We’re some of the world’s leading experts – THIS is how the clocks going forward could affect you

An hour of sleep will be robbed from Brits on Sunday evening — all in the name of daylight savings. 

Despite gaining an extra hour of evening light, which encourages us to get outside and soak up much-needed vitamin D, there are a few downsides.

Experts believe the disruption and sleep loss may raise the risk of heart attacks and strokes.

The tradition, which is followed in most of Europe, the US and parts of Asia, has also been linked to a surge in car accidents. 

That’s not to mention the obvious bad mood caused by a lack of sleep.

Clocks have moved forward an hour every spring since WW1 in a bid for longer evenings and to conserve coal, before being reverted back at the end of October.

Here, MailOnline explores the science behind changing the clocks and your health — revealing some of the benefits and the downsides to altering the clocks.

Every spring at 1am on the last Sunday in March, we lose an hour of sleep to gain more evening light — a tradition that began in WW1, all in a bid for longer evenings and to conserve coal. Although it can be harder to get out of bed, you do get an extra hour of sunlight each evening

Mood boost

Losing an hour of sleep over the weekend may leave many grumpy.

But to make up for this, people can expect a mood boost over the summer months due to lighter evenings. 

‘Light elevates mood and reduces stress, so there might be some mood changes because of the extra light in the evening,’ says Professor Russell Foster, one of the world’s leading experts on the circadian rhythm, or the body’s internal clock, at the University of Oxford. 

Sunlight is important for the production of the feel-good hormone serotonin, according to the mental health charity Mind. 

The charity explains that when sunlight passes through the eye, it affects part of the retina that triggers serotonin production.  

Without exposure to sunlight your serotonin levels could drop, it warns.

Extra vitamin D

More daylight hours gives people more time to soak up evening sun.

This boosts levels of vitamin D — which the body creates from direct sunlight on the skin when outdoors.

Professor Foster warned that there is ‘a lot of evidence’ the people in the UK are vitamin deprived.

While Brits can get enough vitamin D from sunlight between late March and the end of September — during Daylight Savings Time (DST) — health chiefs recommend taking a supplement outside of this window. 

‘There are good sides to DST, such as coming home earlier (by the sun clock) from school or work and having more hours of daylight during our free time after work,’ writes Professor Till Roenneberg, in his article Why Should We Abolish Daylight Saving Time?

The sunshine vitamin is vital for bone health. 

Vitamin D helps to regulate the amount of calcium and phosphate in the body, according to the NHS. 

It is these nutrients that keep our teeth, bones and muscles healthy.

On top of this, having sufficient vitamin D levels has also been linked to a lower risk of depression.

More active in the evenings 

If the dark winter evenings stop you from going for a run or playing football, the extra hour of sunlight might just give you the time to get outside and be more active.

Professor Foster said: ‘With lighter evenings people are more likely to do more sports and they will do sport for longer. We can only encourage that.’

Adults between the ages of 19 and 64 should do at least 150 minutes of moderate intensity a week, such as brisk walking, dancing or riding a bike, or 75 minutes of vigorous intensity activity a week such as running or swimming. 

But having an extra hour of sunlight in the evening can motivate people get active outdoors, rather than lounging on the sofa, as tends to be done on winter evenings.

Studies have shown that children are more active when there is more daylight in the evenings.

The extra daylight hour gives more people the opportunity to get outside in the evenings for exercise

Social jet lag

While there are benefits to the clock change, it also leaves people more tired due to one less hour of sleep.

The clock change affects millions of people all at the same time which can have many negative consequences, says Dr Eva Winnebeck, a lecturer in chronobiology at the University of Surrey. 

She said: ‘For the months following the change, work and school schedules remain one hour earlier, and we must get up accordingly.

‘For many, this means rising before the sun again for the next weeks just like during the long nights of winter. 

‘This lack of morning sunlight can make it difficult for people to adjust their body clocks to the earlier schedules.’ 

This adjustment can cause a type of social jet lag where your natural body is not aligned with daylight saving time, Professor Roenneberg notes in his report on why we should abolish daylight saving time. 

Tiredness can lead to slowed thinking, worsened memory and mood changes, such as feeling more stressed, anxious or irritable.   

As well as battling sleepiness, the body may struggle to get to sleep and wake up following the clock change.  

Professor Foster added: ‘Morning light advances the clock and makes you get up earlier and evening light delays the clock and makes you get up later. 

‘More evening light versus morning light is probably going to shift the clock to a later time and make it more difficult to get up, which is a slight disadvantage.’ 

Increases risk of stroke 

Adjusting to the clock change might also raise the risk of physical health problems.

The combination of sleep deprivation and disruption to the circadian rhythm can, potentially, trigger a stroke. 

Professor Foster, who has penned a best-selling book on circadian rhythms, said 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.

Strokes can happen if the brain does not get a blood supply because the blood supply is cut off or restricted due to a blood clot, brain cells begin to die. Experts say the shift in time is enough to disrupt your circadian rhythm and trigger a stroke 

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.

In 2016, researchers investigating the link found an eight 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. 

But the risks are higher for some regions, experts say. 

Dr Winnebeck said: ‘Regions in the West of a time zone, where people have to rise earlier in relation to the sun, tend to show less sleep, lower incomes, lower health, higher cancer rates and more fatal traffic accidents.’

Car accidents

Springing the clocks forward has been linked to higher rates in car crashes. 

Fatal car accidents increased by 6 per cent in the US in the week after the shift to DST, according to a 2020 study by researchers at the University of Colorado. 

The findings suggest that 627 people died in crashes linked to the clock change between 1996 to 2017.

But Professor Russell Foster says the shift in time isn’t a health risk for everyone. 

He said: ‘It is important to emphasise that it is not for everybody. 

‘If you are vulnerable and you are already sleep deprived and you lose another hour, well that is going to have a big impact and you are more likely to have a crash. 

‘If you have hypertension or other illnesses, then that disruption will actually nudge you over the border.

‘But most of us should not be worrying about it particularly.’

He added: ‘For most of us who are healthy it is not going to have an impact, but it is in those of us that are vulnerable where the statistics will count.’

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. But, 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.