One hour. That’s all the clock change takes, and yet your body can feel it for days. Your sleep, your energy and even your heart need time to adjust. Here’s our advice to keep you in rhythm.
Saving daylight, losing sleep: the real cost of the clock change
Suddenly it is still pitch-dark when you wake up or it feels like you are leaving from work hours later than usual. The switch to winter time (the last Sunday in October) and summer time (the last Sunday in March) feels unnatural. Which it is. The decision was taken on purely economic grounds.
During the industrial revolution, the idea emerged of saving energy by making the most of natural daylight for longer. It was the severe oil crisis which prompted the European Union to effectively introduce the alternating winter and summer time in 1977. Today, 1.5 billion people in more than 70 countries around the world change their clocks twice a year.
Literally thrown off beat
Moving the clock one hour forward or back disrupts your biological rhythm more than you might expect. In the weeks after the change, many people have trouble falling asleep, wake up during the night, or feel like they have mild jet lag.
Poor sleep also affects concentration. You may notice it in small ways: bumping into things, dropping things, or losing focus on your way to work.
Research shows the effects go further. In the week after the change, road traffic accidents increase, and fatigue-related incidents at home and at work rise as well.
But material damage is not the biggest concern, as the clock change may also affect your heart rhythm.
Does the clock change affect your heart?
Your disrupted body rhythm not only temporarily sabotages your concentration and coordination, it can also have an impact on your blood pressure and heart rhythm.
Sleep problems trigger heart rhythm disorders. That is a proven fact we have known about for longer than today. But recent scientific research shows a clear link between seasonal clock changes and heart problems. Finnish researchers discovered that the risks of stroke and sleep apnea (in which your breathing stops for at least 10 seconds during sleep) are noticeably greater during the time after the switch.
Summer time versus winter time
Stroke rates rise in the days right after the clock changes. But is there a difference between spring and autumn? In spring we lose an hour, so in autumn we gain one, right?
Not quite. Research shows you lose sleep either way. Sleep quality matters as much as sleep quantity. In spring you lose an hour of sleep. In autumn, the shift disrupts your deep sleep, even if the extra hour feels pleasant.
Still, hospital admissions for stroke rise most after the spring change. Losing an hour puts more immediate stress on the body than gaining one.
The effects of the autumn change are thought to be more subtle and gradual. Winter is also the season when the most heart rhythm disorders are recorded, partly because of less daylight and colder temperatures.
Are women more sensitive to the clock change?
Splitting the figures by sex reveals a clear difference: women appear to be more affected by the clock change than men. Why that is remains unclear. Hormones may play a role, but more research is needed. Either way, if you’re a woman, it’s worth paying a bit more attention to rest and sleep in the weeks around the clock change.
The conclusion
The economic benefits of the clock change are unproven, while the health effects are well documented. For years, many have called for an end to the twice-yearly switch. The European Parliament voted in favour of ending it in 2019, but EU member states still have to agree, including on whether to keep summer or winter time permanently.
Until then, the best you can do is make the switch as easy as possible for your body.
Tip 1: Shift your rhythm gradually
Start a few days before the clock change and adjust your bedtime in steps of 15 minutes:
- Autumn (clocks go back): go to bed 15 minutes later three days before, 30 minutes later two days before, and 45 minutes later the day before.
- Spring (clocks go forward): do the same, but go to bed earlier each day.
Can’t fall asleep when you go to bed earlier? Help your body produce melatonin, the sleep hormone. Dim the lights in the evening, avoid screens, and wind down with a book or a warm bath.
Tip 2: Keep a regular sleep rhythm all year
If you’re already short on sleep, the clock change hits harder. Go to bed at roughly the same time every night and make sure you get enough sleep, not just around the clock change.
Tip 3: Keep an eye on your heart rhythm
Want to know how your heart rhythm is doing during this period? With FibriCheck, you can measure it with your smartphone and get the result within a minute. If you feel palpitations or notice something unusual, take a measurement and talk to your doctor if you’re concerned.
References
- Harrison Y. The impact of daylight saving time on sleep and related behaviours. Sleep Med Rev. 2013 Aug;17(4):285-92.
- Sipilä JO, Ruuskanen JO, Rautava P, Kytö V. Changes in ischemic stroke occurrence following daylight saving time transitions. Sleep Med. 2016 Nov-Dec;27-28:20-24.
- Chudow JJ, Dreyfus I, Zaremski L, Mazori AY, Fisher JD, Di Biase L, Romero J, Ferrick KJ, Krumerman A. Changes in atrial fibrillation admissions following daylight saving time transitions. Sleep Med. 2020 May;69:155-158.