Time Company in Medfield, Mass, last year, just days before daylight saving time was set to end.
Steven Senne
A clock technician adjusts the hands on a large outdoor clock under construction at Electric Time Company in Medfield, Mass, last year, just days before daylight saving time was set to end.

The U.S. Senate has unanimously approved a bill to switch most of the country to permanent Daylight Saving Time. If it’s passed by the House of Representatives and signed into law, the Navajo Nation would switch to Daylight Saving while the rest of Arizona would remain on Standard Time. Scientists say the decision has consequences for public health. KNAU’s Melissa Sevigny spoke with Dr. Seema Khosla, medical director of the North Dakota Center for Sleep and spokesperson for the American Academy of Sleep Medicine, which advocates for Standard Time year-round.

If this bill was passed, most of the country including the Navajo Nation in Arizona would go to permanent Daylight Saving Time, and that would mean there would be darker mornings and longer afternoons, is that right?

Right, right. The sun is in the sky the same amount of time regardless of what our clock says. The sun doesn’t care about what our clock says. We’re basically borrowing that hour of the sunlight from the morning and plunking it to the end of our day. It would be interesting to see what the vote would have done if it had taken place in November. We psychologically marry these two, we marry the idea of “spring forward” with more daylight, and days are getting longer, and the nights are getting shorter. But then if we march it out to what that means in the fall, for a lot of our country, we will not see sunrise until 9 o’clock in the morning. That can be really dangerous for our kids getting on the school bus.

Tell me more about that, what does this decision have to with human health?

When we talk about circadian rhythm, that’s our biological schedule for when we should wake up and when we should fall asleep. The greatest, what we call “zeitgeber,” which is a word that tells us this is the greatest influence, is sunlight. When we have Daylight Savings Time, we are about an hour off our own circadian rhythm…. So then it’s lighter in the evening, it makes it hardest to sleep, but then we also miss that light in the morning that helps us to wake up. People argue, that, well, people will adjust to this. They did a study on Germany and looked at what happens during Daylight Saving Time, and what they found is that on average people sleep about 30 minutes less every night. And so it’s not as simple as just getting used to it.

Thirty minutes less, that doesn’t sound like a huge amount of sleep. What does that do to our bodies?

If we look at the data on delayed school start times, for example, the American Academy of Pediatrics, the American Academy of Sleep Medicine, they all are in agreement that for middle school and high school, school should start no earlier than 8:30 in the morning…. What they found, by allowing the school to start later—everybody argued, the kids are just going to stay up, they’re not going to get more sleep, and the kids did stay up later, but they did get more sleep, and it was about, depending on the study, it was about half hour, 45 minutes, an hour—but what they found was kids performed better academically, there were fewer car accidents, less high risk activity, including drug use and alcohol use, just from getting a little bit more sleep…. You know, there are interactive websites where you can see what time sunrise is going to be in different parts of the country, like at Winter Solstice. On the easternmost part of the time zone, it’s different than the westernmost part of the time zone. And if you look at the data on cancer risk and heart disease and so on and so forth, there is a gradient across one time zone. There are profound implications. Our circadian rhythms, it’s so hard wired in every cell of our body, we can’t not consider that when we’re making these big decisions.

Dr. Khosla, thank you so much for speaking with me.

Thank you for having me.

Melissa joined KNAU's team in 2015 to report on science, health, and the environment. Her work has appeared nationally on NPR and been featured on Science Friday. She grew up in Tucson, Arizona, where she fell in love with the ecology and geology of the Sonoran desert.