Physicists refute famous 2025 study claiming daylight saving time poses severe health risks

University of Seville

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In 2025, Lara Weed and Jamie M. Zeitzer of Stanford University published an article linking the practice of seasonal time changes (Daylight Saving Time) to negative health outcomes, ranging from acute symptoms (heart attacks and strokes) to chronic conditions (obesity). Now, Professors José María Martín-Olalla (University of Seville) and Jorge Mira Pérez (University of Santiago de Compostela), after analyzing the methodology applied in that study, have concluded that "what the world read as scientific evidence against the time change has turned out to be a mathematical illusion."
The same journal that disseminated the controversial article, PNAS (Proceedings of the National Academy of Sciences), has just published a letter signed by Martín-Olalla and Mira Pérez, demonstrating that the study’s conclusions are not supported by actual evidence.
The original article by Weed and Zeitzer gained significant global traction in the fall of 2025 due to its striking conclusions and its use of the PLACES database (Population Level Analysis and Community Estimates). This database, managed by the U.S. Centers for Disease Control and Prevention (CDC), contains information on the prevalence of 29 syndromes and diseases at the local level. The PLACES data were contrasted against a circadian model developed by the authors.

A Critical Error

The work of Professors Martín-Olalla and Mira Pérez reports a grave error in the study's methodological foundations. The original model computes the difference between the rhythm of the biological clock—the circadian rhythm, determined by the time at which body temperature is at its minimum—and the rhythm of the Earth's rotation. According to the original authors, this difference represents the "regulatory circadian shifting necessary to stay synchronized with the outer world."
Global health effects were inferred from the annual sum of these daily readjustments. However, when performing this calculation, the authors consistently accumulated the magnitude of the readjustment, regardless of whether it was positive or negative. "The use of absolute readjustments instead of real readjustments is the critical error," note Martín-Olalla and Mira. They show that this methodology merely captures the "noise" of the model and, therefore, cannot predict net health effects.
Professor Mira explains: "What the authors did makes little sense; it is as if, while driving, we recorded every small adjustment made by moving the steering wheel back and forth to stay in the lane, but then added them all up in the same direction to report a large value instead of allowing them to compensate for each other. By their logic, maintaining a straight course with small left-and-right adjustments (what actually happens) would be the same as a car drifting further and further in one direction until it ends up facing the wrong way. This alone refutes the study's conclusions."
Professor Martín Olalla adds: "We analyzed the 'guts' of the model and saw that the daily readjustment was small—similar to the model's temporal precision—and fluctuating: one direction one day, the opposite the next, with no global trend leading to significant desynchronization, which is exactly how a readjustment should function. Consequently, the annual cumulative total of these readjustments was zero, even with the time change. The metric used appears to have been chosen with the intent of ensuring the current time-change policy yields the worst possible results; the readjustments triggered by the spring and autumn shifts are made to contribute in the same direction instead of compensating for each other. In this sense, the study’s findings resemble a self-fulfilling prophecy. The fact is that the 'absolute cumulative readjustment' they report is approximately 20 hours per year, which is nothing more than an average of about 3 minutes per day, sometimes in one direction and sometimes in the other. Given the information provided in the study, it is difficult to understand how such a weak value (a mere 0.3%) can be epidemiologically linked to the prevalence of disease."
Concluding their letter, Professors Martín Olalla and Mira pose a fundamental question: What prior expectations did the original authors have when they decided to associate global sociosanitary outcomes with the noise of their own model? "We see no prior hypothesis or causal link that justifies the analysis performed in the original study. This invalidates the methodology and, consequently, the reported findings: the authors cannot conclude that eliminating the time change would lead to a decrease in the prevalence of obesity or acute medical events," they affirm.

