Lifestyle behaviors from early childhood to junior high school in rural Japan: a cross-sectional study

BACKGROUND: Understanding combinations of lifestyle behaviors, including screen time, outdoor activity, and sleep, is essential for promoting children's health. However, evidence spanning multiple developmental stages within the same community remains limited, particularly in rural areas of Japan. METHODS: This cross-sectional study examined school stage and sex differences in lifestyle behaviors among children living in a rural region of southern Japan. Participants included 1,192 children from early childhood through junior high school (49.8% girls, 50.2% boys), recruited from a total of 10 schools (four preschools, four elementary schools, and two junior high schools) in the study areas. In Japan, preschool includes children aged 1-5 years, elementary school includes Grades 1-6 (ages 6-12), followed by junior high school (Grades 7-9; ages 12-15) and high school (Grades 10-12; ages 15-18). Information on sleep timing, sleep duration, outdoor activity time, and screen time was collected using parent- and self-reported questionnaires. Differences by school stage and sex were analyzed using two-way analysis of variance and chi-square tests, with linear regression models used to examine trends across ordered developmental stages. RESULTS: Across all school stages, average sleep duration fell below age-specific recommendations, decreasing from 9.60 h/day in toddlers to 7.83 h/day in junior high students. This decline was driven by progressively later bedtimes (21:02 to 22:42) rather than changes in wake times. Screen time exhibited a nearly fourfold increase across stages, rising from 1.46 to 5.70 h/day (p < 0.001), suggesting early consolidation of screen-related behaviors. Outdoor play time was 0.28 h/day in toddlers, 0.38 h/day in preschoolers, 0.55 h/day in both lower and upper elementary school children, and 0.85 h/day in junior high school students. CONCLUSIONS: Unhealthy lifestyle behaviors related to sleep, physical activity, and screen use were observed across multiple developmental stages within a single rural community. These patterns appear to emerge early in childhood and intensify with age, underscoring the importance of a life-course approach and the need for early, developmentally appropriate public health strategies to support healthier daily routines among children in rural regions.