Salway, R;
Jago, R;
de Vocht, F;
House, D;
Porter, A;
Walker, R;
Kipping, R;
Owen, CG;
Hudda, MT;
Northstone, K;
et al.
Salway, R; Jago, R; de Vocht, F; House, D; Porter, A; Walker, R; Kipping, R; Owen, CG; Hudda, MT; Northstone, K; van Sluijs, E; International Children’s Accelerometry Database (ICAD) Collabora
(2024)
School-level intra-cluster correlation coefficients and autocorrelations for children's accelerometer-measured physical activity in England by age and gender.
BMC Med Res Methodol, 24 (1).
p. 179.
ISSN 1471-2288
https://doi.org/10.1186/s12874-024-02290-7
SGUL Authors: Owen, Christopher Grant
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Abstract
BACKGROUND: Randomised, cluster-based study designs in schools are commonly used to evaluate children's physical activity interventions. Sample size estimation relies on accurate estimation of the intra-cluster correlation coefficient (ICC), but published estimates, especially using accelerometry-measured physical activity, are few and vary depending on physical activity outcome and participant age. Less commonly-used cluster-based designs, such as stepped wedge designs, also need to account for correlations over time, e.g. cluster autocorrelation (CAC) and individual autocorrelation (IAC), but no estimates are currently available. This paper estimates the school-level ICC, CAC and IAC for England children's accelerometer-measured physical activity outcomes by age group and gender, to inform the design of future school-based cluster trials. METHODS: Data were pooled from seven large English datasets of accelerometer-measured physical activity data between 2002-18 (> 13,500 pupils, 540 primary and secondary schools). Linear mixed effect models estimated ICCs for weekday and whole week for minutes spent in moderate-to-vigorous physical activity (MVPA) and being sedentary for different age groups, stratified by gender. The CAC (1,252 schools) and IAC (34,923 pupils) were estimated by length of follow-up from pooled longitudinal data. RESULTS: School-level ICCs for weekday MVPA were higher in primary schools (from 0.07 (95% CI: 0.05, 0.10) to 0.08 (95% CI: 0.06, 0.11)) compared to secondary (from 0.04 (95% CI: 0.03, 0.07) to (95% CI: 0.04, 0.10)). Girls' ICCs were similar for primary and secondary schools, but boys' were lower in secondary. For all ages, combined the CAC was 0.60 (95% CI: 0.44-0.72), and the IAC was 0.46 (95% CI: 0.42-0.49), irrespective of follow-up time. Estimates were higher for MVPA vs sedentary time, and for weekdays vs the whole week. CONCLUSIONS: Adequately powered studies are important to evidence effective physical activity strategies. Our estimates of the ICC, CAC and IAC may be used to plan future school-based physical activity evaluations and were fairly consistent across a range of ages and settings, suggesting that results may be applied to other high income countries with similar school physical activity provision. It is important to use estimates appropriate to the study design, and that match the intended study population as closely as possible.
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Additional Information: | © The Author(s) 2024. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data. | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Keywords: | Adolescents, Children, Cluster autocorrelation, Cluster randomised trial, ICAD, Intra-cluster correlation coefficient, Physical activity, Sample size, Schools, Humans, Child, England, Accelerometry, Female, Male, Exercise, Schools, Cluster Analysis, Adolescent, Sex Factors, Age Factors, International Children’s Accelerometry Database (ICAD) Collaborators, Humans, Exercise, Cluster Analysis, Age Factors, Sex Factors, Schools, Adolescent, Child, England, Female, Male, Accelerometry, 1117 Public Health and Health Services, General & Internal Medicine | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
SGUL Research Institute / Research Centre: | Academic Structure > Population Health Research Institute (INPH) Academic Structure > REF 2021 user group |
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Journal or Publication Title: | BMC Med Res Methodol | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
ISSN: | 1471-2288 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Language: | eng | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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PubMed ID: | 39123109 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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URI: | https://openaccess.sgul.ac.uk/id/eprint/116741 | ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Publisher's version: | https://doi.org/10.1186/s12874-024-02290-7 |
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