Table 2. Variance Components, Heritability Estimates, and Goodness-of-Fit Model for the Probability of Autism Spectrum Disordera.
| Model No.b | Random-effects model and model fit, fix model (No.) | −2× Likelihood | AIC (difference to above model)c | Heritability (h2) estimates (95% CI) | |||
|---|---|---|---|---|---|---|---|
| Overall | Male | Female | Difference male vs female | ||||
| 1 | Sex | –158 639.20 | 158 647.20 (∆ = 0) | 0.872 (0.696 to 0.910) | NA | NA | NA |
| 2 | As model 1 | −158 633.53 | 158 645.54 (∆ = −1.66) | NA | 0.894 (0.690 to 0.977) | 0.786 (0.599 to 0.874) | 0.108 (−0.082 to 0.262) |
| 3 | Sex + birth year + (sex × birth year) | −152 991.52 | 153 015.52 (∆ = −5630.02) | 0.832 (0.793 to 0.869) | NA | NA | NA |
| 4 | As model 3 | −152 987.10 | 153 015.10 (∆ = −0.42) | NA | 0.875 (0.670 to 0.931) | 0.765 (0.690 to 0.837) | 0.110 (0.008 to 0.215) |
| 5 | Sex + birth year + paternal age + maternal age + (sex × birth year) + (sex × paternal age) + (sex × maternal age) | −152 779.58 | 152 819.58 (∆ = −195.52) | 0.826 (0.787 to 0.864) | NA | NA | NA |
| 6 | As model 5 | −152 775.06 | 152 819.06 (∆ = −0.52) | NA | 0.870 (0.814 to 0.926) | 0.757 (0.684 to 0.831) | 0.113 (0.010 to 0.216) |
| 7 | As model 5 but alternative categorization of parental age | −152 901.87 | 152 941.87 (∆ = 122.81) | 0.828 (0.789 to 0.865) | NA | NA | NA |
| 8 | As model 7 | −152 897.47 | 152 941.47 (∆ = −0.40) | NA | 0.871 (0.815 to 0.926) | 0.760 (0.686 to 0.833) | 0.111 (0.007 to 0.214) |
| 9 | Sex + birth year + paternal age + maternal age + gestational age + (sex × birth year) + (sex × paternal age) + (sex × maternal age) + (sex × gestational age) | −152 392.95 | 152 440.95 (NA) | 0.825 (0.786 to 0.863) | NA | NA | NA |
| 10 | As model 9 | −152 388.39 | 152 440.39 (NA) | NA | 0.869 (0.813 to 0.924) | 0.757 (0.682 to 0.829) | 0.112 (0.010 to 0.216) |
Abbreviations: AIC, Akaike information criterion; NA, not applicable.
All individuals were followed for autism spectrum disorder diagnosis up to age 19 years.
All models include 1 047 649 individuals (538 283 male and 509 366 female individuals) with a total of 12 226 cases of autism spectrum disorder (8128 male and 4098 female). All models additionally include variance terms reflecting any shared childhood environmental effect (sex specific in models 2, 4, 6, 8, and 10) being essentially 0 and not shown. The following variables were categorized into quintiles: birth year (1985-1987, 1987-1990, 1990-1992, 1992-1995, and 1995-1998), maternal and paternal age (≤25 years, 26-30 years, and >30 years), and gestational age (<37 weeks, 37-38 weeks, and >38 weeks). Models 1, 3, and 5 include shared variance terms and models 2, 4, and 6 include sex-specific variances for additive genetic effects and childhood shared environment. Models 7 and 8 had different maternal age groups (<32 years, 32-37 years, and >37 years) and paternal age groups (<35 years, 35-42 years, and >42 years).
The AIC and log likelihood cannot be compared between models 9 and 10 and models 1 and 8 because 1632 individuals with unknown gestational age were dropped. The difference in AIC is therefore deliberately omitted.