Background & objectives: Sleep plays an important role in development of children. Sleep affects physical growth, behavior, emotion and cognitive function. Also, learning activities and attention are affected by sleep quality. This study aimed to determine the sleep disorders and related factors among preschool children in the health centers affiliated to Shahid Beheshti University of Medical Sciences, Tehran, Iran, 2013.

Methods: This was a descriptive-cross sectional study carried on 400 children selected by cluster sampling method. At first, health centers divided to zones of North, South, West and East then two centers from each zone were selected. Data were collected by Questionnaire included two sections of demographic characteristics and the Children&rsquos Sleep Habit Questionnaire (CSHQ). Additionally factors including age, BMI, being unwanted or wanted child, job and education of parents were included. Data were analyzed by SPSS v.16 and descriptive statistics and Chi-square test was used. P-values under 0.05 were considered statistically significant.

Results: Mean age of children was 64.3�9.3 months. Prevalence of sleep disorders was 36.3%. Sleep disorders were associated with age, body mass index of children, mother&rsquos diseases, father&rsquos drug abuse and marital status of parents (p<0.05).

Conclusion: Sleep disturbances threaten growth and development of children, and should be considered as important and effective agent in their health. Nutritional problems leading to obesity, high risk behaviors of parents, disease of mother and marital conflict of parents may lead to sleep disorders in children. We suggest parents must be diligent in making safe and conflictless environment