Monday, May 29, 2023
| Site | Surveillance area description | Denominator | No. of children aged 4 yrs with ASD | ASD prevalence(95% CI)* | % of children who had an ASD diagnosis | % of children who had ASD special education eligibility | % of children who had an ASD ICD code |
|---|---|---|---|---|---|---|---|
| Arizona | Part of one county in metropolitan Phoenix | 13,929† | 141 | 10.1 (8.6–11.9) | 92.9 | 24.1 | 44.0 |
| Arkansas | 21 counties in central Arkansas | 15,387 | 183 | 11.9 (10.3–13.7) | 92.3 | 17.5 | 79.2 |
| California | Part of one county in metropolitan San Diego | 16,796† | 698 | 41.6 (38.6–44.7) | 81.2 | 88.3 | 54.7 |
| Georgia | Two counties in metropolitan Atlanta | 23,040 | 340 | 14.8 (13.3–16.4) | 75.0 | 48.2 | 60.0 |
| Maryland | Five counties in suburban Baltimore | 19,818 | 233 | 11.8 (10.3–13.4) | 70.4 | 51.9 | 73.4 |
| Minnesota | Parts of three counties in the Twin Cities metropolitan area | 10,529† | 240 | 22.8 (20.1–25.8) | 48.3 | 80.4 | 47.5 |
| Missouri | Five counties in metropolitan St. Louis | 24,521 | 338 | 13.8 (12.4–15.3) | 95.6 | 3.3 | 97.6 |
| New Jersey | Part of two counties in New York metropolitan area | 17,286† | 342 | 19.8 (17.8–22.0) | 98.0 | 17.8 | 73.7 |
| Tennessee | 11 counties in middle Tennessee | 25,335 | 497 | 19.6 (18.0–21.4) | 75.1 | 39.0 | 89.7 |
| Utah | Three counties in northern Utah | 25,064 | 229 | 9.1 (8.0–10.4) | 76.9 | 24.0 | 87.8 |
| Wisconsin | Eight counties in southeastern Wisconsin | 28,689 | 513 | 17.9 (16.4–19.5) | 80.3 | 25.5 | 77.2 |
| Total | 220,394 | 3,754 | 17.0 (16.5–17.6) | 80.5 | 42.9 | 72.0 |
Table 1. Prevalence of autism spectrum disorder per 1,000 children aged 4 years and percentage of children who had an autism spectrum disorder diagnosis, special education eligibility, or an International Classification of Diseases code — Autism and Developmental Disabilities Monitoring Network, 11 sites, 2018
Abbreviations: ASD = autism spectrum disorder; CI = confidence interval; ICD = International Classification of Diseases.
*95% CIs were calculated using the Wilson score method.
†Denominator excludes school districts that were not included in the surveillance area, calculated from National Center for Education Statistics enrollment counts of kindergarteners during the 2018–19 school year.
| Site | Male ASD prevalence (95% CI)* | Female ASD prevalence (95% CI)* | Male-to-female prevalence ratio (95% CI)*,† |
|---|---|---|---|
| Arizona | 16.6 (13.8–19.8) | 3.5 (2.4–5.2) | 4.7 (3.1–7.3) |
| Arkansas | 19.2 (16.4–22.5) | 4.1 (2.9–5.9) | 4.6 (3.2–6.8) |
| California | 63.6 (58.6–68.9) | 18.2 (15.5–21.3) | 3.5 (2.9–4.2) |
| Georgia | 23.5 (20.9–26.5) | 5.7 (4.5–7.3) | 4.1 (3.1–5.4) |
| Maryland | 18.2 (15.8–21.0) | 5.0 (3.8–6.6) | 3.7 (2.7–5.0) |
| Minnesota | 34.8 (30.2–40.0) | 10.6 (8.1–13.7) | 3.3 (2.4–4.4) |
| Missouri | 20.2 (17.9–22.8) | 7.1 (5.7–8.8) | 2.8 (2.2–3.6) |
| New Jersey | 30.3 (26.9–34.1) | 8.8 (7.0–11.0) | 3.5 (2.7–4.5) |
| Tennessee | 29.2 (26.4–32.2) | 9.8 (8.2–11.7) | 3.0 (2.4–3.7) |
| Utah | 13.7 (11.8–15.9) | 4.3 (3.3–5.7) | 3.2 (2.3–4.3) |
| Wisconsin | 26.2 (23.7–28.9) | 9.0 (7.6–10.7) | 2.9 (2.4–3.5) |
| Total | 25.9 (25.0–26.9) | 7.7 (7.2–8.2) | 3.4 (3.1–3.6) |
Table 2. Prevalence of autism spectrum disorder per 1,000 children aged 4 years, by sex — Autism and Developmental Disabilities Monitoring Network, 11 sites, United States, 2018
Abbreviations: ASD = autism spectrum disorder; CI = confidence interval.
