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Autism spectrum disorder among 16- to 30-month-old children in Bangladesh: Observational cross-sectional study.

LAY ABSTRACT
A nationwide survey was done in Bangladesh to assess autism spectrum disorder prevalence in 16- to 30-month-old children at urban-rural distribution and to determine the association with socioeconomic and demographic conditions. A three-stage cluster sampling method was used where districts from all divisions were selected in the first stage, census enumeration areas as blocks of households were selected in the second stage and households (within the blocks) were selected in the third stage. Thereby, it included 38,440 children from 37,982 households (71% rural, 29% urban) aged 16-30 months from 30 districts of eight divisions of Bangladesh. Screening was done with a 'Red Flag' tool and Modified Checklist for Toddlers and a final diagnosis using Diagnostic and Statistical Manual of Mental Disorders, 5th Edition for autism spectrum disorder. Autism spectrum disorder prevalence was 17 per 10,000 young children - in other words, one in 589 young children. Boys were found at higher risk of autism (one in 423 boys; one in 1026 girls). Prevalence of autism spectrum disorder was higher in urban environments than in rural ones - 25/10,000 and 14/10,000, respectively. More autism spectrum disorder children were found in advanced age groups of parents, especially mothers, and in households with a higher wealth quintile. This survey is significant as it covers both urban and rural areas and specifically targets very young children. The involvement of the Bangladesh Bureau of Statistics, as well as support from the entire healthcare system infrastructure, makes this survey more representative on a national level. Its results will form a database to support the development of an effective early intervention programme in Bangladesh. We hope it will prove useful for researchers, clinicians and frontline healthcare workers, and inform the decisions of policymakers and funders in Bangladesh.