Visually detected NREM-S2 sleep spindle-density at age five predicted prosocial behavior positively and hyperactivity scores negatively at age nine

Cross-sectionally, a higher density of sleep-electroencephalogram (EEG) spindles has been 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 could predict emotional and behavioral traits at six and nine years. Methods: Nineteen healthy preschoolers at age five 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 three time points, at five, six and nine years. Results: 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 Conclusions: 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. Accordingly, spindle density indices might be acknowledged not only as an indicator of cognitive but also of emotional-behavioral development in children.