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AAN 2024 | Effect of daylight savings time on sleep
In this interview, Karin Johnson, MD, University of Massachusetts Chan Medical School-Baystate, Springfield, MA, discusses the negative effect of daylight savings time on sleep due to our circadian rhythms not adjusting to the time change and remaining aligned with the rising and setting of the sun. Difficulty falling asleep coupled with an earlier wake time leads to reduced sleep duration and quality, and this increases the risk of chronic disease, decreases alertness and cognition, and heightens the risk of events such as injuries and car crashes. Prof. Johnson emphasizes that public health policies can make a significant difference in the quality of life of individuals who are at high risk of sleep deprivation. For example, later school start times can allow adolescents to sleep longer and improve their academic performance, as well as reduce their risk of drug usage and mental illness. This interview took place at the American Academy of Neurology (AAN) Annual Meeting 2024 in Denver, CO.
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Transcript
We have time zones, and that’s really what sets our social schedule; when we go to work, when we go to school. If we’re on standard time zone, they are meant to sort of align with the sun being overhead at noon. Unfortunately, when we’re on daylight savings time, everything shifts by an hour, so sunrises and sunsets are later. But, our bodies follow the sun. Our circadian rhythms stay more aligned with the sun time...
We have time zones, and that’s really what sets our social schedule; when we go to work, when we go to school. If we’re on standard time zone, they are meant to sort of align with the sun being overhead at noon. Unfortunately, when we’re on daylight savings time, everything shifts by an hour, so sunrises and sunsets are later. But, our bodies follow the sun. Our circadian rhythms stay more aligned with the sun time. So what happens is we have even a harder time falling asleep at night, yet our work and school has been moved an hour earlier, and so we really kind of squish the opportunity that we have to get adequate sleep.
We also see when we’re more circadian misaligned, we get poorer quality sleep. That affects not only what we just talked about of sort of chronic disease prevention, but affects our alertness, our cognition, we see that people don’t do as well in school, are more likely to get injured, more likely to get into car accidents. It’s a little counterintuitive. A lot of people think if it’s light later, you know, we’ll be safer. We won’t get in a car accident, but we actually see the opposite because the brain is really important. If we’re being more sleep-deprived or having that circadian misalignment, it really isn’t good for any aspect of our lives.
We have a lot of good studies from looking at position in time zone; people that live in the western edge of the time zone, where the sun rises and sun sets later, we see higher risks of obesity and heart disease, cancer, again, things like worse outcomes on SAT scores, more fatal car accidents. So, we have growing data in that. Then we have studies that show that public policy can make a difference. So, the later school start time movement that just gives kids that opportunity to potentially get a half hour to an hour more sleep, are making them do better in school, show up more at school, be less likely to do drugs, have less mental health problems. These public health policies really can help the most at risk people, which are anyone that is a teenager and has that natural delayed rhythm, or anyone that has a work or school start time before 8 a.m., which is the majority of the population, and often those who are sort of already at most risk categories for being sleep deprived in the first place.
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