Factors Affecting Age at Initial Autism Spectrum Disorder Diagnosis in a National Survey
Table 3
Multivariate random-effects linear regression model (clustering by state) of log-transformed age at initial ASD diagnosis (AOD), adjusted by age and age of concern ().
Parameter
Raw coefficient
Average difference in AOD compared with reference group (in mo)*
95% CI Difference (in mo)
P
Gender
Male
REF
Female
0.04
0.46
0.06
0.87
< .025
Race
White
REF
African-American
0.08
1.08
0.1
2.12
.031
Multiracial
0.10
1.45
0.62
2.33
< .001
Other
0.06
0.82
0.07
1.6
.032
Ethnicity
Hispanic
−0.02
−.16
−0.73
0.44
—
Not Hispanic
REF
Initial ASD Diagnosis
Autism
REF
PDD-NOSa
0.09
1.32
0.92
1.72
< .001
Asperger
0.62
12.39
11.49
13.32
< .001
Other ASD
0.08
1.16
0.67
1.66
< .001
Intellectual disability
b (ID)
Present
−0.05
−0.67
−1.04
−0.28
< .001
Absent
REF
Firstborn
0.03
0.36
0.05
0.67
.024
Not firstborn
REF
History of autistic regression
−0.08
−1.05
−1.38
−0.72
< .001
No regression
REF
Maternal education
≤College diploma
REF
College diploma
−0.02
−0.27
−0.42
−0.12
< .001
County median income
Lowest quartile
REF
2nd quartile
0.1
1.55
0.43
2.76
.006
3rd quartile
0.08
1.07
0.06
2.15
.038
4th quartile
0.05
0.63
−0.35
1.67
—
County percent white
Lowest quartile
REF
2nd quartile
0.02
0.20
−0.18
0.58
—
3rd quartile
0.05
0.63
0.14
1.13
.012
4th quartile
0.05
0.66
−0.08
1.43
—
Rurality
Metropolitan/peri-metro
REF
Large/small town/rural
0.05
0.74
0.37
1.12
< .001
Region
Northeast
REF
South
0.11
1.69
1.23
2.16
< .001
Midwest
0.11
1.65
1.18
2.13
< .001
West
0.1
1.46
0.95
1.99
< .001
Adjusted by current age and log age of concern (AOC). Note—: P > .05, statistical nonsignificance.
aPDD-NOS: Pervasive Developmental Disorder-Not Otherwise Specified.
bID: Intellectual disability/mental retardation.
cHigh risk: history of prematurity and/or seizures and/or cerebral palsy.
