Table 3.
Stratified results by intellectual disability status for differences in decile means and hazard ratios comparing age at first evaluation noting developmental concern and time from first evaluation to first autism spectrum disorder diagnosis by advanced maternal age at child birth among children identified with autism spectrum disorder by the Autism and Developmental Disabilities Monitoring Network, 2008, 2010, and 2012
| With ID (N=2332) | Without ID (N=4608) | Missing ID (N=1472) | ||||
|---|---|---|---|---|---|---|
| Age at first evaluation (months) | ||||||
| Estimate | 95% CI | Estimate | 95% CI | Estimate | 95% CI | |
|
|
||||||
| Unadjusted | ||||||
| Median change | ||||||
| 20th percentile | −2.00* | −0.34, −0.57 | −1.00 | −2.66, 0.66 | −1.00 | −3.60, 1.60 |
| 40th percentile | −2.00* | −3.46, −0.54 | −3.00* | −4.91, −1.09 | −2.00 | −4.80, 0.80 |
| 60th percentile | −3.00* | −5.56, −0.43 | −5.00* | −7.55, −2.45 | −5.00 | −8.59, −1.41 |
| 80th percentile | −5.00 | −8.34, 1.66 | −3.00* | −5.49, −0.51 | 0.00 | −5.73, 5.73 |
| Hazard ratio | 1.16* | 1.05, 1.29 | 1.14* | 1.06, 1.23 | 1.07 | 0.94, 1.22 |
| Adjusted | ||||||
| Median change | ||||||
| 20th percentile | −0.79 | −2.38, 0.80 | −0.77 | −1.72, 0.17 | −0.76 | −3.36, 1.83 |
| 40th percentile | −0.71 | −2.27, 0.85 | −0.65 | −2.36, 1.06 | 0.56 | −3.45, 4.57 |
| 60th percentile | −0.36 | −2.45, 1.72 | 0.29 | −2.36, 2.94 | 0.19 | −8.09, 8.47 |
| 80th percentile | 1.81 | −2.31, 5.93 | 2.25 | −0.75, 5.72 | −1.45 | −15.71, 12.82 |
| Hazard ratio | 0.96 | 0.85, 1.08 | 1.03 | 0.95, 1.12 | 0.99 | 0.85, 1.08 |
| Time from evaluation to diagnosis (months) | ||||||
| % Censored (AMA, non-AMA) | 20.91 | 26.30 | 32.51 | 34.69 | 24.46 | 26.17 |
| Unadjusted | ||||||
| Median change | ||||||
| 40th percentile | −1.00 | −2.13, 0.13 | −1.00 | −2.02, 0.02 | 0.00 | - |
| 60th percentile | −1.00 | −4.02, 2.02 | −3.00* | −5.37, −0.63 | 1.00 | −0.67, 2.67 |
| 80th percentile | 1.00 | −4.23, 6.23 | −2.00 | −6.00, 1.98 | 2.00 | −4.00, 8.00 |
| Hazard ratio | 1.13* | 1.00, 1.27 | 1.07 | 0.98, 1.17 | 1.02 | 0.88, 1.19 |
| Adjusted | ||||||
| Median change† | ||||||
| 40th percentile | 0.73 | 0.22, 1.22 | 0.63 | 0.31, 0.95 | 0.00 | - |
| 60th percentile | 2.23 | −2.00, 6.46 | 1.6.0 | −0.54, 3.73 | −1.19 | −8.52, 6.13 |
| 80th percentile | 0.77 | −13.88, 15.43 | 1.41 | −5.59, 8.41 | 0.42 | −1.95, 2.79 |
| Hazard ratio | 1.03 | 0.90, 1.18 | 1.03 | 0.93, 1.14 | 0.97 | 0.81, 1.16 |
Advanced maternal age defined as childbirth at ≥35 years of age
ID Intellectual disability, defined as IQ test score ≤70 or indication of ID on the child’s record
Sample subset to sites that collected ID data for >60% of children (Alabama, Arkansas, Arizona, Colorado, Georgia, Maryland, North Carolina, New Jersey, South Carolina, and Utah)
Adjusted model controlled for maternal race/ethnicity, maternal education, study site, child year of birth, child gestational age, paternal age, parity, birth order, and record type with multiple imputation to account for missing paternal age data
Statistically significant at an alpha=0.05 level
Deciles 10–30 not shown due to time difference being 0 for all observations in those deciles