BackgroundInadequate sleep in children relates to medical and psychosocial problems. However, not much is known about the effects of sleep problems persisting from pre‐school to school age on somatic and psychosocial symptoms.ObjectivesTo examine the associations between sleep disturbances and psychosocial symptoms, somatic complaints, medical problems at school age.MethodsThis was a population‐based 4‐year follow‐up study of sleep problems in Finnish children (n = 470). Parents filled in Sleep Disturbance Scale for Children during pre‐school and school years. Children were categorized into four groups: no sleep problems, sleep problems only at pre‐school or only at school age, and persistent sleep problems. At follow‐up the parents filled in Child Behavior Checklist and a background questionnaire.ResultsThe children with persistent sleep problems (9%) had a 16‐fold risk of having psychosocial symptoms on subclinical/clinical range compared with the children without sleep problems. The psychosocial symptoms that were related strongest to prolonged sleep problems were aggression, social and attention problems, and anxious/depressed mood. Also, somatic complaints (ninefold risk) and medical problems (P < 0.001) were typical for children with persistent sleep problems.ConclusionsPersistent sleep problems in children associate with high levels of psychosocial, somatic and medical problems. In paediatric health care more attention should be paid to recognizing, monitoring of the persistence and treatment of sleep problems before school transition period.