 

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Journal

Proceedings of the National Academy of Sciences

DOI

10.1073/pnas.2532075123 

Article Title

The sum of absolute circadian shifts: Questioning the metric linking daylight saving time policy to stroke and obesity

Article Publication Date

17-Apr-2026

 

Scientists unveil how heat-loving enzyme could help improve plastic recycling

Researchers reveal cutinase combines a rigid core with a flexible active site, providing insights into heat resistance and plastic degradation

Tokyo University of Science

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The cutinase enzyme combines a rigid α/β-hydrolase core with a flexible lid loop near the active site. Structural comparison suggests that the lid loop undergoes conformational changes more readily than the rigid core.

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Credit: Professor Tatsuya Nishino from Tokyo University of Science, Japan

Among the various plastic recycling methods being explored, one promising approach is biological plastic recycling, also known as biorecycling, which utilizes enzymes or microorganisms to break down polymer molecules. One group of enzymes attracting attention is microbial cutinases. These enzymes are naturally produced by bacteria and fungi to degrade the waxy outer layer of plants, known as the cuticle. Because they can act on similar chemical bonds, they are considered promising for recycling poly(ethylene terephthalate) (PET), a plastic used in bottles and synthetic fibers.

However, applying these enzymes in industrial settings is not straightforward. PET is most efficiently degraded at temperatures around 70 °C, where it becomes more flexible and easier to process. At such high temperatures, enzymes must maintain a stable overall structure to avoid unfolding, while also retaining flexibility at their active site for molecular recognition and catalysis. This creates a design challenge, as structural rigidity and flexibility are often opposing properties.

To better understand this balance, a team of researchers led by Professor Tatsuya Nishino from the Department of Biological Science and Technology, Tokyo University of Science (TUS), Japan, along with Assistant Professor Sho Ito from the same department, and graduate researchers Mr. Ryohei Nojima (M.Sc., 2022) and Ms. Lirong Chen (M.Sc., 2024) from TUS, examined a heat-tolerant cutinase enzyme from the fungus Chaetomium thermophilum. The enzyme, known as CtCut, was analyzed under conditions relevant to high-temperature PET recycling to better understand how it maintains structural stability and catalytic potential. The study was published in Volume 16, Special Issue 4 of the journal Crystals on March 24, 2026.

“Plastic waste has become a severe problem in recent years, necessitating environmentally friendly recycling technologies. Thus, our aim was to contribute to the development of practical recycling technologies by clarifying the molecular basis of enzymes that function even under high-temperature conditions,” says Prof. Nishino.

For the study, the team created several versions of the enzyme. This included the wild-type (CtCutWT), which is the unmodified form, and a mutant version, CtCutS136A, in which the amino acid serine at position 136 is replaced with alanine.

They then determined the enzyme’s structure and assessed its thermal stability using differential scanning calorimetry, heating the protein from 30 °C to 100 °C to analyze how it absorbed heat.

Structurally, the enzyme adopts a highly stable α/β-hydrolase fold, a common architecture among cutinases. Covering the active site is a flexible lid loop that can open and close. In its closed state, the active site is less accessible, but upon binding a molecule, the lid changes shape to allow binding and catalysis.

Notably, a chloride ion was found near the active site even when no substrate was present, suggesting that the active site forms a positively charged electrostatic microenvironment that may facilitate ligand binding.

As the enzyme was heated, it showed a two-step unfolding process, with a gradual transition beginning at around 60 °C, followed by a second transition near 65–70 °C. This indicates that different parts of the enzyme lose stability at different temperatures, suggesting the presence of structurally distinct regions within the protein.

“Our findings suggest the possibility of functional division within the enzyme. We observed that the mobile region near the active site undergoes structural changes in response to ligand binding, and that thermal denaturation proceeds in multiple stages,” says Prof. Nishino.

These findings support the idea that enzymes designed for plastic degradation may require both a stable overall structure and a flexible active site. The rigid core provides the thermal stability needed to withstand industrial conditions, while the flexible lid loop may help the enzyme adapt to bound molecules.

