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Time check: moving to the light side could improve health

Lighter evenings are related to higher physical activity levels in children and young people, according to new research in the open access International Journal of Behavioral Nutrition and Physical Activity this week. The research suggests that proposals to permanently increase the hours of waking daylight could deliver health benefits.

More than 23,000 children aged 5-16 years in nine countries: England, Australia, USA, Norway, Denmark, Estonia, Switzerland, Brazil and Madeira, Portugal – wore accelerometers to measure body movement. Researchers from London School of Hygiene and Tropical Medicine and the University of Bristol looked at their physical activity levels in relation to the time of sunset and found that their total daily activity levels were 15-20 per cent higher on summer days where the sun went down after 21.00 compared with winter days when it was before 17.00.

Around the world there are various proposals to shift the clocks forward by an additional hour year round. This was discussed in the British Parliament between 2010 and 2012, with proposals that would have seen British children enjoying an estimated 200 extra waking daylight hours per year. Australian states have also held referenda, and there was even a single-issue political party ‘Daylight Saving for South East Queensland’ in 2008.

The research suggests that additional daylight savings measures would lead to an average of two extra minutes of moderate-to-vigorous physical activity per child per day. With children accumulating an overall average of 33 minutes a day of this type of activity, an additional two minutes represents around a five per cent increase. This may sound modest but the researchers argue that it represents a non-trivial step in the right direction.

These effects also appeared to be broadly equitable, applying to girls as well as to boys; to overweight and obese children as well as to normal weight children; and to children from different socioeconomic backgrounds.

Anna Goodman, lead author from London School of Hygiene & Tropical Medicine, said: “This study provides the strongest evidence to date that, in Europe and Australia, evening daylight plays a role in increasing physical activity in the late afternoon and early evening – the ‘critical hours’ for children’s outdoor play. Introducing additional daylight savings measures would affect each and every child in the country, every day of the year, giving it a far greater reach than most other potential policy initiatives to improve public health.”


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Notes to editor:
1. Research article
Daylight saving time as a potential public health intervention: an observational study of evening daylight and objectively-measured physical activity among 23,000 children from 9 countries
Elisa Giannetta, Tiziana Feola, Daniele Gianfrilli, Riccardo Pofi, Valentina Anna Goodman, Angie S Page and Ashley R Cooper
International Journal of Behavioral Nutrition and Physical Activity 2014, 11:84

The article is available at journal website here.

Please name the journal in any story you write. If you are writing for the web, please link to the article. All articles are available free of charge, according to BioMed Central's open access policy.

2. International Journal of Behavioral Nutrition and Physical Activity (IJBNPA) is an open access, peer-reviewed online journal devoted to furthering the understanding of the behavioral aspects of diet and physical activity.

3. BioMed Central is an STM (Science, Technology and Medicine) publisher which has pioneered the open access publishing model. All peer-reviewed research articles published by BioMed Central are made immediately and freely accessible online, and are licensed to allow redistribution and reuse. BioMed Central is part of Springer Science+Business Media, a leading global publisher in the STM sector.