24-hour movement behaviors and internalizing and externalizing problems among Japanese preschool children: A...

Because 24-h movement behaviors share a finite time budget, treating them as independent exposures may obscure their joint associations with mental health. This study examined associations of the 24-h movement behavior composition with internalizing and externalizing problem scores among Japanese preschool children using compositional data analysis (CoDA) and compositional isotemporal substitution.

A total of 469 Japanese preschool children aged 3-5 years wore a triaxial accelerometer (Active Style Pro HJA-750C) to assess sedentary behavior (SB), light physical activity (LPA), and moderate-to-vigorous physical activity (MVPA). Nighttime sleep duration and Strengths and Difficulties Questionnaire outcomes were assessed by parent report. Isometric log-ratio regression and compositional isotemporal substitution models were adjusted for age, sex, and continuous body mass index.

A greater relative allocation to MVPA, compared with the geometric mean of sleep, SB, and LPA, was associated with a lower internalizing problem score (unstandardized B = -1.25, 95% confidence interval, -2.40 to -0.10; p = 0.03). No first-pivot estimate was statistically significant for externalizing problem scores. In model-based 15-min/day reallocation scenarios, reallocating time from SB to MVPA corresponded to a 0.27-point lower predicted internalizing score, whereas the reverse reallocation corresponded to a 0.36-point higher score. Similar inverse associations were observed in the full-sample waking-time composition and residual-adjusted models, but not in the residual-restricted samples.

These cross-sectional findings indicate that a greater relative allocation of time to MVPA was associated with lower internalizing problem scores, but they do not establish a protective or causal effect.