Prevalence per 1000¹ of ASD by three SES indicators based on census block group of residence.

<p>¹Thin bars indicate 95% confidence intervals. Within each SES indicator, both the trend test and χ² tests were significant at p<0.0001. ²MHI refers to median household income.</p

Prevalence (95% CI^a) of ASD per 1,000 8-Year-Olds and Ratios of ASD Prevalence by SES^b, Stratified by Race/Ethnicity^c.

a<p>CI = confidence interval.</p>b<p>Socioeconomic Status (SES) is indicated by the percentage of families with incomes above the federal poverty level who had children in the census block group of the index child, divided into population SES tertiles.</p>c<p>The following differences in prevalence between ethnic group were statistically significant at p<0.05:</p><p>Overall: Non-Hispanic White versus Non-Hispanic Black; Non-Hispanic White versus Hispanic; Non-Hispanic Black versus Asian; and Hispanic versus Asian. In addition, the overall prevalence of ASD differs at p<0.05 across race/ethnic groups.</p><p>Low SES: Non-Hispanic White versus Non-Hispanic Black; Non-Hispanic White versus Hispanic; and Non_Hispanic White versus Asian. In addition, within the low SES stratum, the prevalence of ASD differs at p<0.05 across race/ethnic groups.</p><p>Medium SES: Non-Hispanic Black versus Hispanic.</p><p>High SES: Non-Hispanic White versus Non-Hispanic Black; Non-Hispanic White versus Asian; and Hispanic versus Asian. In addition, within the high SES stratum, the prevalence of ASD differs at p<0.05 across race/ethnic groups.</p

Socioeconomic Indicators for ASD Cases and the Population of 8-Year-Old Children in the Surveillance Area.

a<p>Based on 2000 Census data.</p>b<p>Poverty areas include census block groups in which more than 20% of families with children have incomes below the poverty level <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0011551#pone.0011551-Krieger1" target="_blank">[36]</a>.</p><p>*p<0.05, comparing ASD cases to population of 8-year-old children residing in the surveillance area.</p

Demographic Characteristics of ASD Cases, Population of 8-Year-Old Children in the Surveillance Area and Overall United States Population of 8-Year-Old Children.

a<p>Based on 2000 Census data.</p><p>*p<0.05, comparing ASD cases to population of 8-year-old children residing in the surveillance area.</p><p>**p<0.05, comparing population of 8-year-old children residing in the surveillance area to United States population of 8-year-old children according to 2000 Census data.</p

Multivariable logistic regression analysis for risk factors for NDDs^#.

<p>Multivariable logistic regression analysis for risk factors for NDDs<a href="http://www.plosmedicine.org/article/info:doi/10.1371/journal.pmed.1002615#t005fn001" target="_blank">^#</a>.</p

Study recruitment profile.

<p>Study recruitment profile.</p

Background characteristics of study participants.

<p>Background characteristics of study participants.</p

Prevalence estimates of NDDs for the five study districts according to age categories^*.

<p>Prevalence estimates of NDDs for the five study districts according to age categories^{<a href="http://www.plosmedicine.org/article/info:doi/10.1371/journal.pmed.1002615#t004fn001" target="_blank">*</a>}.</p