How Changing Clocks Disrupts Sleep and Health

Learn why daylight saving time began, how it disrupts our bodies, and what we can do about it.
Valeriya I.'s avatar
Dec 17, 2024
How Changing Clocks Disrupts Sleep and Health

Picture a Monday morning in March. You wake up groggy and disoriented after losing an hour of sleep the night before. Twice a year, many of us set our clocks forward or back to follow daylight saving time. This routine was meant to save energy and make better use of daylight. Yet few of us realize the real cost. These clock shifts can upset our sleep, harm our bodies, and weigh on our minds.

How the Clock Got Its Makeover

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Law text for the world's first nationwide DST switch (Reichsgesetzblatt, German Empire, 1916.

Daylight saving time first appeared during World War I, when Germany and Austria-Hungary moved their clocks forward on April 30, 1916. They hoped to save coal and work more efficiently by using extra daylight. Britain, France, and the United States soon followed. By taking advantage of the sun, these nations cut their need for artificial lighting and saved valuable resources.

After both World Wars, rules for changing the clocks varied widely. In the United States, every state — and sometimes each county — sets its own schedule, causing confusion in travel and business. To bring order, Congress passed the Uniform Time Act of 1966. This law set a national standard, yet allowed states to opt out if they wished.

Other countries also sought to simplify things. Over time, most adopted a shared daylight saving season running from spring through fall. Today, about 70 countries still change their clocks. Some never bother. Others keep shifting twice a year. This patchwork of policies often puzzles travelers and businesses trying to keep on schedule.

How Shifting the Clock Throws Your Body Offbeat

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Infographic of a conventional circadian rhythm. Credit: News Medical Life and Science.

Your body has its own clock that keeps track of when you should be awake and when you should sleep. This “internal clock” depends on light and darkness to stay in sync with the world around you. When the clock on your wall changes by an hour, your body’s clock can’t adjust right away. You may feel tired, find it hard to pay attention, and have trouble sleeping at the proper time. In other words, you feel as if you have jet lag — without even leaving your home.

The Hidden Damage of Losing Sleep

Sleep Duration Reduction: After the start of Daylight Saving Time, one study found that people lost about half an hour of sleep on the first night. At the same time, the number of those who said they slept poorly rose sharply, jumping from around 2% to nearly 14%.

Lingering Effects: The same study showed that this tired feeling sticks around. Before the clock changed, nearly half felt rested when they woke up. After it, that number fell to about 40% and stayed low for several days. This means folks not only lose sleep right away, but they also stay more tired for a while.

Increased Daytime Sleepiness: Another study, which looked at teenagers, showed a similar pattern. Once DST kicked in, teens slept about 32 minutes less each school night. Over the week, that added up to almost three hours of lost sleep. As a result, they felt more groggy and had trouble paying attention during the day.

Losing even an hour of rest makes a difference. In the days after a time change, people often sleep less and feel more irritable. They have trouble thinking clearly, and their moods suffer. These changes show up at work and school, lowering our productivity and performance.

Risks to Physical Health

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Average fatal crashes for DST switches (USA). Credit: CarInsurance.org

Cardiovascular Events: Hospitals report a 24% increase in heart attack visits on the Monday after clocks spring forward. Disrupted sleep has been linked to higher risks of heart disease due to changes in blood pressure and inflammation levels.

Accidents: A 6% increase in car accidents has been observed immediately after the time change, attributed to reduced alertness and increased fatigue among drivers.

Long-term Effects: Chronic circadian misalignment may lead to more severe health problems such as obesity, diabetes, and even certain cancers due to ongoing disruptions in metabolic processes.

Where the Battle Over Clock Changes Is Heading

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Vitalik Buterin about DST. Credit: @VitalikButerin X’ account.

High-profile figures such as Senator Marco Rubio and former President Donald Trump have propelled the push to end biannual clock shifts. Rubio introduced the “Sunshine Protection Act” to make Daylight Saving Time permanent, arguing that longer evening light benefits businesses and families, while Trump’s offhand endorsement on social media drew sudden attention. States like Florida, Washington, California, and Oregon passed their own pro-DST bills but await federal approval.

Many TV hosts and comedians, including Jimmy Kimmel and Stephen Colbert, lampoon the disruption caused by jumping an hour forward or back. Sports enthusiasts and retail advocates claim extra daylight promotes outdoor recreation and boosts economic activity, while the American Academy of Sleep Medicine and other health experts favor permanent standard time, citing the benefits of morning light for physical and mental well-being. Influential entrepreneurs and online communities add their voices, either supporting year-round DST or echoing doctors’ concerns about disrupted sleep cycles.

Despite widespread debate and multiple petitions, lawmakers have yet to settle on one fixed schedule. Whether the United States adopts permanent DST, permanent standard time, or continues switching twice a year depends on reconciling public demand for lighter evenings with scientific calls to honor our natural circadian rhythms.

timezone calculators
Credit: Forbes

Facing the Issue and Finding Tools

If clock changes persist, small habits can help: adjust your bedtime in advance, embrace morning light, and keep a regular routine. Technology can lend a hand as well. World Clock Master makes it easier to coordinate meetings and events across time zones, easing at least one burden of shifting clocks. As individuals, we can do our best — and as communities, we can push for thoughtful policy.

Conclusion

Time changes seem trivial, but they quietly take a toll on our sleep, mood, and health. With growing awareness, we can choose better paths — both as individuals and as communities. By preparing ourselves and pushing for sensible policies, we can stay in sync with nature and protect our well-being.

Sources

  1. News Medical Life Sciences “Experts urge U.K. to end daylight saving time, citing negative impacts on sleep and circadian health”

  2. BMC “Lingering impacts on sleep following the Daylight Savings Time transition in the Project Baseline Health Study”

  3. CarInsurance.org “10 Worst States for Daylight Saving Time Fatal Crashes (New Study)”

  4. United States Studies Centre “Daylight savers or night wasters? The case against permanent daylight saving time in the United States”

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