Human beings don’t like change. As a species, we’re a conservative bunch – very adaptable, of course, but ultimately fond of safe, predictable stasis. So it’s odd that twice a year, every year, we inflict a big, fundamental change upon ourselves when we turn our clocks back in autumn and forward in spring.
On paper, this biannual gear shift doesn’t seem that significant – it’s only an hour after all. But our bodies really don’t like change. The negative effects on our wellbeing are such that many health researchers believe the Sun needs to set on daylight saving time (DST) altogether.
Their reasoning? The clocks inside our bodies aren’t as easy to change as the ones on our walls. Mounting research shows that artificially altering the time twice a year has a significant impact on our circadian health, interrupting the rhythm of the internal body clocks that keep many of our bodily functions ticking.
When the clocks spring forward in March, for example, there’s usually a 25-per-cent uptick in the number of heart attacks reported. It’s thought disruption to our circadian clocks raises our blood pressure and the amount of cortisol, a stress hormone, in our systems, increasing the overall risk of a heart attack.
Other research suggests that circadian disruption interferes with our immune response, with the number of natural killer cells a person has falling when their body clock is knocked out of sync. When we gain an hour in October, the sudden onset of darkness also takes a toll.
“Particularly among people of European ancestry, there are those individuals who suffer from seasonal affective disorder,” says Dr John O’Neill, who studies circadian rhythms at the Medical Research Council Laboratory of Molecular Biology.
“That’s thought to be due to the times you see light. When you perceive that the day length is shorter, it signals you to be less active and this tends to lead to a lower mood.”
There’s also an increase in road traffic accidents. In 2019, the Royal Society for the Prevention of Accidents called for the UK government to abolish DST to reduce road fatalities and injuries. Lost sleep and dark driving conditions don’t help, but our circadian health is, again, a factor.
“The circadian clock regulates how able we are to maintain concentration and vigilance,” O’Neill says. “When the clocks go back, for a few days before the circadian clock has adjusted, people are going to be doing the same thing that they would have been doing previously, but an hour earlier. They’ll be that little bit more sleepy on the road.”
For O’Neill, DST isn’t worth it. “The consensus among circadian and sleep scientists is to abolish putting the clocks forward and back,” he says. “There’s not a strong enough argument for putting people through the stress of advancing and delaying the circadian clock.”
Backwards thinking
So why does the UK, and around 70 other countries around the world, do it? Daylight saving time, as the name suggests, is designed to make the most of the daylight hours as the seasons change.
Sometimes erroneously credited to the American inventor and statesman Benjamin Franklin, a form of daylight saving can be traced back to Roman times. It was the New Zealand entomologist George Hudson and the English builder William Willett who independently proposed that there should be state-level changes to timekeeping around the turn of the 20th century.
Germany was the first country to formally adopt it, in 1916, with Britain and several other European nations following soon after. Productivity and energy conservation for the war effort were the two principal reasons behind daylight saving.
By changing the clocks to maximise evening light, Willett and others argued that the economy would benefit from more people working for longer during the daylight hours, while energy and money would also be saved on street lighting.
Of course, the way we use energy has changed dramatically in a century, and a 2017 meta-analysis in The Energy Journal found that DST generates electricity savings of just 0.3 per cent in today’s world.
There are other reasons to enjoy British Summer Time though. Proponents point to the extended evening sunshine, which allows people to engage in hobbies, socialise and exercise later in the day, which also helps to keep the economy moving – or does it?
Research published this year by health economists at the London School of Economics says that, overall, we’re worse off because of DST, both in terms of wealth and wellness. When the clocks change in spring, as well as the increased risk of a heart attack and hospitalisation, researchers found wide-ranging detrimental effects.
The Monday after the clocks change, people work an average of 40 minutes longer. As well as lost sleep, their time stress rises and their leisure time falls. Overall life satisfaction drops by 1.44 per cent. If that doesn’t sound like much, the effect costs an estimated €750 per capita, according to the analysis.
That’s around £625 per person, and if you just take the working population of the UK (and a back-of-the-envelope calculation), that amounts to a cost of roughly £20.6bn to the British economy.
Time for change
Joan Costa-i-Font, professor of health economics at the London School of Economics, led the research.
It’s essentially a huge cost-benefit analysis, he says, and even though there are some benefits in the autumn when we have that extra hour – such as a fall in the reported number of heart attacks, compared with the rise in the spring – his conclusions are clear.
DST costs us, both as individuals and as a society. “We’re losing out,” he says. “There are slight positive effects in October when people get an hour more sleep, but the net effect is detrimental.”
Globally, there’s a dawning realisation that changing the clocks twice a year does more harm than good. The US Senate has proposed a law that would signal a shift to a permanent standard time.
The European Parliament has also proposed ending daylight saving. In the UK, the Daylight Saving Bill of 2010-2012 failed to pass the House of Commons, but researchers and other advocates are still campaigning for it.
So why do the clocks still change? “There’s consensus that changing the time isn’t great,” Costa-i-Font says. “But which time zone should we adjust to? That’s where we don’t have agreement. There is, for example, a big north-south divide in Europe.”
Similar debates exist within the UK. The majority of researchers prefer a permanent shift to British Summer Time, making the most of those lighter evenings. But that would come with darker winter mornings, especially across the north of the country, and some question the safety implications for morning commutes and school runs during those months of the year.
“Controlling the time is always political,” according to Costa-i-Font. “Politicians and decision-makers don’t want to be blamed or step up and set one particular time because they know that they will antagonise 30 per cent of the population.”
Even so, he hopes that there’s now enough political momentum that the lights will soon go out on daylight saving. So you might want to make the most of that extra hour in bed you’ll get at the end of this month. It could be the last time it happens.
About our experts
Joan Costa-i-Font is a professor of health economics at the London School of Economics. He is a faculty associate of LSE Health and the International Inequalities Institute, where he leads the Ageing and Health Incentives Lab (AHIL) and co-leads the perceptions of inequality program.
Dr John O’Neill, works at the Medical Research Council Laboratory of Molecular Biology. His specialities lie in cellular rhythms, signalling and metabolic regulation.
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