This study investigated the relationship between sleep habits in early childhood and academic performance and non-cognitive skills in the first grade. We retrospectively analyzed a longitudinal population-based cohort from birth through early childhood, up to elementary school, in Amagasaki City, Japan. The primary outcome was academic performance in the first grade. Other outcomes were self-reported non-cognitive skills. Overall, 4395 children were enrolled. Mean national language scores for children with bedtimes at 18:00-20:00, 21:00, 22:00, and ≥ 23:00 were 71.2 ± 19.7, 69.3 ± 19.4, 68.3 ± 20.1, and 62.5 ± 21.3, respectively. Multiple regression analysis identified bedtime at 3 years as a significant factor associated with academic performance. However, sleep duration was not significantly associated with academic performance. Bedtime at 3 years also affected non-cognitive skills in the first grade. Diligence decreased with a later bedtime (21:00 vs. 18:00-20:00; odds ratio [OR]: 1.98, 95% confidence interval [CI] 1.27-3.09; 22:00 vs. 18:00-20:00; OR: 2.15, 95% CI 1.37-3.38; ≥ 23:00 vs. 18:00-20:00; OR: 2.33, 95% CI 1.29-4.20). Thus, early bedtime at 3 years may be associated with a higher academic performance and better non-cognitive skills in the first grade. Optimum early-childhood sleep habits may positively impact academic future.
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