Actigraph-defined moderate-to-vigorous physical activity cut-off points among children: statistical and biobehavioural relevance
Article first published online: 9 JAN 2009
©2008 The Author(s)/Journal Compilation ©2008 Foundation Acta Pædiatrica/Acta Pædiatrica
Volume 98, Issue 4, pages 708–714, April 2009
How to Cite
Guinhouya, C. B., Lemdani, M., Vilhelm, C., Durocher, A. and Hubert, H. (2009), Actigraph-defined moderate-to-vigorous physical activity cut-off points among children: statistical and biobehavioural relevance. Acta Paediatrica, 98: 708–714. doi: 10.1111/j.1651-2227.2008.01187.x
- Issue published online: 6 MAR 2009
- Article first published online: 9 JAN 2009
- Received 23 May 2008; revised 26 October 2008; accepted 25 November 2008.
- Measurement error;
Aim: To compare Actigraph-defined moderate-to-vigorous physical activity (MVPA) cutpoints among children, combining statistical and biobehavioural analyses.
Methods: One hundred and thirteen children aged 10.0 ± 0.8 years wore accelerometer for three days. The time they spent in MVPA was estimated using 10 thresholds ranged from 3000 to 3900 cpm. A statistical construct including 45 Bland and Altman pairwise analyses was used to compare the 10 estimates of MVPA. A regression was performed to develop an equation relating mean differences to the between-cutpoint gaps.
Results: Mean differences in the MVPA estimates ranged from 1.6 to 12.8 min as a function of increment. Raw estimates of MVPA decreased according to an arithmetic sequence with a common difference of 200 cpm. This difference translates into a drop of 12% in MVPA and a misclassification of up to 5% of children. Mean differences (Y) could be predicted from increments (X) using: Y= 0.02 X (R2= 0.99, SEE = 0.72, p < 0.0001).
Conclusion: When a lack of agreement should be assumed as the between-cutpoint gap exceeds 200 cpm, statistical differences may occur earlier at 90 cpm. Yet, the current equation makes it possible to compare and adjust results from studies/interventions using diverse cutpoints for MVPA among children.