Every year, millions of people around the world move their clocks forward or back for Daylight Saving Time (DST). While the point is to maximize daylight, this practice often disrupts our circadian rhythms and can lead to a temporary misalignment between our internal clocks and our external environment. This year, clocks change on Oct. 26 in Europe and Nov. 2 in many US states. We spoke with our resident sleep expert, Dr. Teofilo Lee-Chiong, to explore how these time shifts impact your sleep, and share practical tips to help you adjust smoothly.
Q: Why does changing the clocks affect sleep at all?
Dr. Teofilo Lee-Chiong: Even small shifts in your sleep schedule - like the hour-long change associated with DST - can disrupt your sleep timing, reduce your sleep duration, and impair how rested you feel. In fact, abrupt changes in light exposure delay sleep onset and suppress melatonin release (that’s the hormone that signals your body that it’s time to sleep), impacting your sleep for days after the clocks change. This means that even minor changes, like an hour, can have measurable effects on your sleep!
Q: Is one time change harder than the other?
Dr. Lee-Chiong: It really depends on the person. Most people find “springing forward”, when Daylight Saving Time begins and we lose an hour of sleep, more challenging because it disrupts sleep and makes mornings feel earlier. However, some find falling back, when we gain an hour as DST ends, disorienting due to the earlier evening darkness. Research shows that the spring shift is more likely to cause sleep loss, mood changes and slower reaction times compared to the fall transition.1
Q: What are your top tips for adjusting more smoothly?
Q: What if I’m still feeling off days later?
Dr. Lee-Chiong: If you’re still struggling to fall asleep or feel alert after 5-7 days, you’re not alone! It could simply mean that you need more time to adjust or more support. That said, disrupted sleep can lead to mood issues, fatigue, and even immune or metabolic changes. If you’ve made the right changes to your routine and are still struggling, talk to your doctor or a sleep specialist; their guidance can make a big difference!
Q: So what’s the bottom line?
Dr. Lee-Chiong: The clock might change overnight, but your body needs more time. Be patient. A few days of grogginess or restless sleep are normal, but with the right steps, your internal rhythm will reset. My advice? Think of the time change as a perfect opportunity to reset your entire sleep routine: better light habits, less screen time before bed, and a more consistent schedule.
Dr. Teofilo Lee-Chiong is a highly-trained sleep medicine specialist, Prof. of Medicine at the University of Colorado Denver School of Medicine and Tenured Prof. of Medicine at National Jewish Health in Denver, Colorado. Dr. Lee-Chiong is the author of several books focused on sleep medicine.