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Latent class analysis of early developmental trajectory in baby siblings of children with autism

Authors

  • Rebecca J. Landa,

    1. Center for Autism and Related Disorders, Kennedy Krieger Institute, Psychiatry and Behavioral Sciences, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
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  • Alden L. Gross,

    1. Mental Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
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  • Elizabeth A. Stuart,

    1. Mental Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
    2. Biostatistics, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, USA
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  • Margaret Bauman

    1. Lurie Center/LADDERS, Mass General Hospital for Children, Neurology, Harvard Medical School, Baltimore, MD, USA
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  • Conflicts of interest statement: No conflicts declared.

Abstract

Background:  Siblings of children with autism (sibs-A) are at increased genetic risk for autism spectrum disorders (ASD) and milder impairments. To elucidate diversity and contour of early developmental trajectories exhibited by sibs-A, regardless of diagnostic classification, latent class modeling was used.

Methods:  Sibs-A (= 204) were assessed with the Mullen Scales of Early Learning from age 6 to 36 months. Mullen T scores served as dependent variables. Outcome classifications at age 36 months included: ASD (= 52); non-ASD social/communication delay (broader autism phenotype; BAP; = 31); and unaffected (= 121). Child-specific patterns of performance were studied using latent class growth analysis. Latent class membership was then related to diagnostic outcome through estimation of within-class proportions of children assigned to each diagnostic classification.

Results:  A 4-class model was favored. Class 1 represented accelerated development and consisted of 25.7% of the sample, primarily unaffected children. Class 2 (40.0% of the sample), was characterized by normative development with above-average nonverbal cognitive outcome. Class 3 (22.3% of the sample) was characterized by receptive language, and gross and fine motor delay. Class 4 (12.0% of the sample), was characterized by widespread delayed skill acquisition, reflected by declining trajectories. Children with an outcome diagnosis of ASD were spread across Classes 2, 3, and 4.

Conclusions:  Results support a category of ASD that involves slowing in early non-social development. Receptive language and motor development is vulnerable to early delay in sibs-A with and without ASD outcomes. Non-ASD sibs-A are largely distributed across classes depicting average or accelerated development. Developmental trajectories of motor, language, and cognition appear independent of communication and social delays in non-ASD sibs-A.

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