An extra hour in bed may leave you feeling fresh.
But, if experts are to be believed, there might be darker consequences when clocks go back later this month.
Every spring at 1am on the last Sunday in March, an hour of sleep is robbed from us in the name of daylight saving — a tradition that began in WW1, all in a bid for longer evenings and to conserve coal.
Times revert back, this year anyway, on Sunday, October 30 at 2am.
Although only temporary and described as being like jet lag, some sleep scientists fear the effects are much more severe than that.
Experts believe the disruption may raise the risk of heart attacks and strokes. It has also been linked to a surge in car accidents.
That’s not to mention the obvious bad mood caused by disrupted sleep, one of the most common collateral effects of tinkering with the time.
Here, MailOnline explores the science behind changing the clocks and your health.
Turning the clocks back can disrupt your body’s 24-hour clock and impact your sleep. This could lead a risk of strokes, heart attacks, a chronic lack of sleep and depression as illustrated in the image above
What are circadian rhythms?
Circadian rhythms are 24-hour cycles linked to your bodies internal clock.
These rhythms are found in many different organisms including flowers to help them open and close.
Nocturnal animals also use their circadian rhythm to keep them from leaving their shelter during the day.
In people, circadian rhythms coordinate the digestive system, regulate hormones and it controls your sleep-wake cycles.
How does it work?
All the 24-hour cycles throughout the body are connected to a master clock in your brain and at different times of the day it signals to regulate activity in your body.
During the day sunlight causes the brain to send awake signals to keep us alert and active.
At night, the master clock in the brain sparks the production of melatonin, a hormone that promotes sleep, and then keeps transmitting signals that help us stay asleep through the night.
When the body’s circadian rhythm is disrupted, from jet lag or shift work, the internal clock can struggle to make the body fall asleep, stay asleep and have a lie in.
Professor Russell Foster, of the University of Oxford, is one of the world’s leading experts on the circadian rhythm, or the body’s internal clock.
It sets the rhythms of our lives, affecting everything from how clearly we think and when our digestive systems are ready for food, to when our muscles are at their strongest.
During the day, sunlight causes the brain to send awake signals that keep us alert and active.
At night, the system — likened to that of the intricate mechanism inside a grandfather clock — sparks the production of melatonin, a hormone that promotes sleep.
The rhythm itself is also central to our metabolism, body temperature and hormone levels.
The clocks going back plays havoc with these processes, resulting in disruption to our sleeping pattern.
According to Professor Foster, who has penned a best-selling book on the topic, a combination of sleep deprivation and a disruption of the circadian rhythm can, potentially, trigger a stroke.
The increased risk is all down to the collateral effect of high blood pressure, in theory.
High blood pressure can cause blood clots to form and block blood flow in the arteries leading to the brain.
This causes brain cells to start dying, which triggers the tell-tale signs of a stroke, such as slurred speech and weakness down one side of the body.
Professor Foster said: ‘We have this clock, and it is fine tuning every aspect of our physiology and behaviour to the 24-hour light and dark cycle.
‘We see increased blood pressure ranking up. For example, between 6am and 12 noon there is a 50 per cent greater chance of having a stroke anyway.
‘If you are being forced to get out of bed even earlier you are putting more stress on the system, which means you are less adapted to cope.’
He added: ‘For most of us it is fine because we have got a healthy and robust metabolism, but where you are at an increased risk the transition to daylight savings time can essentially put extra stresses on our biology and makes us more prone to illnesses.’
Strokes happen when the blood supply to part of the brain is cut off. For the brain to function properly it needs oxygen and nutrients provided by blood. If the brain does not get this because the blood supply is cut off or restricted due to a blood clot, brain cells begin to die. This can lead to a brain injury and in some cases death
Dozens of studies support Professor Foster’s warnings.
In 2016, researchers investigating the link found an 8 per cent increase in stroke hospital admissions in the two-day window after the clocks went forward or back.
Results from the study, which looked at more than 15,000 people, also showed the risk was higher for over-65s.
Dr John O’Neil is an expert in circadian rhythms based in Cambridge, he researches the 24-hour cycle in everything from cells, yeast, and algae to humans (left). Professor Russell Foster, of the University of Oxford, is one of the world’s leading experts on the circadian rhythm. He has also written a book called ‘Life Time’, which explores the impacts of changing the clocks (right)
Dr John O’Neill is another leading expert in the complicated field of circadian rhythms.
Based at the Medical Research Council Laboratory of Molecular Biology in Cambridge, he studies the 24-hour cycle in everything from cells in a petri dish, to humans.
His decades’ worth of academia have suggested the stress caused by changing the clocks may increase the risk of heart attacks.
But he insists that changing the clocks only impacts your health on a minor scale, in a similar fashion as jet lag.
He said: ‘If circadian rhythms are disrupted chronically, for example in shift work, we know that is really bad for your health in the long term.
