Validity and reliability of the Japanese version of the Movement Behaviour Questionnaire-Child (MBQ-C) for assessing active play, screen time, and sleep in preschool children

Background: Valid and feasible measures of preschoolers' 24-hour movement behaviours are needed for population-level research. We developed a Japanese version of the Movement Behaviour Questionnaire-Child (MBQ-C) and evaluated its measurement properties and practicality. Methods: After translation and cross-cultural adaptation following the COSMIN procedure, including cognitive interviews, we evaluated the questionnaire in a cross-sectional validation study of Japanese children aged 3-6 years. Concurrent validity was assessed against hip-worn accelerometry and a 7-day diary; we also examined test-retest reliability, measurement error, agreement between response formats and modes, and practicality (completion time, burden, and clarity). Analyses used Spearman correlations, intraclass correlation coefficients, the SEM, smallest detectable change (SDC), and Wilcoxon signed-rank tests. Results: Of 208 children, 170 provided valid accelerometer and diary data for the concurrent-validity analysis, and 187 completed the MBQ-C for the questionnaire-based analyses. Concurrent validity was weak for active and energetic play (Spearman {rho} = 0.12-0.26), strong for total screen time (0.78-0.85), and moderate for total sleep (0.48-0.58). Test-retest reliability was moderate to good (ICC, 0.66-0.81), and within-child variability was lowest for sleep (CV 3%) and highest for the physical activity items (21-33%). The open- and closed-ended versions showed no significant differences; paper-electronic agreement was good for screen time and sleep but poor for active play. Completion took approximately 6-9 minutes, with low reported burden. Findings were robust in sensitivity analyses. At the group level, SDC for a mean was SDCind/{surd}N: 119.8/{surd}N, 74.0/{surd}N, 112.6/{surd}N, and 92.5/{surd}N min/day for active play, energetic play, total screen time, and total sleep, respectively (N = number of children surveyed). The systematic differences between the two test-retest occasions were +15.7, +6.5, +4.0, and -5.4 min/day, respectively. Conclusions: The Japanese MBQ-C is a practical option for assessing preschoolers' active play, screen time, and sleep at the group level. By quantifying its group-level measurement error, this study provides benchmarks for interpreting group-level differences and change, supporting the use of the MBQ-C in surveillance and evaluation of programmes delivered at scale.