By better understanding this balance between stability and flexibility, the study provides new insights into the function of heat-tolerant enzymes and how they can be improved.

“Our study may lead to the development of technologies for efficiently decomposing and recycling PET in the future by providing design guidelines for enzymes that possess both heat resistance and potential catalytic capabilities for polymer degradation. This may address the growing challenge of plastic waste and help realize a sustainable resource-recycling society,” concludes Prof. Nishino.

 

***

 

Reference       
DOI: 10.3390/cryst16040217

 

About The Tokyo University of Science
Tokyo University of Science (TUS) is a well-known and respected university, and the largest science-specialized private research university in Japan, with four campuses in central Tokyo and its suburbs and in Hokkaido. Established in 1881, the university has continually contributed to Japan's development in science through inculcating the love for science in researchers, technicians, and educators.

With a mission of “Creating science and technology for the harmonious development of nature, human beings, and society," TUS has undertaken a wide range of research from basic to applied science. TUS has embraced a multidisciplinary approach to research and undertaken intensive study in some of today's most vital fields. TUS is a meritocracy where the best in science is recognized and nurtured. It is the only private university in Japan that has produced a Nobel Prize winner and the only private university in Asia to produce Nobel Prize winners within the natural sciences field.

Website: https://www.tus.ac.jp/en/mediarelations/

 

About Professor Tatsuya Nishino from Tokyo University of Science
Dr. Tatsuya Nishino is a Professor at the Department of Biological Science and Technology, Tokyo University of Science, Japan. He earned his Doctor of Medicine degree from Osaka University in 2001. His research focuses on structural biology, particularly protein structure analysis using X-ray crystallography. His work includes the structural analysis of protein complexes to better understand molecular function. He has authored over 25 refereed papers with over 2,000 citations, contributing extensively to the field of molecular and structural biology.

Funding information
This work was partly supported by the Japan Society for the Promotion of Science (JSPS) KAKENHI under Grant Numbers 20K06512 and 23K05671.

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Journal

Crystals

DOI

10.3390/cryst16040217 

Method of Research

Experimental study

Subject of Research

Not applicable

Article Title

Crystal Structures of a Thermophilic Cutinase from Chaetomium thermophilum Reveal Conformational Dynamics of the Catalytic Lid Loop

 

Millimeter-scale resolution in fiber-optic sensing: single-ended technique advances infrastructure monitoring

Researchers demonstrate that overcoming signal distortions enables record-breaking spatial resolution in single-access distributed fiber-optic sensing

Shibaura Institute of Technology

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Researchers demonstrate that operating at modulation frequencies close to Brillouin bandwidth and suppressing signal distortions allows BOCDR to achieve a world-record spatial resolution of 6 mm.

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Credit: Prof. Yosuke Mizuno from Yokohama National University, Japan https://ieeexplore.ieee.org/document/11278604

Distributed fiber-optic sensors are widely used to monitor temperature and strain in infrastructure, but their spatial resolution has long been limited. In a new study, researchers from Shibaura Institute of Technology and Yokohama National University, Japan, have demonstrated that operating near a previously avoided frequency regime and suppressing signal distortions allows reflection-based sensing to achieve a world-record spatial resolution of 6 mm among single-end-access configurations. This enables precise monitoring of temperature and strain in infrastructure.

Distributed fiber-optic sensing technologies play a crucial role in monitoring temperature and strain across large structures such as bridges, tunnels, pipelines, and buildings. Unlike conventional point sensors, distributed fiber-optic sensors provide continuous measurements along their entire length, allowing early detection of damage or abnormal conditions. However, one persistent challenge has been spatial resolution—the ability to pinpoint exactly where a change occurs. Improving resolution without complicating system design has remained a central goal in fiber-optic sensing research.

