Assessing 24-h movement behaviors in early childhood (0–4 years): Reliability of the My Little Moves app and comparison with accelerometry

Abstract Background The reliability and validity of proxy-report tools such as the My Little Moves (MLM) app for assessing 24-h movement behaviors (physical activity (PA), sedentary behavior (SB) and sleep) is insufficiently established in early childhood. We aimed to: (1) determine the minimum reporting time (number of hours and days of reported activities) required to reliably assess 24-h movement behaviors of 0–4-year-old children using the MLM app; and (2) evaluate the ability of the MLM app to assess PA, SB, and sleep by hypotheses testing of expected accelerometer-derived accelerations. Methods We used data from the MLM study, with at least two days of app data available for 324 children (22.0 ± 12.0 months, 48.3% girls), and accelerometer data (two Axivity AX3 devices, placed on wrist and hip) for 75 children (20.5 ± 11.6 months, 45.3% girls). The Spearman–Brown formula was applied to determine the minimum reporting time needed to achieve a reliability coefficient of 0.70 for time spent in PA, SB and sleep, and 24-h movement behavior compositions. General linear mixed-effects models were used to test our hypothesis that accelerometer-derived acceleration would be lowest during app-based estimates of sleep, followed by SB, and highest during PA. Additionally, we tested 55 sub-hypotheses to examine expected differences and similarities in accelerometer-derived acceleration across app-based activity categories. Results The minimum required reporting time was at least 2 days of 20 h for sleep, 2 days of 23 h for PA, 4 days of 17 h for SB, and 2 days of 23 h for the composition of 24-h movement behaviors. As hypothesized, lowest accelerations were recorded during sleep and highest accelerations during PA. We found consistent support for 21 out of 55 sub-hypotheses, with significantly higher acceleration for active play and active transport than for sedentary activities, except for passive transport. Conclusions To reliably assess the composition of 24-h movement behaviors in 0–4-year-olds, activities need to be reported in the MLM app for at least two full days. The MLM app shows promise for assessing 24-h movement behaviors, although some specific activities require further investigation.