Prevalence estimates of neurodevelopmental disorders in Japan: A community sample questionnaire study.

AIM: Prevalence estimates of neurodevelopmental disorders have been calculated by questionnaire surveys scored by a single rater, which introduces inherent rater biases. The present study aimed to estimate the prevalence and comorbidity rates of four neurodevelopmental disorders based on both parent and teacher rating scales. METHODS: We performed a community sample survey recruiting 3852 children aged 6 to 9 years. Parents and teachers evaluated clinical conditions in children using questionnaire-style scales. These scales with cut-off values were used to estimate the prevalence and comorbidity rates of attention deficit hyperactive disorder, autism spectrum disorder, specific learning disorder (or developmental dyslexia), and developmental coordination disorder. RESULTS: The prevalence estimates were separately confirmed according to the raters. Some estimates were higher than those in previous studies conducted in other countries. We also found a large disagreement between the parent and teacher rating scores. Moreover, the degree of agreement between two raters varied depending on the severity of the child's clinical condition. CONCLUSION: These estimates are the first findings based on evaluating children by two different raters. The prevalence and comorbidity estimates are informative for researchers and clinicians of pediatric neurology. The disagreements between two different raters raise questions about previous estimates of neurodevelopmental disorders.

Is the motor skills checklist appropriate for assessing children in Japan?

PURPOSE: Motor skill screening tools are essential for the early detection of developmental coordination disorder (DCD). The present study aimed to examine any cultural and rater effects on these tools. This then enabled us to judge the validity of the original cut-off values for identifying diagnosable children. METHODS: A community sample survey was performed in Japan; 3852 children aged 6-9 years were recruited. Both parents and teachers evaluated the motor skills of their children using the Movement Assessment Battery for Children - Second Edition Checklist. The psychometric properties were evaluated and the scoring characteristics examined based on the type of rater and country of origin, as compared to data originally sampled in the UK. RESULTS: High reliability and validity of the Japanese samples were confirmed. The Japanese adults evaluated their children's motor skills more rigorously than the Europeans. Additionally, there was a large disagreement between parent and teacher rating scores; the degree of agreement varied depending on the severity of motor deficits in the child. CONCLUSION: The first findings from a Japanese sample suggest that the assessment of motor skills in children is significantly affected by culture and rater. These cultural characteristics and rater biases strongly suggest that new cut-off values, reflecting country and rater type, be introduced for identifying children at risk of DCD.