*95% CIs were calculated using the Wilson score method.
†Prevalence significantly higher among males than females at all sites (prevalence ratio 95% CIs do not include 1.0).
| Site | ASD prevalence (95% CI)† | Prevalence ratio (95% CI) | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| White, non-Hispanic | Black, non-Hispanic | Hispanic | Asian/Pacific Islander | American Indian/Alaska Native | White, non-Hispanic to Black, non-Hispanic | White, non-Hispanic to Hispanic | White, non-Hispanic to Asian/Pacific Islander | Black, non-Hispanic to Hispanic | Black, non-Hispanic to Asian/Pacific Islander | Hispanic to Asian/Pacific Islander | |
| Arizona | 13.2 (10.6–16.4) | —§ | 8.5 (6.5–11.3) | —§ | —§ | —§ | 1.6 (1.1–2.2)¶ | —§ | —§ | —§ | —§ |
| Arkansas | 11.4 (9.5–13.7) | 10.5 (7.8–14.2) | —§ | —§ | —§ | 1.1 (0.8–1.5) | —§ | —§ | —§ | —§ | —§ |
| California | 26.0 (21.9–30.8) | 30.6 (23.1–40.5) | 45.5 (41.1–50.3) | 41.7 (34.3–50.6) | —§ | 0.8 (0.6–1.2) | 0.6 (0.5–0.7)¶ | 0.6 (0.5–0.8)¶ | 0.7 (0.5–0.9)¶ | 0.7 (0.5–1.0) | 1.1 (0.9–1.4) |
| Georgia | 12.0 (9.6–15.0) | 17.1 (14.7–20.0) | 10.0 (7.7–13.0) | 17.7 (12.9–24.3) | —§ | 0.7 (0.5–0.9)¶ | 1.2 (0.9–1.7) | 0.7 (0.5–1.0) | 1.7 (1.3–2.3)¶ | 1.0 (0.7–1.4) | 0.6 (0.4–0.9)¶ |
| Maryland | 9.1 (7.5–11.1) | 13.5 (10.6–17.1) | 8.8 (5.5–14.0) | 15.5 (10.8–22.3) | —§ | 0.7 (0.5–0.9)¶ | 1.0 (0.6–1.7) | 0.6 (0.4–0.9)¶ | 1.5 (0.9–2.6) | 0.9 (0.6–1.3) | 0.6 (0.3–1.0) |
| Minnesota | 16.6 (13.6–20.3) | 23.5 (18.4–30.0) | 24.4 (17.0–34.8) | 30.8 (21.3–44.5) | —§ | 0.7 (0.5–1.0)¶ | 0.7 (0.5–1.0) | 0.5 (0.4–0.8)¶ | 1.0 (0.6–1.5) | 0.8 (0.5–1.2) | 0.8 (0.5–1.3) |
| Missouri | 13.1 (11.4–14.9) | 11.5 (9.2–14.5) | —§ | 30.0 (20.7–43.3) | —§ | 1.1 (0.9–1.5) | —§ | 0.4 (0.3–0.6)¶ | —§ | 0.4 (0.3–0.6)¶ | —§ |
| New Jersey | 15.2 (12.0–19.2) | 20.0 (16.6–24.1) | 20.6 (17.4–24.4) | 16.4 (10.1–26.5) | —§ | 0.8 (0.6–1.0) | 0.7 (0.6–1.0)¶ | 0.9 (0.5–1.6) | 1.0 (0.8–1.2) | 1.2 (0.7–2.0) | 1.3 (0.8–2.1) |
| Tennessee | 16.8 (14.9–18.9) | 21.1 (17.4–25.5) | 24.8 (20.1–30.5) | 20.0 (12.5–31.8) | —§ | 0.8 (0.6–1.0)¶ | 0.7 (0.5–0.9)¶ | 0.8 (0.5–1.4) | 0.9 (0.6–1.1) | 1.1 (0.6–1.7) | 1.2 (0.7–2.1) |
| Utah | 7.7 (6.5–9.1) | —§ | 10.8 (8.3–13.9) | 9.9 (5.7–17.2) | —§ | —§ | 0.7 (0.5–1.0)¶ | 0.8 (0.4–1.4) | —§ | —§ | 1.1 (0.6–2.0) |
