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Table 3 Results of standard linear mixed-effects models for different age groups within the sample

From: Atypical development of white matter microstructure of the corpus callosum in males with autism: a longitudinal investigation

  Intercept Group P -value Age P -value Age X Group P -value
Genu FA
<10 years old 0.73 −0.22a <0.001 0.010 0.03 −0.0189 0.002
10 to 20 years old 0.63 −0.02 0.04 0.001 0.48 0.0002 0.89
>20 years old 0.65 −0.04 0.004 −0.003 0.004 0.0019 0.09
Body FA
<10 years old 0.69 −0.15 0.003 0.009 0.02 −0.0129 0.008
10 to 20 years old 0.64 −0.02 0.01 0.005 <0.001 −0.0019 0.12
>20 years old 0.65 −0.03 0.03 −0.002 0.03 0.0009 0.45
Splenium FA
<10 years old 0.77 −0.15 0.006 0.008 0.06 −0.0110 0.03
10 to 20 years old 0.71 −0.01 0.11 0.002 0.01 0.0001 0.94
>20 years old 0.72 −0.02 0.01 −0.001 0.23 0.0010 0.26
Genu MD
<10 years old 0.66 0.15 0.008 −0.011 0.02 0.0130 0.02
10 to 20 years old 0.75 0.01 0.22 −0.001 0.19 −0.0002 0.85
>20 years old 0.72 0.02 0.07 0.002 0.008 −0.0008 0.41
Body MD
<10 years old 0.76 0.08 0.12 −0.006 0.14 0.0050 0.30
10 to 20 years old 0.78 0.01 0.24 −0.003 0.007 −0.0004 0.75
>20 years old 0.76 0.02 0.12 0.001 0.19 −0.0004 0.74
Splenium MD
<10 years old 0.75 0.07 0.30 −0.003 0.57 0.0028 0.63
10 to 20 years old 0.77 0.01 0.40 −0.001 0.28 0.0004 0.73
>20 years old 0.74 0.02 0.048 0.002 0.01 −0.0011 0.28
Genu RD
<10 years old 0.23 0.28 0.001 −0.014 0.04 0.0236 0.005
10 to 20 years old 0.37 0.02 0.10 −0.001 0.34 −0.0005 0.74
>20 years old 0.32 0.04 0.009 0.004 0.004 −0.0020 0.15
Body RD
<10 years old 0.34 0.14 0.006 −0.010 0.02 0.0115 0.02
10 to 20 years old 0.38 0.02 0.03 −0.005 <0.001 0.0009 0.48
>20 years old 0.35 0.03 0.03 0.003 0.02 −0.0009 0.48
Splenium RD
<10 years old 0.26 0.17 0.01 −0.006 0.22 0.0113 0.08
10 to 20 years old 0.30 0.01 0.10 −0.002 0.049 −0.0001 0.92
>20 years old 0.28 0.03 0.007 0.002 0.04 −0.0013 0.26
Genu AD
<10 years old 1.35 −0.03 0.68 −0.008 0.12 −0.0019 0.75
10 to 20 years old 1.40 −0.01 0.20 −0.001 0.41 −0.0012 0.54
>20 years old 1.36 −0.01 0.66 0.000 0.76 0.0005 0.70
Body AD
<10 years old 1.47 0.03 0.73 −0.004 0.54 −0.0012 0.87
10 to 20 years old 1.51 −0.03 0.02 0.003 0.15 −0.0054 0.02
>20 years old 1.49 −0.02 0.30 −0.002 0.15 0.0014 0.41
Splenium AD
<10 years old 1.61 −0.07 0.30 0.007 0.18 −0.0091 0.17
10 to 20 years old 1.56 −0.01 0.33 0.001 0.51 −0.0003 0.86
>20 years old 1.53 0.01 0.56 0.001 0.71 −0.0003 0.87
  1. Age groups were defined as less than 10 years old, 10 to 20 years old, and greater than 20 years old. The analyses in those under 10 years of age included 34 individuals with ASD (48 scans) and 12 individuals with typical development (17 scans). The analyses in those between 10 and 20 years of age included 61 individuals with ASD (127 scans) and 34 individuals with typical development (67 scans). The analyses in those over 20 years of age included 46 individuals with ASD (112 scans) and 29 individuals with typical development (63 scans). The mixed effects models examined diagnostic group main effects (ASD versus typical development), age main effects, and age-by-group interactions for FA, MD, RD, and AD of the genu, body, and splenium of the corpus callosum. The mixed effect model was denoted as DTI metric ~ 1 + group + age (years) + group × Age + (1 | participant), while controlling for head motion, SNR, and head coil. All intercepts were statistically significant. aWhile this group effect is negative, caution should be employed when interpreting the direction of main effects in the presence of significant interactions. Graphically, the data demonstrate that most of the children under the age of 10 in the ASD group have higher levels of FA than in the typically developing group.