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Shedding Light on the Effect of Permanent Daylight Saving Time

By: , Posted on: May 11, 2022

The U.S. Senate recently passed a bill to establish Daylight Saving Time (DST) year-round. While the National Sleep Foundation agrees that the Senate’s decision to eliminate bi-annual clock changes is good for sleep and follows public sentiment, permanent Standard Time is a better fit for our natural sleep/wake process and our overall health and well-being.

Changing the clocks has had a contentious history over the last 50 years. It seems we’re always questioning the reasoning of the change as we trudge through the week following a clock reset. The appeal of having longer, brighter evenings, especially as summer nears makes permanent DST seem the “better” option. In reality, DST shifts total bright hours from when we need them in the morning to later in the afternoon. In many cities around the country, switching to permanent DST will delay sunrise. For example, the city of Indianapolis would experience sunrise at 9:06am in the morning at some points during the year. That means children and adults are going to school and work in the dark for multiple months of the year. In fact, in 1974, the United States experimented by switching to permanent DST in 1974 and quickly reverted to a bi-annual clock change later that same year.  The failed experiment had negative effects on health, safety, and performance.

DST essentially fights the natural order of our circadian rhythms, the natural sleep/wake process in our bodies. Our circadian rhythms rely on bright natural light in the morning to wake us up and to synchronize important biological processes, and dimmer light in the evening to make us sleepy and ready for bed. It’s unhealthy to alter our bodies’ sleep schedule to have more daylight hours in the evening.

A consistent year-round time system is agreed upon by NSF and other leading sleep and science-based organizations and NSF released a Position Statement on permanent Standard Time last year. Our sleep-wake cycle does not adjust to annual clock change, leading to negative effects on health and safety including cardiovascular disease, motor vehicle crashes, mood changes and depression, and metabolic abnormalities.

Foundations of Sleep Health™, the first textbook from the National Sleep Foundation (NSF) presents sleep as a critical element of overall individual and population health. This new book provides a historic and current perspective of the state of sleep. The Policy Environment chapter in Foundations of Sleep Health, written by Dr. Birkland, explains the nature and logistics of policy changes to better prioritize the sleep of the nation. As we’ve seen in the Senate recently, permanent DST or standard time must be undertaken solely at the federal level. Under the Standard Time Act of 1966 states may opt out of the observance of DST but they cannot opt into a permanent adoption of DST or standard time.

It’s important to know the facts around clock changes to help make informed decisions for you and your family’s health. The human circadian system does not adjust to annual clock changes. Sleep becomes disrupted, less efficient, and shortened. DST forces our biological clocks out of sync with the rising and setting of the sun (the sun clock). The link between our biological clock and the sun clock has been crucial to human health and well-being for millennia. Permanent Standard Time is a better fit for our circadian rhythms and the better choice for health and well-being.

Foundations of Sleep Health is available in the Elsevier Store.

Erin Koffel, PhD, LP, is the Senior Director of Research and Scientific Affairs at the National Sleep Foundation. Thomas A. Birkland, PhD, is a Professor of Public Policy in the School of Public and International Affairs at NC State University.

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