Stanford study: Ending daylight saving time could improve American health

The Impact of Daylight Saving Time on Health

Changing the clocks twice a year is an annual ritual that many people dread. However, a recent study conducted by sleep researchers at Stanford Medicine suggests that this practice could have significant health consequences. The research highlights the potential benefits of eliminating daylight saving time (DST) and adopting either permanent standard time or permanent DST.

The study found that switching to permanent standard time could lead to a reduction in several health issues. Specifically, it estimated that 2.6 million fewer people would be diagnosed with obesity, and approximately 300,000 fewer stroke cases would occur annually. Even if the country were to adopt permanent DST, which means not turning the clocks back in November, the benefits would still be substantial—roughly two-thirds of those seen with permanent standard time.

Key Findings from the Study

The research, published in the Proceedings of the National Academy of Sciences, analyzed data from the Centers for Disease Control and Prevention (CDC) and used the latest circadian models to assess the impact of different time policies on public health. Lead author Lara Weed, a graduate student in bioengineering, emphasized that the study focused on the effects of time changes on circadian rhythms, which are crucial for regulating sleep and other bodily functions.

Dr. Jamie Zeitzer, a senior author and professor of psychiatry and behavioral sciences, noted that the current system of changing clocks twice a year is less beneficial compared to maintaining either standard time or DST permanently. He explained that frequent time changes disrupt the body's natural rhythms, leading to various health issues.

Historical Context and Current Debates

Permanent daylight saving time has been attempted before, but it did not yield positive results. For instance, a bill proposed by Florida Republican Senator Rick Scott aims to make DST permanent through the Sunshine Protection Act. Scott argued that the biannual clock changes are an unnecessary inconvenience for families.

On the other hand, the National Sleep Foundation has advocated for making standard time permanent. They argue that DST interferes with the body's natural circadian rhythms, which rely on bright morning light to regulate sleep-wake cycles. According to the foundation, altering these rhythms can lead to negative health outcomes.

Weed and Zeitzer acknowledged that their study does not account for all factors, such as economic and safety considerations. The models assumed consistent sleep habits and outdoor hours, which may not reflect real-world conditions. Zeitzer pointed out that even in places like California, where the weather is favorable, people spend less than 5% of their day outside, which could affect the accuracy of the findings.

Understanding Circadian Rhythms

Circadian rhythms are biological processes that follow a roughly 24-hour cycle, influencing when we feel sleepy and alert. These rhythms are regulated by exposure to sunlight and darkness. Morning light helps reset the internal clock, while evening light can delay the release of melatonin, a hormone that promotes sleep.

Disruptions to circadian rhythms, such as those caused by DST, can lead to sleep deprivation, which is linked to various health problems, including heart disease, cognitive decline, and obesity. Additionally, circadian rhythms influence other bodily functions, such as heart rate, blood pressure, stress hormones, and metabolism.

Upcoming Clock Change

The next time the clocks will change is on November 2, 2025, when people will "fall back" at 2 a.m. This adjustment marks the end of daylight saving time and the return to standard time.

As the debate over daylight saving time continues, the findings from this study provide valuable insights into the potential health benefits of adopting a more stable time policy. Whether it’s moving to Hawaii or Arizona, or simply eliminating the biannual clock changes, the goal remains clear: to support better health and well-being for all.