Periodic Reporting for period 1 - DLD-PI (Developmental Language Disorder - Prevention and Intervention)
Reporting period: 2021-01-01 to 2022-12-31
Language is the foundation for individual and societal well-being. Although many children learn language effortlessly, two out of 30 students in a classroom struggle with language development without a known biomedical cause. This condition is known as developmental language disorder (DLD). DLD affects 5.8 million children across Europe and has long-term detrimental effects on academic performance, social-emotional well-being, and employment opportunities for those affected. In addition to the individuals with DLD, their families and society are burdened by these challenges, which are unfairly distributed as many of those with DLD come from disadvantaged backgrounds. This raises public health concerns and hence invokes public health/preventative intervention models. Despite the public health concerns and long-term adverse consequences associated with DLD, it remains an unstudied and relatively unknown disorder. It is urgent that we develop more sensitive diagnostic tools and preventative interventions for individuals with DLD. By using the Finnish Birth Cohorts 1987 and 1997, DLD-Prevention and Intervention (DLD-PI) aims to identify important risk and protective factors for DLD, develop a risk prediction algorithm for identifying preschoolers at risk of DLD, and determine significant risk and protective factors associated with life outcomes. DLD-PI serves the key objectives of Horizon 2020: excellent science and tackling societal challenges. DLD-PI aims to have a wide impact as they enable better prediction of individual trajectories and outcomes of DLD. In addition to raising public awareness of DLD, this proposal is expected to maximize efficiency in targeting and timing preventative interventions for DLD, affecting multiple stakeholders (clinicians, educators, and the public).
The researcher and the research team investigated the prevalence of DLD and analyzed its comorbid conditions and diagnostic changes over time, using the Finnish Birth Cohorts 1987 and 1997. The results indicate that the prevalence of diagnosed DLD identified (0.29% in FBC1987; 1.10% in FBC1997) was similar to previous findings in Finland (see Kunnari et al., 2019 for a review), but lower than those in Australia (Law et al., 2017), the UK (Norbury et al., 2016), and the US (Tomblin et al., 1997) obtained through population screening. Children with DLD were at significantly increased risk of comorbid mood, behavioral and emotional and academic related disorders. Notably children with DLD were more than 16 times more likely to have developmental disorders (including academic related disorders) than their non-DLD peers. Over the course of their lives, 57.71% of individuals with DLD had one or more comorbid conditions, while 42.29% only had DLD; the conditions that tended to be diagnosed within the same age band as DLD were other speech-language disorders, motor coordination disorders, multiple developmental disorders, and behavioral and emotional disorders; and the conditions that tended to be diagnosed at a later age band than DLD were academic-related disorders and psychiatric disorders (i.e. mood disorders and neurotic disorders). The results were presented at the 12th Society for Longitudinal and Life Course Studies in October 2022 and the American Speech-Language-Hearing Association, USA in November 2022. An overview of the risk and protective factors for DLD was published in a book chapter (Laasonen & Park, 2022).
The DLD-PI project addresses important issues related to societal and research needs regarding DLD at the regional and global levels. The project results indicated that only a small percentage (0.3-1.1%) of children with DLD received a formal diagnosis in Finland. DLD is still diagnosed using ICD-10, which includes stringent diagnostic criteria, in Finland. This may explain the difference in the prevalence of DLD between Finland and other countries, such as the United Kingdom, the United States, and Australia. The study raises awareness of the fact that the prevalence of DLD varies significantly based on the diagnostic criteria used across countries. The difference in how DLD is identified is likely to result in different risk and protective factors, as well as comorbidities and consequences across countries. Furthermore, the study indicates that it is necessary to investigate whether children with low language who are not diagnosed with DLD receive adequate support, as well as whether a change to more inclusive DLD criteria, as advocated by Bishop et al. (2017), would lead to a greater level of access to support for children with low language. Although patterns of comorbidity are complex and change over time, it is very clear that both academic and mental health outcomes must be considered when designing interventions and systems to support children with DLD.