One promising technique, known as Brillouin optical correlation-domain reflectometry (BOCDR), enables distributed sensing using light injected from only one end of the fiber. This reflection-based configuration simplifies installation and allows measurements even if the fiber is damaged. BOCDR also offers higher spatial resolution than many other Brillouin-based methods. Yet, its performance has been constrained by a widely accepted assumption: operating near or beyond the Brillouin bandwidth, a frequency range intrinsic to the fiber, was believed to cause unstable signals and unreliable measurements. As a result, this operating regime has largely been avoided, limiting achievable resolution.

In a new study, a team of researchers led by Prof. Heeyoung Lee from Shibaura Institute of Technology, Japan, along with Prof. Yosuke Mizuno from Yokohama National University, Japan, and Mr. Keita Kikuchi from Shibaura Institute of Technology, Japan, experimentally investigated BOCDR operation at modulation frequencies close to the Brillouin bandwidth. Their findings were published in the Journal of Lightwave Technology on April 1, 2026.

“To verify whether the Brillouin bandwidth limitation was truly fundamental or simply not well understood, we examined the origin of the signal distortions and explored ways to control them. Notably, we discovered that this forbidden operating region can be used to significantly enhance spatial resolution,” says Prof. Lee.

The researchers observed that at higher modulation frequencies, periodic distortions appeared in the Brillouin gain spectrum, interfering with the accurate extraction of temperature and strain information. These distortions degrade the linear relationship between temperature/strain and the Brillouin frequency shift, particularly at high spatial resolution.

Rather than treating these distortions as unavoidable, the team carefully analyzed their physical origin and developed a signal-processing method to suppress them. By mapping the measured spectra into the frequency domain and selectively removing the modulation-induced components, they restored the stability and linearity of the Brillouin signal. This approach allowed BOCDR to operate reliably in a frequency regime that had previously been considered impractical.

Using this strategy, the researchers achieved distributed temperature and strain measurements with a spatial resolution of 6 mm—the highest ever reported for single-ended Brillouin sensing. In experimental demonstrations, the system successfully detected temperature changes confined to millimeter-scale fiber sections and resolved abrupt strain-like transitions introduced by short fiber segments with different optical properties.

The implications of this work extend beyond laboratory demonstrations. Aging infrastructure and increasing exposure to natural disasters demand sensing technologies capable of detecting subtle, highly localized changes before they escalate into serious damage to public safety and maintenance efficiency. Achieving millimeter-scale resolution using a simple, single-end-access fiber configuration makes practical deployment of fiber-optic sensors more feasible across civil engineering, energy, transportation, and robotics-related industries.

“Our study addresses the limitations of conventional sensors that miss the detection of subtle changes and proposes an approach that can be used for monitoring the integrity of optical waveguides, sensing the shape of flexible structures, and future robotic systems,” says Prof. Lee.

By overcoming a long-standing performance barrier, this study opens new pathways for distributed sensing systems that function like a “nerve network,” continuously monitoring the health of critical structures.

 

About Shibaura Institute of Technology (SIT), Japan

Shibaura Institute of Technology (SIT) is a private university with campuses in Tokyo and Saitama. Since the establishment of its predecessor, Tokyo Higher School of Industry and Commerce, in 1927, it has maintained “learning through practice” as its philosophy in the education of engineers. SIT was the only private science and engineering university selected for the Top Global University Project sponsored by the Ministry of Education, Culture, Sports, Science and Technology and had received support from the ministry for 10 years starting from the 2014 academic year. Its motto, “Nurturing engineers who learn from society and contribute to society,” reflects its mission of fostering scientists and engineers who can contribute to the sustainable growth of the world by exposing their over 9,500 students to culturally diverse environments, where they learn to cope, collaborate, and relate with fellow students from around the world.