| Wisconsin | 12.7 (11.1–14.5) | 18.1 (15.0–22.0) | 30.4 (25.7–36.0) | 21.9 (15.8–30.3) | —§ | 0.7 (0.6–0.9)¶ | 0.4 (0.3–0.5)¶ | 0.6 (0.4–0.8)¶ | 0.6 (0.5–0.8)¶ | 0.8 (0.6–1.2) | 1.4 (1.0–2.0) |
| Total | 12.9 (12.3–13.6) | 16.6 (15.4–17.8) | 21.1 (19.8–22.4) | 22.7 (20.3–25.4) | 11.5 (7.2–18.4) | 0.8 (0.7–0.9)¶ | 0.6 (0.6–0.7)¶ | 0.6 (0.5–0.6)¶ | 0.8 (0.7–0.9)¶ | 0.7 (0.6–0.8)¶ | 0.9 (0.8–1.1) |
Table 3. Prevalence of autism spectrum disorder per 1,000 children aged 4 years, by race/ethnicity* — Autism and Developmental Disabilities Monitoring Network, 11 sites, 2018
Abbreviations: ASD = autism spectrum disorder; CI = confidence interval.
*Excludes children of other (including multiracial) or unknown race.
†95% CIs were calculated using the Wilson score method.
§Estimate was suppressed because standard error for prevalence was ≥30% of estimate or prevalence ratio was based on an estimate that was suppressed.
¶Significant prevalence ratio (unrounded 95% CIs do not include 1.0).
| Site/Characteristic | No. with intellectual disability information | With co-occurring intellectual disability |
|---|---|---|
| No. (%)* | ||
| Site | ||
| Arizona | 94 | 54 (57.4) |
| Arkansas | 121 | 75 (62.0) |
| California | 542 | 125 (23.1) |
| Georgia | 192 | 115 (59.9) |
| Maryland | 118 | 90 (76.3) |
| Minnesota | 159 | 90 (56.6) |
| Missouri | 63 | 31 (49.2) |
| New Jersey | 205 | 114 (55.6) |
| Tennessee | 241 | 162 (67.2) |
| Utah | 90 | 53 (58.9) |
| Wisconsin | 178 | 124 (69.7) |
| Total | 2,003 | 1,033 (51.6) |
| Sex | ||
| Female | 434 | 230 (53.0) |
| Male | 1,569 | 803 (51.2) |
| Race/Ethnicity † | ||
| White, non-Hispanic | 744 | 371 (49.9) |
| Black, non-Hispanic | 394 | 264 (67.0) |
| Asian/Pacific Islander | 169 | 81 (47.9) |
| Hispanic | 554 | 252 (45.5) |
| Median household income tertile§ | ||
| Low | 685 | 411 (60.0) |
| Middle | 679 | 359 (52.9) |
| High | 631 | 256 (40.6) |
Table 4. Presence of co-occurring intellectual disability among children aged 4 years with autism spectrum disorder and available intellectual disability information, by site and selected characteristics — Autism and Developmental Disabilities Monitoring Network, 11 sites, 2018
*Chi-square p values for comparisons: male to female: p = 0.54; White to Asian/Pacific Islander: p = 0.71; White to Hispanic: p = 0.13; White to Black, Asian/Pacific Islander to Black, Hispanic to Black: p<0.01; Cochran-Armitage test for trend for median household income tertile: p<0.01.
