A recent position statement in the Journal of Sleep Research presents evidence-backed findings on the impact of clock changes on sleep and circadian health. Experts conclude that shifting clocks, especially the one-hour advance in spring, harms health. They advocate for the end of Daylight Saving Time (DST) and recommend a return to Standard Time year-round.
History of Daylight Saving Time
Daylight Saving Time, also known as British Summer Time, shifts clocks forward by one hour in late March and back in October. Before DST, the UK followed Standard Time, or Greenwich Mean Time (GMT), all year, aligning more closely with natural daylight cycles.
DST was first introduced during World War I and reinstated in World War II. The current practice of twice-yearly clock changes began in 1972. In 2018, the European Parliament discussed ending DST, but the UK has not moved forward with this. However, there is an ongoing debate about making either DST or Standard Time permanent.
Because the British Standard Time is based on the Prime Meridian, the UK—located west of this line—experiences later sunrises and sunsets. Seasonal changes in daylight particularly impact northern areas, resulting in notably late winter sunrises and reduced morning sunlight before work and school.
Impact of Light on Circadian Rhythms
Human circadian rhythms, or 24-hour internal clocks, regulate essential functions like sleep and metabolism, heavily influenced by light exposure. Morning light is especially crucial as it supports a natural wake-sleep cycle. Conversely, exposure to evening light delays sleep onset, posing challenges for those with early routines, including teenagers.
While both sunlight and artificial light affect body clocks, sunlight is more effective. DST, however, does not increase sunlight but rather shifts routines to favor evening light. In winter, a permanent DST setup could worsen sleep and circadian misalignment due to reduced morning light.
International sleep experts caution against permanent DST, citing potential harm to sleep and health. The geographical position of the UK, with delayed winter sunrises under DST, makes this recommendation even more relevant.
Why Standard Time Is Recommended
Clock changes in March and October disrupt sleep and circadian rhythms, with the spring shift leading to sleep loss and immediate health risks like reduced productivity and increased safety concerns. Long-term effects of DST are less clear but may negatively affect sleep and health, especially in spring and autumn.
Permanent DST would result in later winter sunrises, reducing morning light and affecting northern and western UK areas the most. Additionally, permanent DST would place the UK in alignment with regions farther east, like Western Poland, creating a disconnect from local solar time and potentially affecting sleep and health.
Research shows that living out of sync with solar time disrupts sleep and health. While DST may provide extra evening light in spring and autumn, it sacrifices essential morning light, particularly in winter. By contrast, permanent GMT would align more closely with the UK’s natural daylight, supporting healthier sleep patterns. Summer sunsets under GMT would still allow for evening activities, while autumn and winter would see more beneficial morning sunlight.
Any decision to adjust time zones in the UK would also require coordination with Ireland to maintain consistent time across the Irish border.
Conclusion
The British Sleep Society and other organizations recommend adopting permanent GMT for improved sleep and health. They support abolishing the biannual clock changes and strongly oppose permanent DST due to its potential health risks. Returning to year-round GMT would mitigate circadian rhythm disturbances, benefitting overall sleep and well-being.
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