Website: https://www.shibaura-it.ac.jp/en/

About Professor Heeyoung Lee from SIT, Japan

Dr. Heeyoung Lee is a Professor at the Graduate School of Engineering and Science, Shibaura Institute of Technology, Japan. She received a Ph.D. in Electrical and Electronic Engineering from the Institute of Science Tokyo, Japan, in 2019. Her research interests include fiber-optic sensing, polymer optics, and optoelectronics. She has been honored with multiple awards, including the NF Foundation R&D Encouragement Award 2019, the Kashiko Kodate Promotion and Nurturing of Female Researchers Contribution Award 2021, and the SCAT President’s Award 2025.

Funding Information

This work was supported in part by JSPS KAKENHI under Grant 21H04555 and Grant 22K14272 and by research grants from the Telecommunications Advancement Foundation, and in part by Asahipen Hikari Foundation.

 

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Journal

Journal of Lightwave Technology

DOI

10.1109/JLT.2025.3640608 

Method of Research

Experimental study

Subject of Research

Not applicable

Article Title

BOCDR achieving 6-mm spatial resolution at modulation frequencies close to Brillouin bandwidth

Article Publication Date

19-Apr-2026

 

Emoji’s have feelings too, new study reveals

A new study has found that the brain reacts to emojis in a similar way that it reacts to seeing real human faces. 

👹👺👻👼👽👿💀😁😅💩

Bournemouth University

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A new study might make people re-think every WhatsApp or email they send. Researchers at Bournemouth University have found that the brain reacts to emojis in a similar way that it reacts to seeing real human faces. 

Facial expressions are a fundamental aspect of human social interaction. Whilst emojis are an extremely popular way for people to communicate, very little is known about the psychological response that they can generate.  

To address this question, participants in the study were connected to an EEG (electroencephalogram) machine to measure the electrical activity in their brains. One set of participants were shown human faces, the other shown emojis. All pictures portrayed different facial expressions including happiness, anger, and sadness. 

The researchers then compared the readings from the EEG machine across the two groups. 

Our findings showed that viewing emojis elicited neural response patterns similar to those involved in processing real human facial expressions,” said Madeline Molly Ely, a PhD student at Bournemouth University who led the study. “This suggests that emojis are not simply fun additions to digital communication but may be processed by the brain in ways comparable to genuine facial cues. In this sense, emojis can function as meaningful emotional signals during online interaction.” 

The reactions of the brain generally occurred quickly for both real and digital expressions, usually occurring within 145 to 160 milliseconds. The pattern of similarity was consistent with regions of the brain associated with face processing. 

The researchers’ takeaway message is that next time you drop a or in a message, remember that your brain, and everyone else’s will be taking them seriously.  

The study has been published in the journal Psychophysiology. 

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Journal

Psychophysiology

DOI

10.1111/psyp.70268 

Method of Research

Randomized controlled/clinical trial

Subject of Research

People

Article Title

Shared Neural Codes for Emotion Recognition in Emoji and Human Faces

 

Study suggests link between prenatal exposure to certain medications and increased autism risk

Research identifies commonly prescribed, sterol biosynthesis-inhibiting medications as potential contributors to neurodevelopmental vulnerability.

University of Nebraska Medical Center

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From left, corresponding author Karoly Mirnics, MD, PhD, and Eric Peeples, MD, PhD, lead author

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Credit: Kiley Cruse and Chuck Koster

OMAHA, Nebraska — A landmark study led by researchers at the University of Nebraska Medical Center (UNMC) and published in Molecular Psychiatry has identified a significant association between prenatal prescription of commonly utilized medications and the risk of autism spectrum disorder (ASD) in children. 

Analyzing 6.14 million maternal-child health records from the Epic Cosmos database —representing nearly one-third of all U.S. births between 2014 and 2023 — the team found that prescription of medications known to inhibit the cholesterol synthesis pathway were consistently associated with higher rates of ASD in offspring. 

While previous studies grouped medications by their indications, the UNMC team grouped prescribed medications together based on common effects and side effects on sterol biosynthesis. 

