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If you woke up before your alarm went off this morning, it's no big surprise. Those of us who turned back our clocks over the weekend are still adjusting. NPR's Allison Aubrey reports that scientists are learning just how sensitive our bodies are to time.
ALLISON AUBREY, BYLINE: When we turn back the clocks in the fall or spring forward in the spring, the one-hour change may not seem like a big deal, but our bodies definitely notice. Daylight saving time is actually linked to an increased risk of traffic accidents, heart attacks and strokes.
JAY CHUDOW: It is definitely a surprise when thinking about one-hour difference causing significant health effects.
AUBREY: That's Jay Chudow. He's an internal medicine resident at Montefiore Health System. He says the bad effects that have been documented in studies are mostly linked to the spring forward change when we lose an hour of sleep. And he was curious to know how that might influence the risk of a heart condition known as atrial fibrillation or AFib. It's a type of irregular heartbeat. So he analyzed about 6,000 hospital admissions over an eight-year period.
CHUDOW: What we found when we took a look at people who were admitted to the hospital for atrial fibrillation was that linked to daylight saving time, there was a 20-percent increase in the number of admissions for atrial fibrillation in the days following spring transition. And it was surprising.
AUBREY: Chudow is set to present his research at an American Heart Association conference this week. The findings are preliminary, but they give insight into just how sensitive our bodies can be to time. Fred Turek is director of the Center for Sleep & Circadian Biology at Northwestern University. I asked him what's happening in our bodies and brains as we adjust to the time change.
FRED TUREK: You might think that one-hour time change is not a lot. But it turns out that the master circadian clock in our brain is pretty hardwired. It runs with a period of about 24 hours, and it's synchronized to the light-dark cycle.
AUBREY: And daylight is a primary cue to reset the clock. So if daylight comes an hour earlier or later, it throws us off.
TUREK: So all of a sudden, if you change the day by an hour, that internal clock has to catch up. It's going to take a day or two for it to readjust to the new time.
AUBREY: Turek says over the last 20 years, scientists have learned a lot about how our body clocks help regulate our biology. And it's not just the master clock in our brain. We have time-keeping mechanisms in every organ of the body. And increasingly, there's evidence that when our habits - such as when we eat and sleep - are out of sync with our internal clocks, it can harm us. Our bodies crave consistent routines. So when we disrupt them by, say, binge-watching late-night TV or midnight snacking or doing overnight shift work, there can be consequences.
TUREK: There's a great deal of research studies demonstrating that when we shift the biological clock and we shift the sleep-wake cycle - if that's done on a chronic basis, it leads to disease states such as obesity, diabetes and cardiovascular disease.
AUBREY: It doesn't happen overnight, but the risks increase the more your habits are at odds with your natural rhythms. At this time of year, as the amount of daylight continues to decrease, it can be easy to fall into bad habits. Psychologist Sanam Hafeez says especially in northern climates where it's cold and dark people are inclined to hibernate.
SANAM HAFEEZ: So that daylight change can actually really throw off a lot of things, including socialization, emotional rhythm. It sort of has a pervasive effect on some folks.
AUBREY: To combat the dark-day blues, Hafeez has three basic pointers. One, plan social gatherings in advance. Maybe join a club or a group linked to a hobby. Two, watch your alcohol consumption since drinking too much can amplify the pervasive effects. And three, go to bed an hour or so earlier so you can get up and maximize that exposure to sunlight in the morning hours. Allison Aubrey, NPR News.