Abstract
BackgroundsWhether there is a true increase in autism spectrum disorder (ASD) frequency or not remains unclear. Additionally, the rates of co-existing neurodevelopmental disorders (NDD) in a total population sample has not been fully examined before. Therefore, using a total population sample in Japan, we aimed to estimate the prevalence and cumulative incidence of autism spectrum disorder (ASD) annually, to determine whether there is a true increase in ASD prevalence by estimating the cumulative incidence of ASD annually, and to examine the rates of co-existing neurodevelopmental disorders (NDD).MethodIn this cross-sectional sequential design study, all 5-year-old children in the catchment area underwent the screening annually from the year 2013–2016. Screen-positive children were invited to participate in a comprehensive assessment, including child and parent interview, behavioral observation, and cognitive and motor function testing. All cases were reviewed by a multidisciplinary research team.ResultsCaregivers of 3954 children returned the screening, among which 559 children underwent the assessment with 87 children receiving an ASD diagnosis. Adjusted ASD prevalence was 3.22% (95% confidence interval (CI) 2.66–3.76%). The male to female ratio of the crude prevalence was 2.2:1. The cumulative incidence of ASD up to 5 years of age for the total study years was 1.31% (95% CI 1.00–1.62%). A generalized linear model revealed no significant linear trends in 5-year cumulative incidence over the study years. Only 11.5% of children had ASD alone; the remaining 88.5% were found to have at least one co-existing NDD.LimitationsModest sample size for a total population study.ConclusionsOur findings demonstrate the stability of the 5-year cumulative incidence of ASD, implying no true rise in ASD incident cases over the 4-year study period in the study catchment area. High rates of co-existing NDDs reflect the importance of investigating broad developmental challenges in children with ASD.
Highlights
The US Centers for Disease Control and Prevention has most recently reported an increase in the autism spectrum disorder (ASD) prevalence at 1 in 59 children [1] from that at 1 in 68 children in its previous report [2]
Our findings demonstrate the stability of the 5-year cumulative incidence of ASD, implying no true rise in ASD incident cases over the 4-year study period in the study catchment area
Using rigorous epidemiological methods to identify cases (ASD in this study) in a target population that includes all individuals at risk of developing conditions over significant periods (4 years in this study), our findings suggest that ASD is a common childhood-onset neurodevelopmental disorders (NDD) with stable prevalence and incidence estimates
Summary
The US Centers for Disease Control and Prevention has most recently reported an increase in the autism spectrum disorder (ASD) prevalence at 1 in 59 children [1] from that at 1 in 68 children in its previous report [2]. This trend is corroborated by epidemiological studies conducted in Asian countries [3, 4], consistently reporting that the ASD prevalence is higher than that previously reported in each country. A study led by the Health Resources and Service Administration using the 2016 National Survey of Children’s Health revealed that the ASD prevalence based on parent reports was 2.5% in the USA [6], supporting the findings from Kim et al ’s study
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