‘It is very rare that anyone drops dead from it, but the risk associated with doing shift work is the equivalent to smoking cigarettes.’
He added: ‘If you fly to the states, you have a few days of jet lag where you are more vulnerable to more adverse health events, but not that much more at risk.
‘That is what we see when you shift the clocks by an hour, it is just like getting an hour’s jet lag.
‘It is really such a modest challenge to your circadian system that the vast majority of people deal with it absolutely fine.
‘But because it is happening at the level of the population you can see a slight increase in the frequency of heart attacks.’
In the days following the change in clocks there could be 40 more heart attacks than usual, according to Dr O’Neil. He explained that even though the disruption in circadian rhythm causes a stress to the body, only people who are unhealthy or susceptible to heart conditions are at risk. Image shows a man clutching his chest in pain with heart attack symptoms
An American study focusing on whether daylight savings increases the risk of heart attacks found that was, indeed, the case.
There was a 24 per cent rise in the number of heart attacks observed after the clocks went forward, compared to other Mondays throughout the year.
But the figure decreased when the clocks went back an hour, according to the research published in 2013.
Although there is a risk of heart problems from changing the clocks back, Dr O’Neill says there is a higher risk in the transition to summertime.
He said: ‘The main problem with British summer time is that it increases the difference between the solar clock, which is what your biological clock will tend to lock onto, and the physical clock that determines our daily routine.’
But only people who are unhealthy or susceptible to heart conditions are at risk, he says.
On a population level in the UK, Dr John O’Neill claimed only an extra 30 to 40 heart attacks occur more than usual in the days following the change to BST.
The same science behind the slight uptick in strokes explains why there is a slight increase in heart attacks after the clocks change — high blood pressure.
The condition causes the coronary arteries serving the heart to slowly become narrowed from plaque — a build-up of fat, cholesterol and other substances.
Blood clots are more likely to form when this plaque build-up and hardens. Plaque and blood clots can disrupt the flow of blood through the heart muscle, starving the muscle of oxygen and nutrients and causing a heart attack.
Just as it can impact your physical health, changing the clocks and disrupting your sleeping pattern can knock your mental health, too.
Professor Foster highlighted that people who are susceptible to depression are at a higher risk of being struck down when they are sleep deprived.
He said: ‘There is evidence that depression is intimately linked with sleep deprivation.
‘If you are disrupting your sleep and getting less sleep and you are vulnerable, you are more likely to slide into that depressed state.
‘If you add a disrupter, such as sleep loss or circadian rhythm disruption, you are going to be more vulnerable to slide into a dangerous state, for example a severe mental illness such as schizophrenia and bipolar.’
He added: ‘If you are getting less sleep, the tired brain has a tendency to remember negative experiences but forget the positive ones.
‘Your world view with a lack of sleep will be distorted. Your whole view of the world may be a bit more negative.’
Changing the clocks both in spring and in the autumn can cause people who are already susceptible to slide into depression. A lack of sleep can have serious impacts on your mental health causing depression, seasonal affective disorder (SAD) and it can exaggerate symptoms of confusion Alzheimer’s. Image shows a woman depressed after struggling to sleep
How to adjust your routine when the clocks change
There are ways to prepare yourself for clocks falling back an hour at the end of October.
Gradually going to bed later can help you to shift your body clock.
Eating an hour later than you usually would, will also help you adjust your bedtime schedule.
Professor Foster said: ‘You need to be aware of potential consequences, if you have a danger of high blood pressure and heart issues you need to take it carefully and make sure you are not leaping out of bed and making it worse.’
He added: ‘You may want to go into work a bit later. If you are going in half an hour later and you change that over the week to 15 minutes, then it is going to be easier on the system.’
Dr O’Neil believes it is always important to keep good sleep hygiene and a regular routine.
He said: ‘The most important signals for your biological clock are the times when you see light verses darkness and the times when you eat verses fasting.
‘I always have the same advice for the clocks changing as for any other time of year, that it is good to try and keep a constant routine, so you see light at around about the same time each morning, you have breakfast at about the same time and at night-time you fast and ensure you do not see any bright lights.’
One 2018 study, published in The Lancet Psychiatry, found a disrupted body clock was linked with depression, bipolar disorder and other problems.
A separate study, released in the Journal of Sleep Research in 2020, also found that a lack of sleep can put us in a bad mood.
Researchers showed participants images of laughing or crying children after five nights of normal sleep and after five nights of restricted sleep.
They found those who had less sleep were more likely to have negative responses to the images.
The symptoms of Alzheimer’s can become worse when the clocks spring forward and fall back, some experts believe.
Professor Foster explained the phenomenon in his book ‘Life Time’, which explores the impacts of changing the clocks.
He writes that clinical staff have noticed the ‘sundowning’ symptoms, which refers to a state of confusion, anxiety, aggression, pacing or wandering which occurs in the evening and early night, are worse when the clocks change.
