Time for a change? amriphoto/getty

Are you feeling tired today? Much of the UK got up an hour earlier than usual this morning, following the start of daylight savings. But there’s evidence that the clocks changing can have much more serious effects too, including heart attacks and strokes.

There’s little doubt that British Summer Time (BST) brings benefits, including reducing energy usage nationwide by allowing us to make better use of daylight hours. This has led to repeated calls for BST to last all year round, to cut carbon emissions and let us enjoy more of the country’s limited winter afternoon sunshine.

The act of switching to daylight savings every year also seems to harm some people’s health. Studies have found an annual spike in heart attacks in Michigan in the US and strokes in Finland the day after the clocks go forward in spring. Many of these deaths are likely to have been in frail, elderly people who are at the mercy of care staff schedules. But some could be due to loss of sleep: there’s evidence that heart attacks are most common on Mondays, possibly due to sleep lost while readjusting to the schedule of the working week.


The UK has tried year-round BST. The result was a large reduction in road casualties between 1968 and 1971, thanks to the lighter evenings, but the experiment was ended due to complaints from northern parts of the UK, where mornings were darker as a result.

Even more daylight

Many would like to see year-round BST reinstated. Some would even like to see our clocks pushed a further hour ahead in the summer, with the UK moving to the same time zone as Spain, which sits on the same line of longitude. According to a 2010 analysis, such a move would give people in Birmingham an extra 301 hours of after-work sunlight each year. People around Glasgow and Edinburgh would get 175 extra hours, and even people as far north as Aberdeen should gain 159 hours. It is also likely to reduce the nation’s carbon footprint by about 2.2 per cent as people would need to use less electricity for lighting in the evenings, when they tend to be more active than in the early mornings.

Calls for year-round BST are championed by the Royal Society for the Prevention of Accidents, which says the move will reduce road deaths currently caused by darker evenings in autumn and winter. But several petitions pushing for change have failed, so the debate looks set to continue.

In the meantime, be careful: if you’re suffering from a loss of sleep, it may affect your work. A recent study found that US federal judges mete out harsher sentences the day after the spring clock change, although we’ve previously noted that such studies should be taken with a pinch of salt.

Rest assured though that the physiological disruption from the clock change is short-lived. Our internal body clocks soon recalibrate, adjusting to our shifted sleeping and eating habits. But if you want to minimise the effects of switching to daylight savings next year, try going to sleep a little earlier each day in the run-up to the spring clock change.