Introduction (Clinical disorder)
Developmental dyslexia (DD) is a special impairment that is characterized by persistent and severe problems in learning skills (Yang et al.,2022). These particular problems do not occur because of inadequate schooling, or acuity problems associated with visual and mental age. Developmental dyslexia is also known as a specific reading disorder or specific reading disability (Yang et al., 2022). Many children with this disorder mainly experience negative attitudes and positive well-being, which is low, and have higher anxiety when reading. After the children start going to primary school, that is the time they are taught how to read, and by the time they finish primary school, their word-reading skills are comparable to the skills of adults (Yang et al., 2022). As the child begins attending structured schooling, the diagnosis of this disorder or disability is achieved. Primary school is an essential point in identifying early interventions, and screening is done to address risk factors and identify the possible reading challenges the child is experiencing (Yang et al., 2022).According to, Diagnostic and Statistical Manual for Mental Disorders, Fifth Edition (DSM-5), difficulties in mathematical reasoning, arithmetic, and reading skills during formal years of schooling are several symptoms that are associated with early diagnosis of a learning disorder (Weis,2020).
Summary of a recent meta-analysis
Yang et al. (2022) conducted a meta-analysis and systematic analysis according to PRISMA (preferred reporting items for systematic reviews and meta-analyses) in order to review the studies done before that reported a higher prevalence of dyslexia in children who are in primary school. However, their study also aimed at addressing two other key issues: (a) whether DD prevalence varies according to variables such as writing systems and gender, (b) the global prevalence of childhood DD. They reviewed studies that have done from the 1950s to June 2021 (M.Z and X.L) are the two researchers who conducted the literature review independently of EMBASE, SpringerLink, Cochrane, the OATD database, Web of Science, PubMed, ProQuest, EBSCO, knowledge database of the China Hospital, CQ-VIP, Wanfang, and China National Knowledge Infrastructure. These two researchers used search terms that are related to developmental DD (learning disability or reading disorder, reading disability or dyslexia) and prevalence (epidemiology, incidence rate, detectable rate, and prevalence). The study design included participants (children) of primary school from grades one to six of age between six to 13(6-13 years). This study included the prevalence of DD as the secondary or main outcome, the children were recruited in the study through a sampling method, and symptoms of DD were assessed by the use of good psychometrics.
This meta-analysis excluded the following studies; gray literature published by commercial or industrial entities, organizations, and government for abstracts, proceedings, conferences, academic purposes, editorials, review articles, randomized clinical trials, and case-control studies. M.Z. and X.L examined the abstracts and titles of all the records retrieved from the literature search independently. The collected data included the following information; prevalence estimate, the number of participants (children) who have been screened as DD, sample size, diagnostic criteria, diagnostic materials, sampling strategy, study design, country, year of publication, first author, and title.
Summary of key findings
The initial literature search identified 6564 records in total, as illustrated in Figure 1 (shown on the last page). The last set that consisted of 56 articles, with about 58 studies, was involved in the quantitative synthesis after the eligibility criteria were applied. 41 studies of the 58 studies, approximately 70.69% reported data related to prevalence for both girls and boys.31 studies of 58 studies (53.45%) were carried out among participants (children ) utilizing alphabetic scripts. The most used method was random sampling, and the most studied grade was grade three (21,36.21%). Therefore, this meta-analysis and systematic review estimated the prevalence of dyslexia among children in primary schools worldwide, with a prevalence of approximately 7.10%. However, the ratio of girls to boys was about 1:2, and this implied that there were differences in gender. Also, the results reported that boys have a higher prevalence of DD than girls. Another significant finding of the study is that prevalence of DD does not vary according to the writing system ( logo-graphic scripts and alphabetical scripts). Furthermore, there were no differences associated with language-specific. The prevalence was only influenced by the sample size and operational definition.
Quality of meta-analysis
The authors used PRISMA statements for reporting and design, and the study’s protocol was registered in PROSPERO, the registration number of this study is CRD42021232958. Their exclusion and inclusion criteria were clear, and their search strategy was reproducible. The criteria of study inclusion were that : participants were mainly children of primary school from grades one to six of age between six to 13(6-13 years), this study also included the prevalence of DD as the secondary or main outcome, the children were recruited in the study through a sampling method, and symptoms of DD were assessed by the use of good psychometrics. The criteria of study exclusion were that: articles contained inadequate information about the information regarding sample, the study did not involve other students apart from those in primary schools and the articles were not accessible in full-text form via library requests or through online database.The authors rated the quality of the articles included in the study based on the STROBE (Strengthening the Reporting of Observational Studies in Epidemiology) in the following dimensions: analytical methods, outcomes assessment, participation rate, sample size, and sample population.
Relevance of this meta-analysis
This study is appropriate because it is the first meta-analysis study that has estimated the prevalence of DD among primary school children. Additionally, the results of this study suggested that developmental dyslexia is a major public health disorder that affects many children worldwide, especially those in grades one to six. Also, this meta-analysis provides insight into a component that would be important for clinical psychologists to consider during treatment, early prevention, and assessment of this disorder. Furthermore, the study provides comprehensive evidence that confirms high prevalence of dyslexia in children which is well-known variable. It also makes clear that boys are more likely than girls to have dyslexia, which clinical psychologists should keep in mind while conducting assessments and developing early preventive strategies.
The analysis also provides explanation of environmental and biological factors that causes these dyslexia such as perinatal complications, immunological factors, genetic causes and differences that are associated with brain functioning due to sensitivity to androgens or differential exposure. Clinical psychologists should include these findings when evaluating dyslexic children since they can assist them spot those who are more at risk of the disease. Moreover, these risk factors can be the focus of early prevention efforts, which may lower the prevalence of dyslexia in the general population. The meta-analysis emphasizes the value of early identification and intervention for dyslexic children when it comes to treatment. The study discovered that early intervention programs, including phonological training and reading instruction, were successful in enhancing the reading abilities of all the primary children who experience dyslexia. The importance of early identification and intervention to improve outcomes makes this knowledge essential for clinical psychologists who work with children who have dyslexia.
Yang, L., Li, C., Li, X., Zhai, M., An, Q., Zhang, Y., … & Weng, X. (2022). Prevalence of developmental dyslexia in primary school children: a systematic review and meta-analysis. Brain Sciences, 12(2), 240. https://www.mdpi.com/1491808
Weis, R. (2020). Introduction to abnormal child and adolescent psychology. Sage publications. https://edge.sagepub.com/weis3e/instructor-resources
Figure one: This is a PRISMA flow diagram of study selection and literature search