A space-time analysis of disparities in age at diagnosis of autism spectrum disorder: environmental and socioeconomic risk factors

Introduction Early diagnosis of autism is a critical step for gaining early intervention. The earlier interventions begin, the greater chance to reduce symptoms of autism over the lifespan. Despite the improvement in early diagnosis, age at diagnosis varies by residential locations. In order to improve early screening services, this study aims to identify geographic clusters of early and late diagnosis of autism, in addition, it is aimed to compare cases inside the clusters with the rest of the province on characteristics and socioeconomic factors. Materials and methods Survey data were collected from 163 autistics born from 1996 to 2011 in Isfahan Province, Iran. As this study found diagnosis of autism occur at an earlier age among children, who on average every 2.5 months increased for each year of age, distance from regression line has been used to determine how early a case was diagnosed compared to other identified cases. After dividing cases into 5 classes based on their distances from the regression line, the ordinal based space-time scan statistic in SaTScan was used to identify geographic areas within specific time periods that have significantly elevated proportions of autistic children who received diagnosis at the earlier or later stages. Results The space-time analysis identified two geographic areas that age of diagnosis was inconsistent with the overall study area, the first area has an early diagnosis in central part of Isfahan megacity between 1998 and 2006 (P = .001), the second area shows to have a late diagnosis centered by Najafabad from 2010 through 2015 (P = .007). Conclusions The result of our spatial analysis can be used to evaluate the performance of diagnosis services and additionally provide information to target specific at-risk population for further interventions.