Time for a change: Could additional daylight saving improve public health?

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football-478321_1280With the clocks going back in Europe this weekend, most of us will probably be looking forward to that extra hour in bed. But that joy of catching up on sleep is always short-lived, when throughout the winter we have to cope with longer, darker evenings.

In some countries, there have been intense debates on whether there should instead be permanent daylight saving, with the clocks shifted forward by an additional hour year round. A proposal known as “Single/Double Summer Time” could see the UK enjoying later sunsets, as it adopts the same time as mainland Europe, essentially GMT+1 hour in the winter and GMT+2 hours in the summer.

Supporters of the proposals say that the changes could lead to fewer road accidents, more leisure time, improved energy efficiency and boosts to the economy, while some early risers including laborers and farmers oppose the changes as they would have to face darker mornings. But now an additional argument has been brought to the table which may help win further support for the change.

New research published in International Journal of Behavioural Nutrition and Physical Activity has shown that having later sunsets may also lead to important public health benefits, through an increase in children’s physical activity.

The researchers from the London School of Hygiene & Tropical Medicine and the University of Bristol looked at data from over 23,000 children in nine countries (England, Australia, USA, Norway, Denmark, Estonia, Switzerland, Brazil and Madeira, Portugal) and studied the associations between the time of sunset and their physical activity levels, measured via waist-worn accelerometers.

They found that children’s total daily activity levels were up to 20% higher on summer days with sunset after 9pm, compared to winter days with sunset before 5pm. This was particularly the case in the European and Australian populations, and was observed even after the researchers adjusted for weather conditions and temperature. The authors say that this provides the strongest evidence to date that evening daylight plays a causal role in increasing physical activity in the late afternoon and early evening, which are the ‘critical hours’ for children’s outdoor play.

This new evidence could be important in contributing to ongoing political discussions around the introduction of additional daylight saving. A bill was debated in British Parliament between 2010 and 2012, with proposals which would have seen the UK population having an estimated 200 extra waking daylight hours per year. And several Australian states have also held repeated referenda on the topic, with the issue spawning the creation of the single-issue political party ‘Daylight Saving for South East Queensland’ in 2008. But so far no changes have occurred in either country.

The researchers estimate that additional daylight savings would lead to an average of two extra minutes of moderate-to-vigorous physical activity per child per day. While this difference might appear modest and may not compare to targeted initiatives that get children exercising and tackle obesity, the incredible potential of these proposals comes from how prevalent and widespread they could be throughout entire populations.

Not only were the effects on activity levels found to be broadly equitable, among girls and boys, obese children and normal weight children, and children from different socio-economic backgrounds, but introducing additional daylight savings measures would be a change that affects each and every child in the country, every day of the year. This means that it could have a far greater reach than most other potential policy initiatives to improve public health.

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Peter

There are lots of strong arguments for this – including that road traffic accidents are more likely on dark evenings (and not that much more likely on dark mornings – people are more alert/less tired in the mornings). The change doesn’t help, either, interfering with sleep patterns. It’s only a small effect on most individuals; but as a community, it adds up.

I have some sympathy with the idea of going over to continental time; but there’s another part of me that thinks that 12 O’clock should be noon (at least, for some point in the UK) – the point when the sun is at it’s highest, that clocks should reflect the real, natural world; and that rather than changing the clocks we should should change our routine working day to 8-4, instead of 9-5.

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