Daylight Saving Time Impacts Sleep and Heart Health, Says Global Scientific Review
A new large-scale review of global scientific studies has revealed how the biannual switch to and from Daylight Saving Time (DST) impacts health, sleep, and safety. The research confirms that these time changes are associated with increased heart attack risks, deadly traffic accidents, changes in crime rates, and mixed effects on sleep. The findings reignite the debate about whether shifting clocks is beneficial or harmful to public health.
Study Overview: A Comprehensive Global Review
An international team of scientists from universities and research institutes worldwide conducted the systematic review. The authors include experts in chronobiology, cardiology, psychology, neuroscience, and sleep research: Aiste Steponenaite, Jonas P. Wallraff, Ursula Wild, Lorna Brown, Ben Bullock, Gurprit S. Lall, Sally Ferguson, Russell G. Foster, Jennifer Walsh, Greg Murray, Thomas S. Erren, and Philip Lewis.
These researchers represent institutions such as the University of Oxford (UK), University of Surrey (UK), Monash University (Australia), University of Adelaide (Australia), University of Manchester (UK), and several others. Their combined expertise covers sleep medicine, biological rhythms, epidemiology, and public health.
The results were published on the preprint platform medRxiv in March 2025 under the title “Daylight-Saving Time & Health: A Systematic Review of Beneficial & Adverse Effects” (DOI:10.1101/2025.03.17.25324086).
The authors emphasize that the study has not yet undergone peer review, so the conclusions should be considered preliminary.
How the Study Was Conducted
The researchers carried out an extensive review of the scientific literature, systematically searching five major databasesβMedline, Web of Science Core Collection, Scopus, PsychINFO, and EconLitβcovering studies published up to September 1, 2024. Their goal was to gather global evidence on the health impacts of both the start and end of Daylight Saving Time, as well as the effects of living under DST or standard time.
They screened thousands of records and selected 149 relevant studies from 36 countries, ensuring a wide geographical representation and diverse population groups. The selected studies included a variety of research designs, such as large national registry analyses, observational studies, and smaller controlled trials.
The review covered multiple health outcomes, including:
- Cardiovascular events like heart attacks and strokes
- Traffic and workplace accidents
- Sleep duration and circadian rhythm disruptions
- Psychiatric and neurological outcomes
- General mortality rates.
For each study, the team assessed methodological quality using the Joanna Briggs Institute checklist for quasi-experimental studies. Special attention was paid to the strength of evidence, consistency of results, and potential biases.
The researchers also differentiated between the impacts of the spring transition (DST-Onset) and the autumn transition (DST-Offset). In addition, they analyzed how long-term exposure to DST or standard time influences health, rather than focusing solely on short-term effects immediately after the clock changes.
This rigorous and structured approach allowed the authors to present the most comprehensive synthesis of existing evidence on the health impacts of Daylight Saving Time transitions.cks or traffic accidents. This review stands out by covering diverse health outcomes and global data.
What Makes This Study Different
This is the largest and most comprehensive review to date on the health impacts of DST. Unlike earlier research, this study:
- Assesses multiple health domains in one framework
- Differentiates between the effects of switching clocks forward (DST-Onset) and backward (DST-Offset)
- Analyzes not just the transition days but also the impact of living with permanent summer or winter time.
Key Findings: What the Research Reveals
1. Increased Risk of Heart Attacks After Clocks Go Forward
The review found that the week after moving clocks forward in spring leads to a measurable rise in heart attacks. People with pre-existing heart conditions are especially vulnerable. The sudden shift reduces sleep duration and stresses the cardiovascular system.
Example: A person with a heart condition forced to wake up earlier for work may face a higher risk of a heart attack during this week.
2. Deadly Road Accidents Spike After the Spring Shift
Fatal road accidents increase after the spring DST onset. Sleep loss and misalignment between body clocks and social schedules are likely factors.
