Visually detected non-rapid eye movement stage 2 sleep spindle density at age five years predicted prosocial behavior positively and hyperactivity scores negatively at age nine years

A higher density of sleep electroencephalogram (EEG) spindles has been cross-sectionally associated with more efficient cortical-subcortical connectivity, superior intellectual and learning abilities, and healthier emotional and behavioral traits. In the present study, we explored to what extent sleep spindle density (SSD) at age five years could predict emotional and behavioral traits at six and nine years.; A total of 19 healthy preschoolers at age five years underwent in-home sleep EEG recordings for visual scoring of non-rapid eye movement stage 2 (NREM-S2) sleep spindles, and SSD in NREM-S2 was calculated. Parents and teachers rated children's emotional and behavioral characteristics at ages five, six, and nine years.; Higher SSD at five years predicted higher prosocial behavior scores at nine years, as rated by parents and teachers, and lower hyperactivity scores as rated by teachers. Multiple regression analyses showed that SSD predicted prosocial behavior and hyperactivity independently of earlier prosocial behavior or hyperactivity.; The pattern of results suggests that a higher SSD at five years is predictive of higher scores for positive emotional and behavioral characteristics four years later. Therefore, spindle density indices might be acknowledged as an indicator not only of cognitive but also of emotional-behavioral development in children.