Prevalence of autism spectrum disorders among children in China: a systematic review

BACKGROUND: There are no reliable estimates of the prevalences of autism and autism spectrum disorders (ASD) in China. OBJECTIVE: Combine results across studies to estimate the prevalences of autism and ASD among Chinese children under the age of 18, and assess variations in the prevalences with respect to gender, ethnicity, and urban versus rural residence. METHODS: Based on pre-defined inclusion and exclusion criteria, studies were identified by searching the following databases: Chinese National Knowledge Infrastructure, Chongqing VIP database for Chinese Technical Periodicals, WANFANG DATA, Chinese Biological Medical Literature Database, Pubmed, and Web of Science. Statistical analysis was conducted using R-2.15.2 software. RESULTS: The 24 studies meeting inclusion criteria included 5 registry studies from Taiwan and Hong Kong (covering a total of 14570 369 children) and 19 community-based screening and diagnostic studies from mainland China (with a combined sample of 771 413 children). The annually reported prevalence of autism in the registry studies ranged from 1.8 to 424.6 per 10 000. A meta-analysis of 18 of the studies from mainland China (excluding a large nationwide study with the lowest prevalence of autism) with a range in rates from 2.8 to 30.4 per 10 000 generated an estimated pooled prevalence of autism of 12.8 per 10 000 (95%CI, 9.4 to 17.5). The pooled prevalence of ASD estimated from 5 of these studies (which had a range in rates from 7.3 to 75.3 per 10 000) was 24.5 per 10000 (95%CI, 10.4 to 57.4). The reported prevalence of autism varied substantially by gender, location of residence, date of publication, and source of the sample. CONCLUSION: The huge difference between the rates for autism reported from registry systems in Hong Kong and Taiwan (a 200-fold difference) and the large differences in rates reported from community-based screening studies in mainland China (a 10- to 15-fold difference) highlight the urgent need for establishing standardized methods for estimating the prevalences of autism and ASD. Until these methodological improvements have been made, it will not be possible to develop evidence-based prevention and treatment strategies for the management of these uncommon but seriously disabling conditions.