Prevalence, co-occurring difficulties, and risk factors of developmental language disorder: first evidence for Mandarin-speaking children in a population-based study.

Background: Developmental language disorder (DLD) is a condition that significantly affects children's achievement but has been understudied. We aim to estimate the prevalence of DLD in Shanghai, compare the co-occurrence of difficulties between children with DLD and those with typical development (TD), and investigate the early risk factors for DLD.

Methods: We estimated DLD prevalence using data from a population-based survey with a cluster random sampling design in Shanghai, China. A subsample of children (aged 5-6 years) received an onsite evaluation, and each child was categorized as TD or DLD. The proportions of children with socio-emotional behavior (SEB) difficulties, low non-verbal IQ (NVIQ), and poor school readiness were calculated among children with TD and DLD. We used multiple imputation to address the missing values of risk factors. Univariate and multivariate regression models adjusted with sampling weights were used to estimate the correlation of each risk factor with DLD.

Findings: Of 1082 children who were approached for the onsite evaluation, 974 (90.0%) completed the language ability assessments, of whom 74 met the criteria for DLD, resulting in a prevalence of 8.5% (95% CI 6.3-11.5) when adjusted with sampling weights. Compared with TD children, children with DLD had higher rates of concurrent difficulties, including SEB (total difficulties score at-risk: 156 [17.3%] of 900 TD vs. 28 [37.8%] of 74 DLD,  < 0.0001), low NVIQ (3 [0.3%] of 900 TD vs. 8 [10.8%] of 74 DLD,  < 0.0001), and poor school readiness (71 [7.9%] of 900 TD vs. 13 [17.6%] of 74 DLD,  = 0.0040). After accounting for all other risk factors, a higher risk of DLD was associated with a lack of parent-child interaction diversity (adjusted odds ratio [aOR] = 3.08, 95% CI = 1.29-7.37;  = 0.012) and lower kindergarten levels (compared to demonstration and first level: third level (aOR = 6.15, 95% CI = 1.92-19.63;  = 0.0020)).

Interpretation: The prevalence of DLD and its co-occurrence with other difficulties suggest the need for further attention. Family and kindergarten factors were found to contribute to DLD, suggesting that multi-sector coordinated efforts are needed to better identify and serve DLD populations at home, in schools, and in clinical settings.

Funding: The study was supported by Shanghai Municipal Education Commission (No. 2022you1-2, D1502), the Innovative Research Team of High-level Local Universities in Shanghai (No. SHSMU-ZDCX20211900), Shanghai Municipal Health Commission (No.GWV-10.1-XK07), and the National Key Research and Development Program of China (No. 2022YFC2705201).