Day Length and Weather Effects on Children's Physical Activity and Participation in Play, Sports and Active Travel

Background/Aims Proponents of the Daylight Saving Bill currently under consideration in the UK parliament have hypothesised that extending afternoon daylight would promote child physical activity. Our aim was to investigate the relative contribution of day length and weather to children’s physical activity, and the behavioural mediators underlying these effects.

Methods In 2002-2006, 325 British children (8-11 years, 170 girls) wore accelerometers (964 days of valid data) and completed activity diaries (995 days). Our primary outcome was time in moderate-to-vigorous physical activity (MVPA).

Results Time in MVPA 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.

Conclusion At least above a certain threshold, longer afternoon/evening daylight appears to have a causal role in increasing child physical activity. This strengthens the public health arguments in favour of daylight saving measures such as those currently under consideration in Britain.