Dr Muiris Houston: Why it’s time the clocks stopped going back an hour

Are you looking forward to an extra hour of sleep next weekend?Or are you dreading the reduction in evening light that comes with the seasonal clock change?Wouldn’t it be easier if there was no biannual challenge to our circadian rhythms?In 2019 the European Parliament voted to end our seasonal clock change. But the initiative remains deadlocked in the Council of the European Union. Member states cannot agree on whether to stay on permanent standard time or to settle on year round daylight savings time. Lithuania, which takes over the EU presidency in January, has signalled it will try to resolve the issue next year.READ MOREElsewhere, there has been a concerted move towards permanent daylight saving time. In Canada, British Columbia, Alberta and the Northwest Territories adopted the policy this year. And in the US, the House of Representatives passed a Bill in July to establish permanent daylight saving time nationwide, although the measure remains before the Senate.[ Clocks will move back on October 25th for winter timeOpens in new window ]However, research just published in the Canadian Medical Association Journal (CMAJ) points to permanent standard time as the healthier option, because it keeps the clock more closely aligned with human circadian rhythm. The authors note that permanent daylight saving time would push sunrise an hour later. The extra hour of morning darkness could leave people travelling to work or school before sunrise during the winter, with consequences for sleep, mood, learning and productivity, they say. “Our biological clocks need morning light to stay synchronised with the 24-hour day,” said Simon Fraser University’s Prof Ralph Mistlberger, co-author of the study. “Permanent daylight saving time moves that light an hour later just when winter mornings are already darkest.”Our biological clocks follow a circadian rhythm, around (circa) which the day (dies) revolves. The circadian rhythm is an internal clock that makes the brain cycle between intervals of alertness and sleepiness. Circadian rhythms comprise various elements that influence these intervals, including eating habits, body temperature and duration of sleep, as well as external factors such as darkness and lightness.Our circadian rhythms actually run on a longer schedule than a full day – for 24.2 hours. For that reason we rely on natural sunlight to keep us synchronised with the world around us. Morning light is some of the most important, the authors note, because it jump-starts that rhythm, wakes us up and gets us moving. Evening light, on the other hand, delays the circadian rhythm, interfering with our sense of “social time” and making it tougher to get to sleep and wake up rested in the morning.Moving to daylight savings time in the spring is especially detrimental to our health. In a 2020 report in the journal PLoS Computational Biology, researchers identified a significant increase in fatal traffic accidents (up to 30 per cent on the day of commencing daylight savings time), a short-term rise in workplace injuries (up 5.7 per cent after the spring clock change as employees sleep 40 minutes less on average) and elevated rates of acute heart attacks (up by about 4 per cent).[ A good night’s sleep is a class issueOpens in new window ]The Canadian researchers acknowledge that adopting permanent standard time also has drawbacks. Earlier summer sunrises could cause problems for people prone to waking early, while earlier winter sunsets could limit evening outdoor and commercial activity. They recommend relatively modest measures such as blackout curtains and public education on sleep health to address those effects.Permanent daylight saving time, in contrast, would require a much broader set of measures to reduce the effects of darker winter mornings.These include better street lighting and pathways, improved traffic safety, reflective equipment for children, later school start times, flexible work schedules and increased morning lighting in schools and workplaces. There is broad agreement on the need to end our biannual clock changes. However, the health arguments for permanent standard time stand in stark contrast to an apparent societal preference for permanent daylight savings time.muiris.houston@irishtimes.com