Balancing Nighttime Sleep and Midday Naps: The Role of a Biphasic Sleep in Chinese Adolescents’ Academic Performance and Health

This study examined how daily sleep allocation—nighttime sleep and midday nap duration—influences adolescents’ academic performance and physical health, with a focus on gender differences. A school-based survey was conducted among Chinese adolescents aged 13–15 years (N = 27236). Sleep habits were assessed via caregiver-reported questionnaires. Academic and physical outcomes were assessed using core-subject scores and fitness evaluations. Three-way ANCOVAs revealed a curvilinear association between nighttime sleep and both outcomes, peaking at 8–9 h. Midday napping was associated with better academic achievement and health, but its benefits were modulated by total daily sleep and gender. Girls exhibited greater resilience to nighttime sleep restriction (<8 h) and benefited more from longer naps (>30 min), whereas boys need adequate nighttime sleep and benefited from short-to-moderate naps (15–60 min). These findings highlight the importance of a balanced biphasic sleep pattern—8 to 9 h of nighttime sleep plus a 30–60 min nap, offering practical implications for adolescent sleep guidelines and school scheduling policies.