Factors Affecting Age at Initial Autism Spectrum Disorder Diagnosis in a National Survey
Table 1
Comparison of mean age of first concern (AOC) and age of first diagnosis (AOD) by characteristic (); univariate testing by ANOVA on log-transformed AOC and AOD.
Characteristic
Mean age at first concern (AOC), mo. (SD)*
ANOVA value/median
Mean age at first diagnosis (AOD), mo. (SD)*
ANOVA value/median
Overall
6214
19.6 (15.0)
47.6 (30.8)
Median
18 (IQR 11,24)
36.9 (IQR 27.8, 56.4)
Gender
< .001
.796
Male
5119
19.8
47.6
Female
1095
18.6
49.0
Race
.048
.367
White
5491
19.5
47.8
African-American
165
21.7
49.2
Asian/Asian-American
57
21.7
45.8
Multiracial
244
18.7
50.0
Other/unknown
257
19.6
46.4
Ethnicity
< .05
.004
Hispanic
5709
19.9
44.0
Not Hispanic
505
19.5
48.2
Current age, years*
< .001
< .001
0–5
940
14.4
29.0
6–11
3692
18.7
42.4
12–18
1582
24.7
71.9
Initial ASD Diagnosis
< .001
< .001
Autism
2535
10.5
38.3
PDD-NOSa
1893
13.5
44.9
Asperger
891
24.4
87.8
Other ASD
895
11.9
41.7
Intellectual disability
b (ID)
< .001
.194
Present
1229
17.8
48.3
Absent
4971
20.0
47.8
Firstborn
3242
20.6
< .001
49.1
< .001
Not firstborn
2971
18.5
46.5
History of autistic regression
1511
16.9
.854
38.2
< .001
No regression
4703
20.4
51.0
High-risk
c
< .001
.535
Yes
650
16.0
47.4
No
5563
20.0
47.9
Multiplex family
.255
.776
Yes
872
21.0
49.4
No
5342
19.3
47.6
Era of Initial Diagnosis
.601
< .001
1994–2000
850
18.5
39.3
2001–2008
5364
19.7
49.2
Maternal education
.468
.007
≤College diploma
3098
19.5
48.9
College+
3116
19.6
46.8
County median income
.537
< .001
Lowest quartile
171
14.9
46.6
2nd quartile
486
14.9
47.2
3rd quartile
1211
16.3
51.1
4th quartile
4344
14.7
49.9
County percent white
.494
< .001
Lowest quartile
2206
19.3
46.6
2nd quartile
2453
19.4
47.2
3rd quartile
1178
20.6
51.0
4th quartile
375
19.4
49.9
Rurality 50
.595
< .001
Large central metro
1364
19.6
45.1
Large fringe metro
2104
19.2
46.0
Medium metro
1303
19.3
48.5
Small metro
644
20.8
53.6
Micropolitan
538
20.5
51.2
Noncore (rural)
261
18.2
52.2
Binary rural
.621
< .001
Principal city ≥ 1 million
368
19.4
45.7
Principal city < 1 million
2746
19.8
50.6
US Region
.311
< .001
Northeast
1843
18.9
44.8
South
1808
19.4
50.1
Midwest
1434
20.5
49.8
West
1129
19.6
46.7
Note -: not significant. Some totals in categories do not add up to 6214 due to missing data.
aPDD-NOS: Pervasive Developmental Disorder-Not Otherwise Specified.
bID: Intellectual disability/mental retardation.
cHigh risk: history of prematurity (<34 weeks gestational age) and/or seizures and/or cerebral palsy; sibling with ASD not included.