Authors: Anna Goodman, James Paskins, and Roger Mackett
ABSTRACT
Background: Children in primary school are more physically active in the spring/summer. Little is known about the relative contributions of day length and weather, however, or about the underlying behavioral mediators. Methods: 325 British children aged 8-11 wore accelerometers as an objective measure of physical activity, measured in terms of mean activity counts. Children simultaneously completed diaries in which we identified episodes of out-of-home play, structured sports and active travel. Our main exposure measures were day length, temperature, rainfall, cloud cover and wind speed. Results: Overall physical activity was higher on long days (≥14 hours daylight), but there was no difference between short (<9.5 hours) and medium days (10.2-12.6 hours). The effect of long day length was largest between 17:00 and 20:00, and persisted after adjusting for rainfall, cloud cover and wind. Up to half this effect was explained by a greater duration and intensity of out-of-home play on long days; structured sports and active travel were less affected by day length. Conclusions: At least above a certain threshold, longer afternoon/evening daylight may have a causal role in increasing child physical activity. This strengthens the public health arguments for daylight saving measures such as those currently under consideration in Britain.
Keywords: youth, seasonal variation, public health, daylight
Acceptance Date: October 1, 2011
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