Additional Daylight Saving Could Improve Public Health

Researchers at the London School of Hygiene & Tropical Medicine (LSHTM; United Kingdom) and the University of Bristol (United Kingdom) reviewed 15 studies in nine countries that included 23,188 children (aged 5–16 years) to form the International Children’s Accelerometry Database. All children provided objectively measured physical activity data from Actigraph accelerometers. Accelerometer data collection was matched to time of sunset, and to weather characteristics including daily precipitation, humidity, wind speed and temperature.

The results showed that the children's total daily activity levels were 15%–20% higher on summer days with sunset after 21:00, compared to winter days with sunset before 17:00. This was particularly the case in the European and Australian populations. Of special relevance was the bi-annual changing of the clocks; the activity of 439 individual children measured on the days just before and just after the clocks changed revealed that the same child immediately became more active on the days where the sunset had been moved an hour later. The study was published in the November 2014 issue of the International Journal of Behavioural Nutrition and Physical Activity.

“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,” said lead author Anna Goodman, PhD, of the LSHTM. “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."

The researchers estimate that additional daylight savings measures, such as adding another hour year round, would lead to an average of two extra minutes of moderate-to-vigorous physical activity per child per day, a modest (but not trivial) addition to children's overall activity levels, which averaged at 33 minutes per day. The effects also appeared to be broadly equitable, applying to girls as well as to boys; to overweight/obese children as well as to normal weight children; and to children from different socioeconomic backgrounds.

Related Links:
London School of Hygiene & Tropical Medicine
University of Bristol