†Excludes children of other (including multiracial) or unknown race.
§Limited to 3,534 children with median household income information (218 children were not able to be matched to census tract and two children were living in census tracts with suppressed median household income estimates).
| Site/Characteristic | No. with evaluation | Evaluated by age 36 mos |
|---|---|---|
| No. (%)* | ||
| Site | ||
| Arizona | 141 | 115 (81.6) |
| Arkansas | 182 | 124 (68.1) |
| California | 679 | 504 (74.2) |
| Georgia | 285 | 211 (74.0) |
| Maryland | 183 | 152 (83.1) |
| Minnesota | 228 | 156 (68.4) |
| Missouri | 334 | 248 (74.3) |
| New Jersey | 338 | 250 (74.0) |
| Tennessee | 476 | 322 (67.6) |
| Utah | 202 | 134 (66.3) |
| Wisconsin | 473 | 314 (66.4) |
| Total | 3,521 | 2,530 (71.9) |
| Sex | ||
| Female | 791 | 564 (71.3) |
| Male | 2,730 | 1,966 (72.0) |
| Race/Ethnicity† | ||
| White, non-Hispanic | 1,393 | 1,003 (72.0) |
| Black, non-Hispanic | 706 | 499 (70.7) |
| Asian/Pacific Islander | 280 | 199 (71.1) |
| Hispanic | 894 | 653 (73.0) |
| Co-occurring intellectual disability | ||
| Intellectual disability | 1,028 | 803 (78.1) |
| No intellectual disability | 967 | 770 (79.6) |
| Unknown | 1,526 | 957 (62.7) |
| Median household income tertile § | ||
| Low | 1,274 | 911 (71.5) |
| Middle | 1,165 | 860 (73.8) |
| High | 999 | 750 (75.1) |
Table 5. Percentage of children aged 4 years with autism spectrum disorder who had earliest recorded evaluation by age 36 months, by site and selected characteristics — Autism and Developmental Disabilities Monitoring Network, 11 sites, United States, 2018
*Chi-square p values for comparisons: sex: p = 0.73; race: p = 0.75; intellectual disability to no intellectual disability: p = 0.44; intellectual disability to unknown, no intellectual disability to unknown: p<0.01; low to high median household income: p = 0.06; Cochran-Armitage test for trend for median household income tertile: p = 0.45.
†Excludes children of other (including multiracial) or unknown race.
§Limited to 3,534 children with median household income information (218 children were not able to be matched to census tract, and two children were living in census tracts with suppressed median household income estimates).
