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

the International Childrens Accelerometry Database(ICAD)

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Abstract

Background: It has been proposed that introducing daylight saving measures could increase childrens physical activity, but there exists little research on this issue. This study therefore examined associations between time of sunset and activity levels, including using the bi-annual changing of the clocks as a natural experiment. Methods: 23,188 children aged 5-16 years from 15 studies in nine countries were brought together in the International Childrens Accelerometry Database. 439 of these children were of particular interest for our analyses as they contributed data both immediately before and after the clocks changed. All children provided objectively-measured physical activity data from Actigraph accelerometers, and we used their average physical activity level (accelerometer counts per minute) as our primary outcome. Date of accelerometer data collection was matched to time of sunset, and to weather characteristics including daily precipitation, humidity, wind speed and temperature. Results: Adjusting for child and weather covariates, we found that longer evening daylight was independently associated with a small increase in daily physical activity. Consistent with a causal interpretation, the magnitude of these associations was largest in the late afternoon and early evening and these associations were also evident when comparing the same child just before and just after the clocks changed. These associations were, however, only consistently observed in the five mainland European, four English and two Australian samples (adjusted, pooled effect sizes 0.03-0.07 standard deviations per hour of additional evening daylight). In some settings there was some evidence of larger associations between daylength and physical activity in boys. There was no evidence of interactions with weight status or maternal education, and inconsistent findings for interactions with age. Conclusions: In Europe and Australia, evening daylight seems to play a causal role in increasing childrens activity in a relatively equitable manner. Although the average increase in activity is small in absolute terms, these increases apply across all children in a population. Moreover, these small effect sizes actually compare relatively favourably with the typical effect of intensive, individual-level interventions. We therefore conclude that, by shifting the physical activity mean of the entire population, the introduction of additional daylight saving measures could yield worthwhile public health benefits.

Original languageEnglish (US)
Article number84
JournalInternational Journal of Behavioral Nutrition and Physical Activity
Volume11
Issue number1
DOIs
StatePublished - Oct 23 2014

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Observational Studies
Public Health
Exercise
Weather
Accelerometry
Insurance Benefits
Humidity
Population
Mothers
Databases
Education
Weights and Measures
Temperature
Research

All Science Journal Classification (ASJC) codes

  • Medicine (miscellaneous)
  • Physical Therapy, Sports Therapy and Rehabilitation
  • Nutrition and Dietetics

Cite this

@article{c82ef7595d3b49b38ea11397c091ab88,
title = "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",
abstract = "Background: It has been proposed that introducing daylight saving measures could increase childrens physical activity, but there exists little research on this issue. This study therefore examined associations between time of sunset and activity levels, including using the bi-annual changing of the clocks as a natural experiment. Methods: 23,188 children aged 5-16 years from 15 studies in nine countries were brought together in the International Childrens Accelerometry Database. 439 of these children were of particular interest for our analyses as they contributed data both immediately before and after the clocks changed. All children provided objectively-measured physical activity data from Actigraph accelerometers, and we used their average physical activity level (accelerometer counts per minute) as our primary outcome. Date of accelerometer data collection was matched to time of sunset, and to weather characteristics including daily precipitation, humidity, wind speed and temperature. Results: Adjusting for child and weather covariates, we found that longer evening daylight was independently associated with a small increase in daily physical activity. Consistent with a causal interpretation, the magnitude of these associations was largest in the late afternoon and early evening and these associations were also evident when comparing the same child just before and just after the clocks changed. These associations were, however, only consistently observed in the five mainland European, four English and two Australian samples (adjusted, pooled effect sizes 0.03-0.07 standard deviations per hour of additional evening daylight). In some settings there was some evidence of larger associations between daylength and physical activity in boys. There was no evidence of interactions with weight status or maternal education, and inconsistent findings for interactions with age. Conclusions: In Europe and Australia, evening daylight seems to play a causal role in increasing childrens activity in a relatively equitable manner. Although the average increase in activity is small in absolute terms, these increases apply across all children in a population. Moreover, these small effect sizes actually compare relatively favourably with the typical effect of intensive, individual-level interventions. We therefore conclude that, by shifting the physical activity mean of the entire population, the introduction of additional daylight saving measures could yield worthwhile public health benefits.",
author = "{the International Childrens Accelerometry Database(ICAD)} and Anna Goodman and Page, {Angie S.} and Cooper, {Ashley R.} and K. Kordas and R. Davey and Pate, {R. R.} and J. Salmon and Andersen, {L. B.} and K. Froberg and L. Sardinha and S. Anderssen and A. Timperio and Janz, {K. F.} and S. Kreimler and P. Hallal and {van Sluijs}, E. and Sutton, {G. P.} and U. Ekelund and L. Sherar",
year = "2014",
month = "10",
day = "23",
doi = "10.1186/1479-5868-11-84",
language = "English (US)",
volume = "11",
journal = "International Journal of Behavioral Nutrition and Physical Activity",
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TY - JOUR

T1 - Daylight saving time as a potential public health intervention

T2 - An observational study of evening daylight and objectively-measured physical activity among 23,000 children from 9 countries

AU - the International Childrens Accelerometry Database(ICAD)

AU - Goodman, Anna

AU - Page, Angie S.