Example: Drivers commuting in darker mornings after the time change may experience reduced attention, causing more accidents.
3. Crime Patterns Shift with DST
Interestingly, the start of DST leads to a short-term drop in violent crimes like assaults, possibly because there is more evening daylight when people are active outdoors. Conversely, crime involving physical harm rises when DST ends.
Example: Longer daylight hours in the evening reduce opportunities for street crimes.
4. Mixed Effects on Sleep Duration
The spring shift reduces sleep only for people with early school or work schedules. For others, changes are minimal. However, when clocks move back in autumn, people tend to sleep longer.
Example: Teenagers with early classes suffer more sleep loss, while adults with flexible schedules may not notice a change.
5. Mortality Rates Drop Slightly After Returning to Standard Time
Surprisingly, returning to standard time in fall is linked to a small decrease in overall deaths and workplace accidents, likely due to longer sleep duration.
Example: Fewer fatal workplace incidents happen in the weeks after the fall transition.
Impact on Cognitive Abilities: How Clock Changes Could Affect the Brain
The review also considered potential links between Daylight Saving Time transitions and cognitive functions. While direct evidence of measurable cognitive decline was limited, scientists pointed to indirect pathways that could impair brain performance.
Sleep loss and disruption of circadian rhythms caused by DST can negatively affect attention span, memory, reaction speed, and decision-making. This is especially critical in the days immediately following the spring clock change, when sleep deprivation is most pronounced.
These impairments may not only reduce daily productivity but also increase the risk of accidents in high-stakes professions, such as driving, aviation, healthcare, and emergency services. Students and shift workers are among the most vulnerable groups, as their schedules often conflict with natural sleep cycles.
Although further research is needed to measure long-term cognitive impacts, the study highlights how even minor disruptions to sleep and biological rhythms can have broader consequences for mental performance, concentration, and safety.
Why It Matters: What This Means for Public Health, Work, and Education
The findings of this global review carry important lessons for healthcare systems, educators and society as a whole. Even a one-hour clock change can have ripple effects far beyond losing a bit of sleep.
For the medical community, the evidence strengthens calls to treat clock changes as a cardiovascular risk factor, especially for people with existing heart conditions. Hospitals and clinics could plan preventive measures around these periods.
In workplaces, the increased risk of accidents following the spring transition raises the need for companies to review safety protocols and shift schedules, particularly in industries involving heavy machinery or transportation.
Schools could also consider the impact of early start times during the spring transition, as students may be more vulnerable to sleep loss, which could affect learning and concentration.
More broadly, the study highlights the need to better understand the health impacts of seasonal clock changes and to explore ways to reduce potential risks for vulnerable groups.
Ultimately, this research reframes the clock change not as a minor inconvenience, but as a public health issue worth serious attention.
Tips for Coping with the Spring Clock Change
Experts recommend several strategies to minimize health risks during the transition to Daylight Saving Time:
- Gradually shift your bedtime earlier by 15β20 minutes a few days before the change.
- Prioritize good sleep hygiene, including limiting screen time before bed and avoiding caffeine in the afternoon.
- Get exposure to natural morning light to help reset your body clock.
- Avoid intense physical or mental stress in the first days after the switch.
- Practice mindfulness or relaxation techniques to reduce stress and improve sleep quality.
- Allow extra time for commutes to reduce accident risks.
Conclusion: Assessing the Pros and Cons of Clock Changes
The review provides the most extensive evidence so far that DST has both positive and negative effects on health, safety, and society. The spring transition carries clear risks of heart attacks and accidents, while longer daylight may reduce violent crime. Returning to standard time improves sleep and reduces mortality. Rather than eliminating DST outright, the study recommends targeted measures to mitigate risks while preserving the potential benefits of daylight.
These findings shed new light on how even a simple clock change can ripple through daily life, subtly influencing well-being, productivity, and safety. Scientists stress the need for greater awareness of these effects, especially during the spring shift when health risks peak.
