Relationships between sleep duration, physical activity and body mass index in young New Zealanders: An isotemporal substitution analysis

Borja Del Pozo-Cruz; Nicholas Gant; Jesús Del Pozo-Cruz; Ralph Maddison

doi:10.1371/journal.pone.0184472

Relationships between sleep duration, physical activity and body mass index in young New Zealanders: An isotemporal substitution analysis

PLoS One. 2017 Sep 12;12(9):e0184472. doi: 10.1371/journal.pone.0184472. eCollection 2017.

Authors

Borja Del Pozo-Cruz¹, Nicholas Gant¹, Jesús Del Pozo-Cruz², Ralph Maddison³

Affiliations

¹ Department of Exercise Sciences, Faculty of Science, University of Auckland (Auckland, New Zealand). TAMAKI BUILDING 731 -, Level 3, Tamaki Campus Gate 1,St Johns, Auckland, New Zealand.
² Department of Physical Education and Sports, University of Seville (Seville, Spain), Pirotecnia s/n, Seville, Spain.
³ School of Exercise and Nutrition, Faculty of Health Sciences, Deakin University (Geelong, Australia), Burwood, Victoria, Australia.

Abstract

Background: The evidence regarding the unique effect of sedentary behaviour on obesity among children is unclear. Moreover, the effect of substituting sedentary behaviour with physical activity of different intensities on the body composition of children has received limited empirical study.

Objective: To examine the mathematical effects on Body Mass Index (BMI) of substituting sedentary behaviours with physical activities of different intensities on children and youth aged 5-14 years old in New Zealand.

Methods: Secondary analysis of accelerometer data from the National Survey of Children and Young People's Physical Activity and Dietary Behaviours in New Zealand (2008/09) was conducted. A total of 1812 children and youth aged 5-24 years provided accelerometer-derived data on daily sedentary time (SB), light intensity physical activity (LPA) and moderate to vigorous physical activity (MVPA). Sleep time was assessed with a validated computerised use-of-time tool. BMI was assessed using anthropometric measurements. Multiple linear regression models were used to examine the independent associations of SB, Sleep time, LPA, and MVPA on BMI. The isotemporal substitution approach was used to ascertain the mathematical effect of substituting each of the other behaviours on BMI. Analyses were stratified by age groups.

Results: SB showed a unique (inverse) association with BMI across all age groups (p<0.05) but 20-24 years (p>0.05). Similarly, MVPA was positively associated (p<0.001) across all age groups. Among age groups 5-9 years, 10-14 years and 15-19 years, the estimated impact of replacing 60 min/day of SB with the same amount of MVPA time resulted in decreased BMI for all age groups (p<0.001), ranging from -1.26 (5-9 years) to -1.43 units (15-19 years). Similar results were achieved when SB was replaced with LPA or sleeping time for children (5-19 years). In young people (age group 20-24), the impact of replacing 30 min/day of SB with MVPA resulted in an estimated -1 BMI units decrease (p<0.001).

Conclusion: MVPA and SB have a unique effect on BMI. Further, substituting SB with LPA or MVPA was associated with a favourable effect on BMI across all age groups; with MVPA having the strongest association.

MeSH terms

Adolescent
Body Mass Index*
Child
Exercise*
Female
Humans
Male
New Zealand
Obesity / epidemiology*
Sleep Hygiene*
Young Adult

Grants and funding

The current study was not specifically funded. However, The national survey was funded by Sport and Recreation New Zealand, the Ministry of Health, the Ministry of Education and the Ministry of Youth, and was managed by the Clinical Trials Research Unit (now the National Institute for health Innovation), The University of Auckland and Synovate. Professor Maddison was supported by a Health Research Council, Sir Charles Hercus Fellowship. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.