Permanent Standard Time Vs. Daylight Saving: Health Benefits

Twice a year, Americans move their clocks forward or back. Some see it as a minor inconvenience. But new science says this clock-shifting has serious consequences for our health.

A major study published in Proceedings of the National Academy of Sciences (PNAS) modeled what would happen if the United States adopted permanent Standard Time (ST), permanent Daylight Saving Time (DST), or kept the current biannual switching system.

The results are striking: permanent Standard Time could prevent millions of cases of obesity and hundreds of thousands of strokes. Permanent DST also offered some benefits, but smaller ones. The current system—shifting clocks twice a year—was the worst for health.

This research forces us to ask: Who really benefits from DST, and at what cost? While some businesses gain revenue from longer evenings, the population pays with disrupted body clocks, poorer sleep, and higher disease risk.

The debate is no longer just about whether you like “lighter evenings” or “brighter mornings.” It is about whether we value short-term economic activity or long-term public health and healthcare savings.

The Study: Modeling Health Under Different Time Policies

The new study, published in Proceedings of the National Academy of Sciences (PNAS) in 2025, asked a simple but essential question: What happens to our health if the U.S. stops switching clocks?

How the study worked

Researchers created a model of the circadian burden—the strain our internal body clock experiences when social time doesn’t match natural sunlight.
They ran the model under three scenarios:
1. Current policy: Switching twice a year between Standard Time and Daylight Saving Time.
2. Permanent Daylight Saving Time (DST).
3. Permanent Standard Time (ST).
They then linked this circadian burden to real public health data on obesity and stroke from U.S. counties.

What they found

Permanent Standard Time (ST) would have the biggest health payoff:
- ~2.6 million fewer cases of obesity.
- ~300,000 fewer strokes.
Permanent Daylight Saving Time (DST) would help, but less:
- ~1.7 million fewer obesity cases.
- ~220,000 fewer strokes.
Current policy of switching clocks was the worst—causing the greatest circadian misalignment and highest health risks.

Keeping a permanent standard time prevents millions of obesity and strokes — Permanent Standard Time aligns with your body clock—preventing millions of obesity cases and strokes, while DST and clock switching fall short

Why it matters

These numbers aren’t small. Obesity and stroke drive up healthcare costs, shorten lives, and reduce quality of life. The study suggests that a simple policy change—choosing the right clock—could save lives and billions of dollars in medical spending.

The Circadian Rhythm and Why Its Disruption Is Unhealthy

Our bodies run on an internal clock called the circadian rhythm. This rhythm follows a 24-hour cycle, tightly linked to the rising and setting of the sun. When our daily schedules line up with natural light, our bodies function smoothly. When they don’t, stress builds up inside us.

How the body clock works

Morning light: Sunlight in the morning signals the brain to stop making melatonin, the sleep hormone. Cortisol and other “wake-up” signals rise, boosting alertness and energy.
Daytime: Hormones, body temperature, and metabolism follow predictable cycles, supporting digestion, activity, and focus.
Evening darkness: As the sun sets, melatonin rises again, helping us feel sleepy and ready for deep rest.

Daylight savings time disrupts the circadian rhythm — The Body Clock Affects the Daily Body Processes

What happens when the rhythm is disrupted

When social time is out of sync with solar time—as happens with late sunsets under DST—the circadian rhythm is thrown off. This mismatch has wide-reaching effects:

Poor sleep quality and insomnia.
Weight gain and obesity from disrupted hunger hormones and insulin resistance.
Higher blood pressure and risk of heart disease.
Increased risk of stroke, especially right after clock changes.
Mood problems like depression, fatigue, and brain fog.

Why clock policies matter

Time policies are not just about convenience. They decide whether the sun is high in the sky when we wake up—or whether we drag ourselves through mornings in darkness. Permanent Standard Time keeps our clocks closer to natural sunlight, giving the circadian rhythm the alignment it needs to protect health.

Who Benefits From Daylight Saving Time (DST)?

