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

 

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.