| Site | Low MHI tertile | Middle MHI tertile | High MHI tertile |
|---|---|---|---|
| Rate (95% CI)† | Rate (95% CI)† | Rate (95% CI)† | |
| Arizona§ | 9.0 (7.0–11.6) | 6.1 (4.4–8.6) | 5.0 (3.4–7.4) |
| Arkansas | 8.9 (7.2–11.0) | 10.6 (8.1–14.0) | 15.0 (9.1–24.6) |
| California§ | 36.3 (31.5–41.7) | 27.6 (24.2–31.6) | 26.1 (22.9–29.7) |
| Georgia | 9.3 (7.5–11.5) | 9.7 (7.7–12.2) | 12.2 (9.8–15.1) |
| Maryland | 7.4 (4.6–12.0) | 8.3 (6.4–10.9) | 7.8 (6.3–9.7) |
| Minnesota | 18.1 (14.3–23.0) | 15.8 (12.6–19.8) | 14.6 (11.4–18.6) |
| Missouri§ | 9.4 (7.5–11.7) | 12.3 (10.2–14.9) | 13.2 (10.9–16.1) |
| New Jersey | 17.3 (14.7–20.3) | 19.9 (15.6–25.5) | 18.3 (15.1–22.3) |
| Tennessee§ | 14.6 (12.3–17.2) | 15.6 (13.3–18.2) | 10.1 (7.8–13.0) |
| Utah§ | 11.9 (8.9–15.9) | 5.9 (4.6–7.7) | 4.4 (3.3–5.8) |
| Wisconsin§ | 14.2 (12.2–16.5) | 12.3 (10.2–14.7) | 9.3 (7.4–11.7) |
| Total§ | 13.8 (13.0–14.6) | 12.8 (12.1–13.7) | 11.7 (11.0–12.5) |
Table 6. Cumulative incidence of autism spectrum disorder diagnosis or eligibility by age 48 months per 1,000 children aged 4 years, by site and median household income tertile* — Autism and Developmental Disabilities Monitoring Network, 11 sites, United States, 2018
Abbreviations: CI = confidence interval; MHI = median household income.
*Limited to 3,534 children with MHI information (218 children were not able to be matched to census tract and two children were living in census tracts with suppressed MHI estimates).
†95% CIs were calculated using the Wilson score method.
§Cochran-Armitage test for trend p<0.05.
| Site | No. of children aged 4 yrs with suspected ASD | Suspected ASD prevalence rate (95% CI)* | Ratio of ASD prevalence to suspected ASD prevalence |
|---|---|---|---|
| Arizona | 68 | 4.9 (3.9–6.2) | 2:1 |
| Arkansas | 72 | 4.7 (3.7–5.9) | 3:1 |
| California | 6 | 0.4 (0.2–0.8) | 116:1 |
| Georgia | 69 | 3.0 (2.4–3.8) | 5:1 |
| Maryland | 48 | 2.4 (1.8–3.2) | 5:1 |
| Minnesota | 23 | 2.2 (1.5–3.3) | 10:1 |
| Missouri | 36 | 1.5 (1.1–2.0) | 9:1 |
| New Jersey | 37 | 2.1 (1.6–2.9) | 9:1 |
| Tennessee | 33 | 1.3 (0.9–1.8) | 15:1 |
| Utah | 86 | 3.4 (2.8–4.2) | 3:1 |
| Wisconsin | 102 | 3.6 (2.9–4.3) | 5:1 |
| Total | 580 | 2.6 (2.4–2.9) | 6:1 |
Table 7. Prevalence of suspected autism spectrum disorder per 1,000 children aged 4 years — Autism and Developmental Disabilities Monitoring Network, 11 sites, United States, 2018
Abbreviations: ASD = autism spectrum disorder; CI = confidence interval.
*95% CIs were calculated using the Wilson score method.
