Daylight Saving Time (DST) has been in use in the United States since 1918. It was first implemented as a wartime measure to save energy during World War I. Since then, various sleep medicine experts and organizations have advocated to discontinue DST in favor of Permanent Standard Time. The new presidential administration has also called for an end to DST.
Proponents of DST argue that people prefer more daylight hours after the typical “9 to 5” workday.1 Supporters have also argued that DST decreases energy consumption by reducing the need for lighting and heating, but the actual effect on overall energy use is disputed.2
Supporters of ending DST point to the disruption in circadian rhythms.3 Light is the most powerful exogenous zeitgeber, or cue, to the regulation of the endogenous circadian rhythm. The typical sleep-wake cycle relies on bright light exposure in the morning and its absence in the evening. Standard time is thought to align more closely with natural circadian rhythms. It does this by offering more sunlight in the morning, promoting wakefulness and alertness. Evenings gradually become dark earlier, promoting a decrease in wakefulness. This alignment supports more consistent sleep patterns. With DST, evening light exposure is prolonged. When exposed to light in the evening or denied of light in the morning, the circadian clock responds by delaying phases, which can disrupt sleep patterns.
Societal effects are numerous. Fatal car crashes temporarily jump in the first few days after the springtime change, according to a study of US traffic fatalities. The risk is highest in the morning, and researchers attribute it to sleep deprivation.
Several health effects have been described. The American Heart Association points to studies that suggest an increase in heart attacks on the Monday after DST begins and in strokes for two days afterward. It should be noted that it is already known that heart attacks are more common on Monday mornings. According to a study of hospital admissions across the state of Michigan, there was a 24% increase in heart attacks on the Monday following the switch to DST. The number of people hospitalized with atrial fibrillation increased in the days following the springtime change, according to a 2020 analysis of admissions at Montefiore Medical Center in New York. In a study from Finland, researchers found that the overall rate of ischemic stroke was 8% higher during the first two days after a DST transition.
The American Academy of Sleep Medicine holds the position that “seasonal time changes should be abolished in favor of a fixed, national, year-round standard time.”3 Its position was endorsed by 20 other organizations, including the American College of Chest Physicians, National Safety Council, and National PTA.4
Whether the efforts of supporters of ending DST will bear results remains to be seen.
References
1. Mikkelson D. Daylight Saving Time. Snopes. March 13, 2016.
2. Yuhas A. When Is Daylight Saving Time?. The New York Times. March 6, 2024.
3. Rishi MA, Ahmed O, Perez JHB, et al. Daylight saving time: an American Academy of Sleep Medicine position statement. J Clin Sleep Med. 2020;16(10):1781-1784.
4. American Academy of Sleep Medicine calls for elimination of daylight saving time. American Academy of Sleep Medicine. August 27, 2020. https://aasm.org/american-academy-of-sleep-medicine-calls-for-elimination-of-daylight-saving-time/