Dr Alanna Hare
President, British Sleep Society
Dr Simon Durrant
President, British Sleep Society
On the last Sunday of March, clocks in the UK will go forward. Sunrise and sunset will appear an hour later, marking the beginning of daylight saving time.
For centuries, time was defined locally, according to the position of the sun. This local mean time had one key advantage: it helped keep our circadian rhythms (body clocks) more closely aligned with the clock time.
Time zones impact on body
Railway timetables required consistent time across bigger distances and Greenwich Mean Time (GMT) was slowly adopted. A single national time zone results in later sunrises and sunsets in western regions and an increased desynchrony between our body clocks and the clock time.
Sleep/wake cycles, hormone release, temperature and metabolism, among others, operate on circadian rhythm. Our internal body clock runs on a slightly slower cycle and requires a daily reset through exposure to sunlight to stay on time.
Adopting permanent GMT would maintain
morning daylight before work and ensure
sufficient evening light during summer.
Winter sunlight challenges circadian rhythms
Exposure to sunlight following sleep is not a problem during the summer but can become a problem in winter where sunrise occurs in London just after 8 am in late December and later than 8.45 am in Glasgow. With society still centred around a 9 am work/school start time, most people will have exposure to daylight and the chance to reset their internal clock before starting work.
Historically, Daylight Saving Time (DST) was designed to allow more waking hours spent in daylight and possibly productive work (especially outdoor/agricultural). With workforces and lifestyles increasingly based indoors, this is less of a consideration today.
The downside of clock changes is that they move all our activities by one hour overnight, including sleep, disrupting our circadian rhythms and impacting health (such as a 24% increase in heart attacks on the Monday after the clock changes).
Advocating for permanent GMT
One proposal to remove these twice-yearly circadian jolts has been to adopt permanent DST. While more light in the evenings and all-year ‘summertime’ sounds attractive, it would create a serious issue for the morning circadian reset. Workers in Glasgow, for example, may not see any sunlight at all during December days when the sun rises and sets while they are still at work.
Adopting permanent GMT would maintain morning daylight before work and ensure sufficient evening light during summer for outdoor activities to remain mostly unaffected.
The British Sleep Society advocates for permanently adopting GMT to enhance the UK’s health and wellbeing, mitigate the adverse effects of biannual clock changes and maintain stable sleep patterns year-round.
