Prevalence of Developmental Language Delay in Children Aged 3 to 6: Population-based Study

Objectives: This study aimed to investigate the prevalence of developmental language delay in preschool children aged 3 to 6 years, considering gender, region, and cognitive level. Methods: A total of 5,099 children, representing 15.4% of all children aged 3 to 6 years in Gangwon Special Self-Governing Province, participated in the study. A screening assessment was conducted using the language domain of the K-DST (Korean Developmental Screening Test for infant & children) with children below -1 SD on the screening were referred for in-depth language assessment using the PRES (Preschool Receptive-Expressive Language Scale) and the REVT (Receptive & Expressive Vocabulary Test). Among the children who participated in the screening test, 1,246 (22.5%) were referred for the indepth assessment, and 925 (80.7%) of them completed the in-depth assessment. Prevalence was calculated as the proportion of children with DLD (Developmental Language Delay) out of the total participants (5,099 children) and was analyzed by type of delay, age, region, and cognitive level. Results: 10.4% of children were diagnosed with DLD. The prevalence of combined receptive and expressive language delay (7.5%) was higher than that of expressive language delay only (2.9%). When the sample was limited to children with cognitive scores above -1 SD, the prevalence was 2.6%, and 6.0% when limited to scores above -2 SD. Prevalence decreased with age. Boys had a higher prevalence than girls, and children living in small cities or rural areas had a higher prevalence than those in mid-sized cities. Conclusion: This study is significant as it is the first population-based prevalence study conducted in Korea through a systematic procedure. The results of this study are expected to contribute to understanding the prevalence of language delay in young children and to serve as useful data for the development of services and policies for these children.