AU - Cooper, Ashley R.

AU - Kordas, K.

AU - Davey, R.

AU - Pate, R. R.

AU - Salmon, J.

AU - Andersen, L. B.

AU - Froberg, K.

AU - Sardinha, L.

AU - Anderssen, S.

AU - Timperio, A.

AU - Janz, K. F.

AU - Kreimler, S.

AU - Hallal, P.

AU - van Sluijs, E.

AU - Sutton, G. P.

AU - Ekelund, U.

AU - Sherar, L.

PY - 2014/10/23

Y1 - 2014/10/23

N2 - Background: It has been proposed that introducing daylight saving measures could increase childrens physical activity, but there exists little research on this issue. This study therefore examined associations between time of sunset and activity levels, including using the bi-annual changing of the clocks as a natural experiment. Methods: 23,188 children aged 5-16 years from 15 studies in nine countries were brought together in the International Childrens Accelerometry Database. 439 of these children were of particular interest for our analyses as they contributed data both immediately before and after the clocks changed. All children provided objectively-measured physical activity data from Actigraph accelerometers, and we used their average physical activity level (accelerometer counts per minute) as our primary outcome. Date of accelerometer data collection was matched to time of sunset, and to weather characteristics including daily precipitation, humidity, wind speed and temperature. Results: Adjusting for child and weather covariates, we found that longer evening daylight was independently associated with a small increase in daily physical activity. Consistent with a causal interpretation, the magnitude of these associations was largest in the late afternoon and early evening and these associations were also evident when comparing the same child just before and just after the clocks changed. These associations were, however, only consistently observed in the five mainland European, four English and two Australian samples (adjusted, pooled effect sizes 0.03-0.07 standard deviations per hour of additional evening daylight). In some settings there was some evidence of larger associations between daylength and physical activity in boys. There was no evidence of interactions with weight status or maternal education, and inconsistent findings for interactions with age. Conclusions: In Europe and Australia, evening daylight seems to play a causal role in increasing childrens activity in a relatively equitable manner. Although the average increase in activity is small in absolute terms, these increases apply across all children in a population. Moreover, these small effect sizes actually compare relatively favourably with the typical effect of intensive, individual-level interventions. We therefore conclude that, by shifting the physical activity mean of the entire population, the introduction of additional daylight saving measures could yield worthwhile public health benefits.

AB - Background: It has been proposed that introducing daylight saving measures could increase childrens physical activity, but there exists little research on this issue. This study therefore examined associations between time of sunset and activity levels, including using the bi-annual changing of the clocks as a natural experiment. Methods: 23,188 children aged 5-16 years from 15 studies in nine countries were brought together in the International Childrens Accelerometry Database. 439 of these children were of particular interest for our analyses as they contributed data both immediately before and after the clocks changed. All children provided objectively-measured physical activity data from Actigraph accelerometers, and we used their average physical activity level (accelerometer counts per minute) as our primary outcome. Date of accelerometer data collection was matched to time of sunset, and to weather characteristics including daily precipitation, humidity, wind speed and temperature. Results: Adjusting for child and weather covariates, we found that longer evening daylight was independently associated with a small increase in daily physical activity. Consistent with a causal interpretation, the magnitude of these associations was largest in the late afternoon and early evening and these associations were also evident when comparing the same child just before and just after the clocks changed. These associations were, however, only consistently observed in the five mainland European, four English and two Australian samples (adjusted, pooled effect sizes 0.03-0.07 standard deviations per hour of additional evening daylight). In some settings there was some evidence of larger associations between daylength and physical activity in boys. There was no evidence of interactions with weight status or maternal education, and inconsistent findings for interactions with age. Conclusions: In Europe and Australia, evening daylight seems to play a causal role in increasing childrens activity in a relatively equitable manner. Although the average increase in activity is small in absolute terms, these increases apply across all children in a population. Moreover, these small effect sizes actually compare relatively favourably with the typical effect of intensive, individual-level interventions. We therefore conclude that, by shifting the physical activity mean of the entire population, the introduction of additional daylight saving measures could yield worthwhile public health benefits.

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