The reasons why sundowning happens is not well understood.
But the Alzheimer’s Society says it may be down to tiredness, hunger, pain, a lack of sunlight during the day and disturbance to a person’s body clock from damage to the brain over time.
Seasonal affective disorder (SAD)
When the clocks fall back an hour, we start to see darker evenings as we enter the colder winter months.
Fewer daylight hours in the northern hemisphere can lead to ‘winter depression’, or seasonal affective disorder (SAD).
The symptoms are similar to depression and include a persistent low mood and difficulty concentrating.
It is thought one of the causes of SAD is disruption to your body’s internal clock.
Your body uses sunlight to time various important functions, such as when you wake up, so lower light levels during the winter may disrupt this and lead to symptoms of SAD, according to the NHS.
The extra hour in bed after the clocks fall back has been linked to an increase in car crashes as drivers adapt to the darker evenings.
That is according to research by Zurich insurance.
It analysed thousands of claims between 2018 and 2020 and found that prior to the autumn clock change, a quarter of car accidents occurred between 4-7pm.
This increased to almost a third of all crashes in November after the clocks have changed, leading them to blame the change in clocks.
However, the RAC Foundation suggests that the cold, rainy and darker evenings are to blame for this marvel rather than drivers being fatigued.
Research has revealed a shocking increase in car crashes after the clocks are turned back an hour in the autumn. Insurance company Zurich analysed thousands of car insurance claims between 2018 and 2020 and found that after the autumn clock change car accident increase by a third. Image shows a man falling asleep at the wheel of his car
Why do we switch the clocks back?
‘Spring forward, fall back’ is a well-known saying when it comes to daylight saving.
But why do we bother to change the clocks twice a year?
When do the clocks change?
In Spring, the clocks move an hour forward for British Summer Time (BST), to make the most of the daylight hours.
In autumn when the clocks go back the UK reverts to Greenwich Mean Time (GMT).
The UK is not alone, as a similar process happens in the US.
Is that how it’s always been?
In the early 1900s the clocks were always set to GMT, meaning in the summer it was light by 3am and dark at 9pm in the UK.
That was until people started to campaign for longer daylight hours to improve public health.
Change was sparked following the relentless pursuit of a builder in the 1900s.
William Willett began campaigning for change in 1905 after he noticed how many curtains were still drawn in the early hours of the morning in the summer.
In 1908 he won the support of the MP Robert Pearce after he published his leaflet ‘The Waste of Daylight’ calling for the time change.
However, the concept of rolling time back and forward was not formally introduced until the First World War, when war time coal shortages made the idea to introduce daylight saving more relevant.
During the war daylight saving allowed people to enjoy more hours of sunlight meaning there was less demand for coal-powered lighting. This left more coal to fuel the navy, railways and armaments industry.
In Spring the clocks move an hour forward for British Summer Time (BST), to make the most of the daylight hours. In autumn when the clocks go back the UK reverts to Greenwich Mean Time (GMT). The clocks will go back on Sunday, October 30 at 2am
Have we ever rolled the clocks back even further?
In the Second World War, Double British Summer Time was introduced. It was two hours in advance of GMT and was introduced to replace daylight saving.
During the winter, clocks were kept one hour in advance of GMT to increase public productivity.
After the war, the UK returned to BST apart from an experiment between 1968 and 1971 that saw the clocks put forward, but not back.
The experiment was discontinued, and the clocks were rolled back to GMT as it was found impossible to work out whether it had any benefit on society.
Why do people still want daylight savings time?
Advocates for the system claim the longer summer evening make people more active, reduce car accidents and save energy.
It is also argued that if the UK had one standard time all year round, it could mean farmers in Scotland would work for a couple hours in the dark during the winter.
It would also mean that children in the north of England and in Scotland would be forced to travel to and from school in the dark.
Are there calls to get rid of the clock changes?
There have been attempts to get rid of daylight saving.
Backbench MPs attempted to change BST to a permanent summer time but The Daylight Saving Bill 2010-12 was not passed by the House of Commons.
Some American states are also pushing to scrap changing the clocks. Arkansas, Delaware, Maine, Oregon, Tennessee and Washington have all ditched changing the clocks for a permanent daylight saving time.
Where else in the world changes the clocks?
Less than half of the countries in the world change the clocks to implement daylight saving, but more than 140 countries have applied it at some point.
The majority of European countries still make the switch twice a year.
In 2019, the European parliament voted to scrap daylight saving time, meaning they would no longer change the clocks twice a year. Yet, the change is yet to happen.
Parts of Australia, New Zealand, most of Mexico, Argentina, Paraguay, Cuba, Haiti, the Levant and Iran still change the clocks to save daylight hours.
And only two states in America, Arizona and Hawaii, have ditched the daylight saving in favour of a permanent winter time.