If the science is clear that Daylight Saving Time disrupts our circadian rhythm, why do so many groups still support it? The answer is simple: money.

DST shifts an hour of daylight into the evening, and certain industries profit from that extra sunlight.

The main winners under DST

Retail stores – Shoppers are more likely to stop and buy after work when it’s still light outside.
Golf courses – Golf has been one of the strongest lobbyists for DST. A U.S. Congressional report once estimated that golf gained about $400 million a year from longer evening play.
Restaurants and tourism – Outdoor dining, amusement parks, and tourist attractions see more visitors when evenings are bright.
Sports and recreation businesses – Tennis courts, swimming pools, and stadiums all benefit from extra daylight.

What about energy savings?

DST was once promoted as a way to save electricity. However, modern studies indicate that the effect is minor or even negative. While people may use less lighting, they often use more air conditioning in the evening and more driving fuel, wiping out most of the savings.

Bottom line

DST mainly benefits business sectors tied to consumer spending and leisure. The health costs—obesity, strokes, lost sleep—are paid by the population at large, while the profits flow to a few industries.

Who Benefits From Permanent Standard Time (ST)?

Unlike DST, which mainly benefits businesses, Permanent Standard Time (ST) benefits almost everyone by aligning social time with natural sunlight. The new PNAS study shows it would prevent millions of obesity cases and hundreds of thousands of strokes. However, the health benefits extend far beyond just disease statistics.

Children and teenagers

Mornings are brighter, making it easier to wake up.
Better alertness improves school performance and reduces early-morning accidents on the way to school.

Workers

Exposure to morning light leads to a better mood and increased productivity throughout the day.
Reduced fatigue lowers the risk of workplace accidents and errors.

Older adults

Lower risk of stroke and heart problems, which rise sharply when circadian rhythms are disrupted.
Better sleep quality supports mental health and immune function.

Healthcare system

With ~2.6 million fewer obesity cases and ~300,000 fewer strokes, hospitals and clinics face less strain.
Lower disease burden means billions of dollars saved in treatment costs each year.

Society as a whole

A healthier population lives longer, stays more active, and contributes more to communities and the economy.
Benefits are broadly shared, not concentrated in just a few industries.

Bottom line: Permanent Standard Time is the option that promotes health, safety, and long-term sustainability.

Health Care Cost Savings From Permanent Standard Time (ST)

The health gains predicted by the PNAS study are impressive on their own. But what do they mean in dollars? Preventing millions of obesity cases and hundreds of thousands of strokes would also save the U.S. billions in healthcare costs every year.

Obesity costs

Obesity already costs the U.S. about $173 billion per year in extra medical spending.
The study predicts ~2.6 million fewer obesity cases under Permanent Standard Time.
Even a conservative estimate—just $1,000 saved per prevented case—would equal $2.6 billion in annual savings. At higher cost-per-case estimates, the savings could be much greater.
💡 It could be much more than $2.6 billion, since obesity is strongly linked to cardiovascular disease, cancer, diabetes, and many other conditions that also drive up healthcare costs.

Stroke costs

Stroke care costs the U.S. around $56 billion annually in healthcare services, lost productivity, and long-term disability.
Permanent Standard Time could prevent ~300,000 strokes.
With the average cost of stroke care often exceeding $40,000 in the first year alone, this translates to billions in avoided costs, much of it covered by Medicare and Medicaid.

Billions in health care dollars will be saved by going into permanent savings time and stopping DST

The Medicare connection

Medicare is the single largest payer for stroke hospitalizations, since strokes occur most often in older adults.
By lowering stroke risk, Permanent Standard Time would directly ease pressure on Medicare’s already stretched budget.
This means not only healthier people, but also stronger federal finances.

Total impact

When combined, the reduced costs of treating obesity, stroke, and related complications could reach tens of billions of dollars every year. These savings significantly outweigh the relatively small economic boost DST provides to the retail and leisure industries.