| Characteristic | Children with ASD | Children with suspected ASD* |
|---|---|---|
| No. (%) | No. (%) | |
| Sex | ||
| Female | 830 (22.1) | 140 (24.1) |
| Male | 2,924 (77.9) | 440 (75.9) |
| Race/Ethnicity† | ||
| White, non-Hispanic | 1,487 (42.6) | 272 (49.5) |
| Black, non-Hispanic | 771 (22.1) | 127 (23.1) |
| Asian/Pacific Islander | 302 (8.6) | 25 (4.6) |
| Hispanic | 932 (26.7) | 125 (22.8) |
| Intellectual disability§ | ||
| Intellectual disability | 1,033 (51.6) | 106 (41.4) |
| Evaluation ¶ | ||
| Earliest recorded evaluation by age ≤36 mos | 2,530 (71.9) | 401 (69.1) |
| Median household income tertile** | ||
| Low | 1,309 (37.0) | 183 (32.3) |
| Middle | 1,199 (33.9) | 204 (36.0) |
| High | 1,026 (29.0) | 179 (31.6) |
Table 8. Characteristics of children aged 4 years with autism spectrum disorder and with suspected autism spectrum disorder — Autism and Developmental Disabilities Monitoring Network, 11 sites, United States, 2018
Abbreviation: ASD = autism spectrum disorder.
*Chi-square p values for comparisons: sex: p = 0.30; race: p<0.01; intellectual disability: p<0.01; evaluation: p = 0.61; Chi-square test of distribution of median household income tertile among children with ASD: p<0.01; Chi-square test of distribution of median household income tertile among children with suspected ASD: p = 0.38.
†Excludes children of other (including multiracial) or unknown race.
§Limited to children with intellectual disability data available.
¶Limited to children with an evaluation (N = 3,521 children with ASD; N = 580 children with suspected ASD).
**Limited to 3,534 children with median household income information (218 children were not able to be matched to census tract and two children were living in census tracts with suppressed median household income estimates).
This activity is intended for public health officials, pediatricians, psychiatrists, neurologists, family practice clinicians, nurses, and other clinicians caring for children with or at risk for autism spectrum disorder (ASD).
The goal of this activity is to describe prevalence of ASD, associated intellectual disability, and early identification of ASD among children aged 4 years in the United States in 2018, according to an analysis of surveillance data from all 11 Autism and Developmental Disabilities Monitoring Network (ADDM) Network sites.
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Problem/Condition: Autism spectrum disorder (ASD).
Period Covered: 2018.
Description of System: The Autism and Developmental Disabilities Monitoring Network is an active surveillance program that estimates ASD prevalence and monitors timing of ASD identification among children aged 4 and 8 years. This report focuses on children aged 4 years in 2018, who were born in 2014 and had a parent or guardian who lived in the surveillance area in one of 11 sites (Arizona, Arkansas, California, Georgia, Maryland, Minnesota, Missouri, New Jersey, Tennessee, Utah, and Wisconsin) at any time during 2018. Children were classified as having ASD if they ever received 1) an ASD diagnostic statement (diagnosis) in an evaluation, 2) a special education classification of ASD (eligibility), or 3) an ASD International Classification of Diseases (ICD) code. Suspected ASD also was tracked among children aged 4 years. Children who did not meet the case definition for ASD were classified as having suspected ASD if their records contained a qualified professional's statement indicating a suspicion of ASD.
Results: For 2018, the overall ASD prevalence was 17.0 per 1,000 (one in 59) children aged 4 years. Prevalence varied from 9.1 per 1,000 in Utah to 41.6 per 1,000 in California. At every site, prevalence was higher among boys than girls, with an overall male-to-female prevalence ratio of 3.4. Prevalence of ASD among children aged 4 years was lower among non-Hispanic White (White) children (12.9 per 1,000) than among non-Hispanic Black (Black) children (16.6 per 1,000), Hispanic children (21.1 per 1,000), and Asian/Pacific Islander (A/PI) children (22.7 per 1,000). Among children aged 4 years with ASD and information on intellectual ability, 52% met the surveillance case definition of co-occurring intellectual disability (intelligence quotient ≤70 or an examiner's statement of intellectual disability documented in an evaluation). Of children aged 4 years with ASD, 72% had a first evaluation at age ≤36 months. Stratified by census-tract–level median household income (MHI) tertile, a lower percentage of children with ASD and intellectual disability was evaluated by age 36 months in the low MHI tertile (72%) than in the high MHI tertile (84%). Cumulative incidence of ASD diagnosis or eligibility received by age 48 months was 1.5 times as high among children aged 4 years (13.6 per 1,000 children born in 2014) as among those aged 8 years (8.9 per 1,000 children born in 2010). Across MHI tertiles, higher cumulative incidence of ASD diagnosis or eligibility received by age 48 months was associated with lower MHI. Suspected ASD prevalence was 2.6 per 1,000 children aged 4 years, meaning for every six children with ASD, one child had suspected ASD. The combined prevalence of ASD and suspected ASD (19.7 per 1,000 children aged 4 years) was lower than ASD prevalence among children aged 8 years (23.0 per 1,000 children aged 8 years).
