MATERIALS AND METHODS
This descriptive cross-sectional study, conducted between November 2013 and January 2014, included all children with DS attending institutions for individuals with special needs in Sana’a, Yemen. At the time this study was carried out, there were 115 children with DS attending three schools for mentally disabled individuals. The inclusion criteria implemented were: (1) cytogenetic diagnosis of trisomy 21, (2) adequate cooperation from the children, and (3) informed consent from the children's legal representatives. The exclusion criteria were detrimental systemic diseases, compound disability, and extremely uncooperative children. The total eligible sample comprised 101 DS children aged between 6 and 16 years.