The Contrast: Economics vs. Health

The debate over clock policy boils down to this: Who wins, and at what cost?

Daylight Saving Time (DST)

Benefits a narrow set of industries—retail, golf, tourism, and restaurants—by giving people more light in the evening to shop or play.
Studies suggest the GDP bump is tiny, likely a fraction of one-tenth of a percent, or a few billion dollars at most.
The costs include more circadian disruption, a higher risk of heart attacks, obesity, strokes, and billions in added healthcare spending.

Permanent Standard Time (ST)

Aligns our daily schedule with the body’s natural circadian rhythm.
Brings health gains to nearly everyone: children, workers, older adults, and patients.
Prevents millions of obesity cases and hundreds of thousands of strokes.
Saves the healthcare system tens of billions of dollars annually, especially in Medicare and Medicaid spending.

The choice in plain terms

DST = a modest boost to evening leisure businesses, short-term consumer spending.
Standard Time = a healthier population, lower healthcare costs, and stronger long-term productivity.

Standard Time wins over DST in health, economics, and productivity.

This makes the policy question clear: Do we prioritize narrow economic interests, or do we choose lasting health benefits for all Americans?

Conclusion

The debate over time policy is not just about whether we prefer light evenings or brighter mornings. It is a question of health versus commerce.

The latest PNAS study shows that permanent Standard Time would prevent millions of obesity cases and hundreds of thousands of strokes. These health improvements would translate into tens of billions in healthcare savings, easing the financial burden on families, hospitals, and Medicare.

By contrast, Daylight Saving Time primarily benefits a few industries—retail, restaurants, golf, and tourism.

The economic boost to GDP is small, measured in billions, while the health costs are vast, measured in lives lost and medical bills that taxpayers ultimately cover.

In short:

DST offers narrow economic gains but broad health risks.
Permanent Standard Time delivers broad health benefits and long-term savings for everyone.

As policymakers consider ending the biannual clock change, the evidence makes the healthier choice clear. Aligning our clocks with the sun through Permanent Standard Time is not only better for our bodies—it is also smarter for our economy and society as a whole.

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References:

Weed, Lara, and Jamie M. Zeitzer. “Circadian-Informed Modeling Predicts Regional Variation in Obesity and Stroke Outcomes under Different Permanent US Time Policies.” Proceedings of the National Academy of Sciences of the United States of America, vol. 122, no. 38, 2025, e2508293122.
Farrell, Diana, Vijay Narasiman, and Marvin Ward Jr. Shedding Light on Daylight Saving Time. JPMorgan Chase Institute, 2016.
Kotchen, Matthew J., and Laura E. Grant. “Does Daylight Saving Time Save Energy? Evidence from a Natural Experiment in Indiana.” Review of Economics and Statistics, vol. 93, no. 4, 2011, pp. 1172–1185.
Smith, Austin C. “Spring Forward at Your Own Risk: Daylight Saving Time and Fatal Vehicle Crashes.” American Economic Journal: Applied Economics, vol. 8, no. 2, 2016, pp. 65–91.
Coren, Stanley. “Daylight Savings Time and Traffic Accidents.” New England Journal of Medicine, vol. 334, no. 14, 1996, pp. 924–925.
Centers for Disease Control and Prevention. “Adult Obesity Facts.” CDC, 2024.
Benjamin, Emelia J., et al. “Heart Disease and Stroke Statistics—2024 Update: A Report from the American Heart Association.” Circulation, vol. 149, no. 8, 2024, pp. e58–e252.
Howard, George, and Virginia J. Howard. “Twenty Years of Progress toward Understanding the Stroke Belt.” Stroke, vol. 51, no. 3, 2020, pp. 742–750.
Chmura Economics & Analytics. “The Economic Cost of Daylight Saving Time.” Chmura Blog, 2019.

Image credits:

Overview of biological circadian clock in humans-By NoNameGYassineMrabetTalk CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=3017148

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Permanent Standard Time vs. Daylight Saving Time

Introduction