Canadian study warns permanent daylight saving could disrupt sleep and health
President Trump is pushing the United States Senate to adopt permanent daylight saving time, primarily to allow golfers to stay on course longer. However, a newly published Canadian research paper argues that the health costs of permanent DST could outweigh its benefits, recommending instead a shift to permanent standard time.
The Canadian Medical Association Journal study found that whilst permanent DST extends evening daylight for commuting and social activities, it prolongs darkness in winter mornings, disrupting circadian rhythms which normally run on a 24.2-hour cycle. Research cited in the analysis shows people on the western side of US time zones, where sun sets later, sleep approximately one hour less per week and experience lower productivity, with studies linking each additional hour of weekly sleep to around 5 percent higher long-term earnings. Education also suffers, with one Florida study finding that extra morning sunlight before school correlated with improved maths and reading scores comparable to meaningful class-size reductions.
- Permanent daylight saving time disrupts sleep and morning circadian rhythms
- Canadian researchers recommend permanent standard time instead
- Extended evening light reduces sleep and lowers productivity and earnings
New here? Start with this
Daylight saving time is the practice of setting clocks forward by one hour during certain periods of the year to extend evening daylight. Many countries have used this system for over a century, and most of the world currently switches between daylight saving time and standard time twice yearly. The current debate is about whether the United States should remain on daylight saving time permanently, rather than switching between the two.
A proposal to adopt permanent daylight saving time has gained recent attention after the US President pushed the Senate to support it. Supporters argue it provides benefits such as additional daylight in the evenings for activities and commuting. However, researchers have raised concerns about potential health effects, and a study from the Canadian Medical Association Journal has published findings questioning this approach.
The Canadian research indicates that permanent daylight saving time could disrupt the body's natural sleep cycle because humans operate on roughly 24.2-hour rhythms that naturally align with sunrise and sunset. When daylight saving time is permanent, winter mornings remain significantly darker for longer, which can disrupt these natural rhythms and lead to less sleep overall. Studies cited in the research suggest that people in areas where the sun sets later sleep less and experience reduced productivity, with wider implications for earnings, educational performance and long-term health outcomes.
Both sides, in good faith
The strongest fair case each way — we don't pick a winner.
The case for
Permanent daylight saving time preserves evening daylight for work, exercise and social activities that enhance quality of life and economic productivity. Whilst circadian rhythm adjustments merit consideration, the real-world costs may be overstated, and many people actively prefer and benefit from evening light for their lifestyle and wellbeing.
The case against
Permanent standard time respects the body's natural circadian rhythm aligned to sunrise and sunset patterns. The Canadian research demonstrates measurable harms including reduced sleep, lower productivity, and diminished educational outcomes, particularly for children who require morning light exposure for healthy development and academic performance.
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Originally published by The Register as “Permanent daylight saving time could be a public health time bomb”.