clock change and stroke risk
Clocks in the UK will go forward by one hour on the last Sunday in MarchDineshraj Goomany/ Flickr creative commons

Clocks in the UK will jump forward by one hour at 1am on the last Sunday in March, as the UK enters a period called British Summer Time. From Sunday 27 March, there will be more daylight in the evenings and less in the mornings. This is also known as Daylight Saving Time.

British Summer Time was first established by the Summer Time Act in 1916. When the clocks go back in October, the UK is on Greenwich Mean Time.

When did we start changing the clocks?

BST was established after a campaign by a builder called William Willett, who was allegedly annoyed with the waste of daylight in the early mornings of summer. He suggested the change in 1907 in a leaflet called The Waste of Daylight. One year after Willett's death, BST was introduced in May.

The UK has not always changed its clocks. During the Second World War in 1940, clocks across Britain were not put back an hour at the end of British Summer Time in a bid to save fuel and money. In subsequent years, clocks continued to be moved forward by one hour every spring, and put back by an hour each autumn until July 1945. During this time, the UK was two hours ahead of GMT – a period called British Double Summer Time.

clocks go back change 2015
Studies suggest changing our clocks can lead to health problemsGetty

What are the benefits?

Some claim the clock change helps end the gloomy winter weather and reduce the symptoms of Seasonal Affective Disorder (SAD) with the extra hour of sunlight. Other suggest there could be economic benefits from bringing the UK in line with the same time zone as most of its European counterparts. The lighter evenings are also believed to reduce the number of road traffic accidents, although this is disputed.

What are the downsides of British Summer Time?

The disruption of changing the clocks leads to a risk of being late for an event, but more significantly, some say putting the time forward can be economically and socially disruptive.

There are also alleged health risks, such as increasing the risk of stroke. Researchers from the University of Turku in Finland have shown that the rate of the most common form of stroke, ischemic stroke, is higher in the two days following a daytime saving light transition.