A Letter to the Editor

Autism spectrum disorders (ASD) is one of the most common and serious neurodevelopmental disorders resulting in a substantial burden for individuals, families, and society (Lord et al., 2018). Although the United States (US) have been monitoring the ASD prevalence, whether the prevalence has continued to increase, decrease, fluctuate or reached a stable level remained unclear during the COVID-19 pandemic.

Methods

We have requested the 2016-2021 National Survey of Children’s Health (NSCH) with permission (reference number: 11,275 and 11,879) which is a population-based, nationally representative survey in the US. The 2020-2021 NSCH was fielded from June 2020 to January 2022 after the COVID-19 pandemic. The combined 2016-2021 NSCH sample size included 225 443 children of which 194 051 children aged 3-17 years. 1979 (1.01%) were excluded because of missing information on diagnosis and socio-economic characteristics, resulting in a final sample of 192 072 children (details shown in eFigure). Data are collected from parents or primary caregivers through web- or paper-based questionnaires, and NSCH ask if the parent/caregiver was ever told that the child has ASD (“ever ASD”) and includes a follow-up question asking whether the child currently has ASD (“current ASD”). The South China Normal University Institutional Review Board deemed this study exempt from review.

We estimated weighted ever and current ASD prevalence adjusting for child’s age, sex, race/ethnicity, highest parental education, and household income level, along with 95% confidence interval (CI), for each year between 2016 and 2021. We performed polynomial regression models to assess linearity/nonlinearity in the time trend, and we performed stratified analyses for several subpopulations (stratified by child’s age, sex and race/ethnicity).

Results

The weighted ever and current ASD prevalence were 2.7% (95%CI, 2.4-3.0%) and 2.5% (95%CI, 2.2-2.8%) in 2016, 3.2% (95%CI, 2.5-3.9%) and 3.1% (95%CI, 2.4-3.8%) in 2017, 2.9% (95%CI, 2.5-3.3%) and 2.8% (95%CI, 2.4-3.2%) in 2018, 3.3% (95%CI, 2.8-3.8%) and 3.1% (95%CI, 2.7-3.6%) in 2019, 2.9% (95%CI,2.6-3.3%) and 2.8% (95%CI, 2.4-3.1%) in 2020, 3.4% (95%CI, 3.0-3.8%) and 3.1% (95%CI, 2.7-3.4%) in 2021, respectively (Table 1).

Table 1 Prevalence of ASD in children and adolescents in the US from 2016 to 2021 a
Full size table

We observed non-significant time trends of prevalence in both overall and stratified populations (linear, quadratic, cubic trends: all P > 0.05) despite of some marginal significance (0.05< P <0.1).

Discussion

We did not observe linear or nonlinear trends of the ASD prevalence during the 2016-2021 periods. The current ASD prevalence experienced a 0.3% drop from 2019 to 2020 but a 0.3% uptick in 2021, suggesting a stable trend during the COVID-19 pandemic. This could be partly explained by the similar proportions of young children receiving developmental screenings before and after the pandemic’s onset (Lebrun-Harris et al., 2022). However, the prevalence might be underestimated due to less timely diagnosis after screening during the pandemic, and the dynamic and long-term effects of COVID-19 on ASD prevalence should be captured in future studies. Our findings shed lights on the need for the implementation of validated telehealth (i.e., standardized online diagnostic process), which could reach a wide range of families to monitor ASD prevalence during the COVID-19 era.

However, caution should be taken since the ASD prevalence and its trend reported in different national surveys (Guifeng Xu, 2018; Lebrun-Harris et al., 2022; Maenner et al., 2021; Qian Li et al., 2022) showed inconsistent data reports (Li & He, 2022; Qian Li et al., 2022). The National Health Interview Survey (Guifeng Xu, 2018; Qian Li et al., 2022) estimates the prevalence based on ever having received a diagnosis, while the NSCH obtained information of both ever and current diagnosis. The ASD prevalence of these two surveys were higher than those reported from the Autism and Developmental Disabilities Monitoring Network (Maenner et al., 2021), which monitors prevalence only among children aged 4 or 8 years. In order to overcome the differences of methodologies or sampling strategies across different surveys and facilitate the researchers’ interpretation of the ASD prevalence, the Centre of Disease Control and Prevention might consider combining these data together by subtle statistical techniques to predict an aggregated prevalence to the public, or recommend the most suitable scenarios for each source.