Objectives: Increased risk of autism with the increment of urbanization has been documented in developed countries. However, very few studies in developing countries focused on this topic. By using Chinese nationally representative large dataset, we investigated the association between urbanicity and autism among children aged 0-17 years in China. Also, we analyzed whether there existed a sexually dimorphic effect on this association. Methods: Data from the Second National Sample Survey on Disability (SNSSD) was used in this study, and 616,940 children was selected for analysis. Autism was measured by experienced psychiatrists according to The International Statistical Classification of Diseases and Related Health Problems 10th Revision Symptom Checklist for Mental Disorders. Logistic regression models allowing for multiple demographic and socioeconomic covariates were used to evaluate the association between the level of urbanization and autism in children. Results: Compared with children in low level of urbanization areas, those in high urbanization level areas was 2.12 (95%CI: 1.28, 3.49) times more likely to develop autism, and 1.85(95%CI: 1.21, 2.84) times for those in moderate level of urbanization areas. Stratified analyses found that all observed associations were only in male children, not in female children. Conclusions: Our findings suggested that higher level of urbanicity was associated with higher risk of autism in children. This association was only present in male children, not in female children.

Introduction

Urbanization is a major socio-ecological change and progress in human society, mainly taking place at a massive scale in low- and middle-income countries (Lederbogen et al., 2011). Currently, 55% humans live in urban areas, and this proportion will increase to 68% by 2050, with close to 90% of the increase occurring in Asia and Africa regions (Nations, 2018). Although urbanicity generates wealthy, productivity, improved sanitary conditions and better health care services, it also results in stressful social environment, greater social disparities and serious pollution(Dye, 2008; Lederbogen et al., 2011; Li et al., 2016). These factors related to both health benefits and risks, but mental health is negatively affected (Lederbogen et al., 2011). Recently, urbanization has been well-established to increase the risk of mental health problems, which strongly implicated in mood and anxiety disorders, depression and psychosis (McKenzie, Murray, & Booth, 2013; Sundquist, Frank, & Sundquist, 2004; Vassos, Pedersen, Murray, Collier, & Lewis, 2012). Autism is a neurodevelopmental disorder characterized by social interaction and communication impairments and the restricted and repetitive behaviors (M. B. J. E. c. Lauritsen & psychiatry, 2013).