摘要：Objectives. To describe the association between indicators of socioeconomic status (SES) and the prevalence of autism spectrum disorder (ASD) in the United States during the period 2002 to 2010, when overall ASD prevalence among children more than doubled, and to determine whether SES disparities account for ongoing racial and ethnic disparities in ASD prevalence. Methods. We computed ASD prevalence and 95% confidence intervals (CIs) from population-based surveillance, census, and survey data. We defined SES categories by using area-level education, income, and poverty indicators. We ascertained ASD in 13 396 of 1 308 641 8-year-old children under surveillance. Results. The prevalence of ASD increased with increasing SES during each surveillance year among White, Black, and Hispanic children. The prevalence difference between high- and low-SES groups was relatively constant over time (3.9/1000 [95% CI = 3.3, 4.5] in 2002 and 4.1/1000 [95% CI = 3.6, 4.6] in the period 2006–2010). Significant racial/ethnic differences in ASD prevalence remained after stratification by SES. Conclusions. A positive SES gradient in ASD prevalence according to US surveillance data prevailed between 2002 and 2010, and racial and ethnic disparities in prevalence persisted during this time among low-SES children. Population-based studies of the prevalence of autism spectrum disorder (ASD) in the United States have reported notable differences among selected racial and ethnic groups, with prevalence generally found to be higher among non-Hispanic White children relative to both non-Hispanic Black and Hispanic children. 1–7 Studies in the United States 8–10 and in some, 11,12 but not other, 13,14 countries have also found a positive socioeconomic status (SES) gradient in ASD prevalence, with prevalence increasing with indicators of increasing socioeconomic advantage. For example, in a previous analysis of public health surveillance data for children in communities included in the Centers for Disease Control and Prevention’s Autism and Developmental Disabilities Monitoring (ADDM) Network in 2002 and 2004, we found a dose–response association between SES and ASD prevalence, and a prevalence nearly 70% higher among children in the highest relative to the lowest SES tertile of the population (prevalence ratio = 1.69; 95% confidence interval [CI] = 1.55, 1.83). 10 The SES findings for ASD stand in sharp contrast to those for intellectual disability and childhood disabilities generally, which consistently show an excess prevalence among children of low SES. 15 Taken together, the US findings of racial/ethnic and socioeconomic variation in prevalence suggest potential underascertainment of ASD in economically disadvantaged groups, and raise the question of whether the ongoing racial and ethnic disparities in ASD prevalence are confounded by SES. Since our earlier analysis of SES disparities in ASD prevalence based on ADDM Network findings, 10 the estimated prevalence of ASD overall has more than doubled, from 6.6 per 1000 8-year-old children in 2002 16 to 14.7 in 2010. 1 Whether the increase in prevalence occurred across all SES strata is not known. If the increase occurred disproportionally among children of low SES, perhaps because of expanded screening and improved access to ASD diagnostic and treatment services over time, we would expect to see a diminution of the SES gradient in ASD prevalence. The present study analyzed ADDM Network data for the period 2002 to 2010 to address 2 main questions: (1) Did the SES gradient in ASD prevalence persist in each surveillance year from 2002 through 2010? and (2) Were the racial and ethnic differences in ASD prevalence that have been previously documented present within SES strata throughout the period? An affirmative answer to the second question would suggest that racial and ethnic disparities in ASD prevalence are not readily explained by racial/ethnic disparities in available indicators of SES. Additional questions we sought to answer were whether a positive SES gradient was present over time among subgroups defined by race, ethnicity, sex, and co-occurrence of intellectual disability, and among ASD cases ascertained from different sources (health care, school, and both health care and school). In our previous study, 10 we had hypothesized that a positive SES gradient would not be found among cases ascertained from school sources because special education services for autism should be accessible to all school-aged children with ASD in the United States, whereas specialized health and autism therapeutic services are not universally available and accessible. However, in our previous study, based on surveillance years 2002 and 2004, we found the SES gradient to be similar for cases identified through health care and school sources. 10
