Daylight Saving Time Effects on Health and Safety

Daylight Saving Time (DST) involves biannual advances and delays of the social clock by one hour, with the stated purpose of better aligning human activity with natural daylight. Although the energy savings remain contested, research increasingly emphasises the health and safety consequences of these transitions. Clock shifts induce circadian misalignment, sleep fragmentation and transient alterations in physiological processes, which have been linked to modest elevations in cardiovascular events, traffic accidents and markers of mental and immune dysfunction. Effects are most pronounced in the days immediately following the spring-forward transition, when reduced sleep duration and hormonal disruption may exacerbate sympathetic activity and impair cognitive vigilance. The global variation in latitude, timing of sunrise and regional work patterns further modulate these outcomes, informing policy discussions on the merits of permanent standard or summer time.

Research from Nature Portfolio

Recent analyses of large-scale time-use surveys across multiple countries have examined the long-term adaptation of sleep–wake and labour cycles to longstanding DST regulations. Data from over 10 000 respondents in regions spanning Europe and North America reveal that labour patterns remain remarkably stable across seasons when measured in local time, while sleep onset and offset continue to follow solar cues such as sunrise and sunset. These findings suggest that human activity cycles maintain an underlying synchrony with environmental light cues despite clock adjustments, shedding light on the complex interplay between social timing and biological rhythms over decades of DST practice.

Daylight Saving Time Effects on Health and Safety publication trend

The graph below shows the total number of articles in daylight saving time effects on health and safety across all publications each year (not limited to Nature Index journals).

Technical terms

Circadian rhythm: An intrinsic, roughly 24-hour cycle in physiological and behavioural processes driven by an internal biological clock.

Chronotype: An individual’s propensity for activity and alertness at particular times of day, often described as ‘morning’ or ‘evening’ preference.

Social jetlag: The mismatch between an individual’s biological time and the socially imposed timetable, typically quantified by differences in sleep timing between workdays and free days.

Acute myocardial infarction: A sudden blockage of blood flow to the heart muscle, commonly known as a heart attack, often precipitated by thrombotic events within coronary arteries.

References

1. Daylight Saving Time and Artificial Time Zones – A Battle Between Biological and Social Times. Frontiers in Physiology (2019).
2. Transition into daylight saving time influences the fragmentation of the rest-activity cycle. Journal of Circadian Rhythms (2006).
3. Daylight Saving Time and Acute Myocardial Infarction: A Meta-Analysis. Journal of Clinical Medicine (2019).
4. Daylight Saving Time Transitions and Road Traffic Accidents. Journal of Environmental and Public Health (2010).
5. Measurable health effects associated with the daylight saving time shift. PLOS Computational Biology (2020).
6. Daylight Saving Time Transitions: Impact on Total Mortality. International Journal of Environmental Research and Public Health (2020).
7. The long term impact of Daylight Saving Time regulations in daily life at several circles of latitude. Scientific Reports (2019).
8. Daylight Saving Time policy and energy consumption. Energy Reports (2021).