Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada.
Public Health Agency of Canada, Ottawa, Ontario, Canada.
Health Promot Chronic Dis Prev Can. 2017 Jan;37(1):1-23. doi: 10.24095/hpcdp.37.1.01.
The number of children diagnosed with autism spectrum disorder (ASD) has been rapidly rising in the past decade. The etiology of this disorder, however, is largely unknown, although the environmental relative to the genetic contribution is substantial. We conducted a scoping review to comprehensively assess the current state of knowledge of the environmental factors present from preconception to early life associated with ASD, and to identify research gaps.
We searched electronic databases MEDLINE, PsycINFO and ERIC for articles on potential risk factors or protective factors from the physical and social environments associated with ASD and its subclassifications published between 1 January, 2003, and 12 July, 2013. We categorized articles into broad themes: chemical, physiological, nutritional and social factors, based on environmental exposure.
We identified over 50 000 publications, but after ineligible studies were screened out, 315 articles remained. Most of these studies examined physiological factors, followed closely by chemical factors, and to a much lesser extent, nutritional and social factors, associated with ASD. Despite a vast literature and many heterogeneous studies, several risk factors emerged consistently: chemical factors such as traffic-related air pollutants; physiological factors including advanced parental age, preterm birth, low birth weight, hyperbilirubinemia and clustering of pregnancy complications; and maternal immigrant status. Despite extensive research on vaccines, findings overwhelmingly demonstrate no support for an association with ASD.
The lack of consistency, temporality and specificity of associations between environmental factors and ASD remains the largest barrier to establishing causal relationships. More robust research is required to resolve inconsistencies in the literature. Future research should explore underlying mechanisms of associations between the risk factors that we identified and ASD.
在过去的十年中，被诊断出患有自闭症谱系障碍（ASD）的儿童数量迅速增加。然而，尽管环境对遗传的贡献很大，但这种疾病的病因在很大程度上仍是未知的。我们进行了范围界定审查，以全面评估从受孕前到生命早期与 ASD 相关的环境因素的现有知识状况，并确定研究空白。
我们搜索了电子数据库 MEDLINE、PsycINFO 和 ERIC，以获取与 ASD 及其亚分类相关的物理和社会环境中潜在风险因素或保护因素的文章，这些文章的发表时间为 2003 年 1 月 1 日至 2013 年 7 月 12 日。我们根据环境暴露情况将文章分为广泛的主题：化学、生理、营养和社会因素。
我们确定了 50000 多篇出版物，但在筛选出不合格的研究后，仍有 315 篇文章保留下来。这些研究大多研究了生理因素，其次是化学因素，而营养和社会因素则研究得较少，与 ASD 相关。尽管有大量文献和许多异质研究，但仍出现了一些一致的风险因素：化学因素，如与交通相关的空气污染物；生理因素，包括父母年龄较大、早产、低出生体重、高胆红素血症和妊娠并发症的聚集；以及产妇移民身份。尽管对疫苗进行了广泛的研究，但研究结果压倒性地表明，疫苗与 ASD 没有关联。
环境因素与 ASD 之间的关联缺乏一致性、时间性和特异性，这仍然是确定因果关系的最大障碍。需要更强大的研究来解决文献中的不一致问题。未来的研究应该探索我们确定的风险因素与 ASD 之间关联的潜在机制。