Interpretation: Groups with historically lower prevalence of ASD (non-White and lower MHI) had higher prevalence and cumulative incidence of ASD among children aged 4 years in 2018, suggesting progress in identification among these groups. However, a lower percentage of children with ASD and intellectual disability in the low MHI tertile were evaluated by age 36 months than in the high MHI group, indicating disparity in timely evaluation. Children aged 4 years had a higher cumulative incidence of diagnosis or eligibility by age 48 months compared with children aged 8 years, indicating improvement in early identification of ASD. The overall prevalence for children aged 4 years was less than children aged 8 years, even when prevalence of children suspected of having ASD by age 4 years is included. This finding suggests that many children identified after age 4 years do not have suspected ASD documented by age 48 months.
Public Health Action: Children born in 2014 were more likely to be identified with ASD by age 48 months than children born in 2010, indicating increased early identification. However, ASD identification among children aged 4 years varied by site, suggesting opportunities to examine developmental screening and diagnostic practices that promote earlier identification. Children aged 4 years also were more likely to have co-occurring intellectual disability than children aged 8 years, suggesting that improvement in the early identification and evaluation of developmental concerns outside of cognitive impairments is still needed. Improving early identification of ASD could lead to earlier receipt of evidence-based interventions and potentially improve developmental outcomes.
Autism spectrum disorder (ASD) is a developmental disability characterized by deficits in social communication and interaction and the presence of restricted interests and repetitive behaviors. Early routine screening for ASD and other developmental concerns is recommended by the American Academy of Pediatrics[1] because early evaluation, diagnosis, and evidence-based interventions could enhance short-term and long-term developmental outcomes for young children with ASD.[2–6] Because of the potential to improve outcomes, increasing the proportion of all children who receive a developmental screening by age 36 months and the proportion of children with ASD who receive special services by age 48 months are included as Healthy People 2030 goals.[7]
Since 2010, CDC has conducted active population-based surveillance of ASD among children aged 4 years as a subset of the Autism and Developmental Disabilities Monitoring (ADDM) Network to better understand early identification of ASD in communities. Surveillance among children aged 4 years in 2016[8] indicated similar prevalence among children of different racial and ethnic groups, consistent with trends among children aged 8 years.[9] In addition, ASD identification measured by cumulative incidence of diagnosis by age 48 months was higher among children aged 4 years (born in 2012) compared with children aged 8 years (born in 2008), suggesting increased early identification of ASD among the younger cohort.[8] Cumulative incidence represents the number of children identified at or before each month of age divided by the total population and, unlike median age calculations, it reflects differences in prevalence and allows direct age-by-age comparison over time and between groups of children.[9,10]
For surveillance year 2018, ASD surveillance among children aged 4 years expanded from a subset to all ADDM Network sites. For this age group, sites ascertained children with characteristics meeting the ASD case definition as well as those who were suspected of having ASD by a qualified provider.
This report focuses on early identification of children with ASD and presents the estimated prevalence of ASD and suspected ASD among children aged 4 years, cumulative incidence of ASD identified by age 48 months, and characteristics of children aged 4 years with ASD and suspected ASD identified by ADDM Network sites in 2018. These data can be used to track trends and support efforts to ensure children with ASD are identified and receive necessary evidence-based interventions as early as possible.
