Daylight savings time is bad for your health, researchers warn

5 Nov 2019

Image: © anaumenko/

While its days appear numbered in the EU, researchers warn of the implications daylight savings time could have on your health.

When it comes to daylight savings time (DST), the implications on your health can last a lot longer than gaining or losing an hour of sleep. Writing in a commentary piece in JAMA Neurology, researchers from Vanderbilt University Medical Center have warned that DST eliminates bright morning light essential for synchronising biological clocks.

This, they said, is associated with increased risk of heart attack and ischemic stroke, as well as other negative effects of partial sleep deprivation. Also, the average length of sleep shrinks by 15 to 20 minutes in adults during DST transition, potentially increasing the risk of accidents.

‘It’s not one hour twice a year. It’s a misalignment of our biologic clocks for eight months of the year’

“People think the one-hour transition is no big deal, that they can get over this in a day, but what they don’t realise is their biological clock is out of sync,” said Beth Ann Malow, professor of neurology and paediatrics in the Sleep Disorders division at Vanderbilt University Medical Center.

“It’s not one hour twice a year. It’s a misalignment of our biologic clocks for eight months of the year. When we talk about DST and the relationship to light, we are talking about profound impacts on the biological clock, which is a structure rooted in the brain. It impacts brain functions such as energy levels and alertness.”

The researchers cited a number of large epidemiological studies advocating for the ending of the practice of setting clocks either forward or back. Marlow added that some people may have more flexible circadian rhythms and adjust quicker than others, such as children with autism who may take weeks or months to adjust.

In March of this year, the EU Transport and Tourism Committee voted in favour of scrapping DST from 2021. However, in June, the Irish Government announced plans to oppose the EU ruling as it may result in Ireland and Northern Ireland having different time zones post-Brexit.

Colm Gorey was a senior journalist with Silicon Republic