Area socioeconomic deprivation and language delay in children in population data in Germany

Abstract Background Language delay (LD) in children is a public health concern as it can contribute to mental health problems and long-term health impairments. Studies have shown that socioeconomic factors on an individual level (family socioeconomic position; SEP) and an area level (area deprivation) are both associated with LD. However, there is a lack of knowledge if individual SEP and area deprivation interact in their effect on LD. This study explores whether individual SEP modifies the association between area deprivation and LD. Methods Unselected, cross-sectional data of children aged under 6 to 7 years from the ‘School Entry Survey’ 2021 in the German federal state of Brandenburg (n = 24,788) were linked to the ‘German Index of Socioeconomic Deprivation’ (GISD; area deprivation) on the level of school municipalities. Using binary multilevel models [odds ratio (OR), 95% confidence interval], LD [no | yes: 19.3%] was regressed on area deprivation [GISD; metric] and individual SEP [low | medium | high], along with an interaction term between both. The model was repeated stratified by individual SEP. Sensitivity analyses included sex stratification [female | male]. Results The interaction between GISD and individual SEP was associated with LD (ORmediumSEP*GISD=1.13, 1.04-1.24; ORlowSEP*GISD=1.27, 1.13-1.43), with the main effect of GISD (OR = 0.85, 0.77-0.93). With SEP stratification, GISD was only partially associated with LD (ORhighSEP = 0.81, 0.73-0.91; ORmediumSEP=0.97, 0.89-1.07; ORlowSEP=1.14, 0.99-1.32). Results were comparable for both sexes. Conclusions Both individual SEP and area deprivation contribute interactively to LD. Future research on area-level factors and childhood health should stratify analyses by individual SEP, as area-level effects may be contradictory depending on individual SEP. From a life course perspective, public health should address inequalities in LD to reduce health inequalities. Key messages • Area-level socioeconomic deprivation is associated with language delay in early childhood, with associations varying by individual-level family socioeconomic position. • Area-level health research in childhood should stratify design and analysis of studies according to individual-level family socioeconomic position.