In pre-school children, sleep objectively assessed via sleep-EEGs remains stable over 12 months and is related to psychological functioning, but not to cortisol secretion

Cross-sectional studies provide evidence that in pre-schoolers poor sleep is by this age already associated with both poor psychological functioning and an increased cortisol secretion. However, long-term studies on the stability of sleep in pre-schoolers are scarce. The aim of the present study was therefore to investigate objectively assessed sleep in pre-schoolers longitudinally, and to predict sleep, psychological functioning and cortisol secretion prospectively as a function of sleep 12 months earlier.; A total of 58 pre-schoolers (mean age: 5.43 years; 47% females) were re-assessed 12 months later (mean age: 6.4 years). Sleep-EEG recordings were performed, saliva cortisol was analysed, and parents and experts rated children's psychological functioning.; Longitudinally, poor objective sleep at age 5.4 years was associated with poor objective sleep and psychological difficulties but not cortisol secretion 12 months later. At age 6.4 years, poor sleep was concurrently associated with greater psychological difficulties and increased cortisol secretion.; In pre-schoolers, poor sleep objectively assessed at the age of 5.4 years was associated with poor sleep and psychological difficulties one year later. Data indicate that in pre-schoolers, sleep remains stable over a 12-months-period. Pre-schoolers with poor sleep appear to be at risk for developing further psychological difficulties.