These sterol biosynthesis–inhibiting medications (SBIMs) include certain antidepressants, antipsychotics, anxiolytics, beta-blockers and statins. These are the generic names of the 14 medications studied: aripiprazole, atorvastatin, bupropion, buspirone, fluoxetine, haloperidol, metoprolol, nebivolol, pravastatin, propranolol, rosuvastatin, sertraline, simvastatin and trazodone. Many of these are among the most commonly prescribed medications in the United States, accounting for more than 400 million annual prescriptions. 

Key findings 

• Mothers prescribed at least one SBIM during pregnancy had a 1.47-fold higher risk of having a child diagnosed with ASD. Risk increased in a dose-dependent manner. For each additional SBIM co-prescribed, there was a 1.33 times increased risk of ASD, reaching 2.33-fold risk when four or more SBIMs were prescribed simultaneously. 

• Among the 196,447 children diagnosed with ASD in the cohort, 14.2% had prenatal SBIM exposure. 

• Use of SBIMs during pregnancy increased sharply over time, rising from 4.3% of pregnancies in 2014 to 16.8% in 2023. 

Why sterol biosynthesis matters 

Cholesterol is essential for fetal development, especially for the brain, the most cholesterol-rich organ. The fetal brain begins producing its own sterols around 19–20 weeks of gestation. Genetic disruptions in this pathway are known to cause severe developmental syndromes such as Smith-Lemli-Opitz syndrome (SLOS), in which up to 75% of children meet criteria for ASD. Many widely used medications can unintentionally interfere with this pathway. This study is the first nationwide investigation to evaluate the neurodevelopmental outcomes associated with prenatal exposure to this group of medications. 

A public health signal requiring attention 

“Our findings do not suggest that these medications are unsafe for adults,” said senior author Karoly Mirnics, MD, PhD, dean and director of the UNMC Munroe-Meyer Institute. “But they raise important questions about their use during pregnancy, a period when even small biochemical disruptions may have outsized effects on fetal brain development.” 

The authors stress that no pregnant patient should discontinue or alter medication without medical supervision, as many SBIMs are essential, often life-saving treatments. Instead, the study calls for a re-evaluation of prescribing practices and for developing safer alternatives for use during pregnancy. 

Potential next steps 

The research team proposes several actions to improve drug safety for pregnant patients: 

• Create a comprehensive list of medications with sterol-inhibiting effects. 
• Evaluate all new pharmaceuticals for unintended sterol pathway inhibition. 
• Increase provider education about medication-associated sterol disruption during pregnancy. 
• Discuss safer alternatives when discontinuing treatment is not possible. 
• Avoid prescribing multiple SBIMs for pregnant women whenever feasible. 
• Identify patients with genetic vulnerabilities in sterol metabolism, as they might be particularly sensitive to SBIM effects. 
• Invest in further research to understand mechanisms and mitigate risk. 

The work was conducted using the Epic Cosmos national data platform and included collaboration among UNMC’s Department of Pediatrics, Department of Biostatistics, Munroe-Meyer Institute, other UNMC departments and the Child Health Research Institute (CHRI). The study received support from UNMC/CHRI internal resources, the Dorothy B. Davis Foundation and the Nebraska Tobacco Settlement Fund. 

About UNMC  

As Nebraska’s only public academic health science center, the University of Nebraska Medical Center enrolls more than 4,800 students across six colleges, two institutes and a graduate studies program. A nationally recognized leader in research and innovation, UNMC’s mission is to create a healthier future for Nebraskans through premier education, research and clinical care, but its impact – rooted in a culture of collaboration, big ideas and public-private partnerships – goes far beyond, in areas that include infectious diseases, rural health, cancer research and treatments, global health security, intellectual and developmental disabilities, and simulation and experiential learning technologies. 

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Journal

Molecular Psychiatry

Method of Research

Data/statistical analysis

Subject of Research

People

Article Title

Study suggests link between prenatal exposure to certain medications and increased autism risk

Article Publication Date

16-Apr-2026