# Sleep Hours, Wake-Up Time, Bedtime, Breakfast Skipping, and Japanese-Style Diet (Staple Food, Main Dish, and Side Dish): A Cross-Sectional Study of Schoolchildren in Saga Prefecture

## TL;DR

This study shows that schoolchildren in Japan who sleep and wake up early are less likely to skip breakfast and more likely to eat balanced meals.

## Contribution

The study identifies specific sleep and wake-up time associations with breakfast skipping and traditional Japanese meal patterns in children.

## Key findings

- Children sleeping ≥9 hours had parents in their 30s with healthy diets.
- Waking up before 6:30 reduced breakfast skipping, while waking after 7:00 increased it.
- Earlier bedtimes were linked to fewer breakfast skips and more balanced meals.

## Abstract

Objectives: We investigated the association between children’s waking time and bedtime and contents of home meals, focusing on ‘skipping breakfast’ and ‘meal of staple food, main dish, and side dish’ (SMS meal). Methods: A cross-sectional survey concerning children’s lifestyle habits and dietary habits was conducted at seven primary schools within Saga Prefecture in northern Kyushu, Japan, with 2457 parents/guardians participating. Logistic regression analyses were used to estimate odds ratios (ORs) and 95% confidence intervals (CIs) for the association of sleep hours, wake-up time, and bedtime, with breakfast skipping and having SMS meals. Results: Elementary schoolchildren sleeping for ≥9 hours were more likely to have parents/guardians in their 30s, who were full-time parents and maintained a healthy diet. Wake-up times and bedtimes were significantly associated with breakfast skipping frequency. Compared to the wake-up time from 6:30 to 6:59, ORs for the frequency of skipping breakfast was 0.52 (95% CI: 0.36–0.74, p < 0.001), for those waking before 6:29 and 2.23 (95% CI: 1.64–3.04; p < 0.001) for those waking after 7:00.Frequency of skipping breakfast decreased with earlier bedtimes. Compared to bedtimes from 21:00 to 21:59, ORs for having SMS meals were 0.64 for those with bedtimes before 21:00 (95% CI: 0.25–1.64) and 2.35 for those with bedtimes after 22:00 (95% CI: 1.77–3.11, p < 0.001). Compared to wake-up times from 6:30 to 6:59, waking up both before 6:29 (OR = 0.77, 95% CI: 0.63–0.94, p < 0.01) and at 7:00 or after (OR = 1.30, 95% CI: 1.00–1.69, p = 0.05) were associated with breakfast and dinner with SMS meals. A statistical interaction existed between wake-up time/bedtime and breakfast skipping. Compared to those waking before 6:30 and sleeping before 22:00, waking after 7:00 and sleeping after 22:00 was associated with skipping breakfast (OR = 2.11, 95% CI: 1.48–3.01; p for interaction = 0.04). Thus, children should sleep before 22:00 and wake up before 7:00 to prevent breakfast skipping and ensure a well-balanced diet with SMS meals. The ‘Early to Bed, Early to Rise, and Don’t Forget Your Breakfast’ initiative significantly improved elementary schoolchildren’s eating habits. Conclusions: Sleep hours, bedtime, and wake-up times are important factors affecting Japanese schoolchildren’s dietary habits, specifically in terms of breakfast skipping and having SMS meals.