1. Median delays in achieving key developmental milestones varied between 0.7 and 19.7 months for children with autism compared to sibling controls.
2. Children who were male, had co-occurring intellectual disability, or were diagnosed at younger ages had significantly greater developmental delays.
Evidence Rating Level: 2 (Good)
Study Rundown: Autism is a common neurodevelopmental disorder associated with developmental delays, particularly social. Autism is often comorbid with other neurological diseases. This study aimed to use data from several large cohorts of children with autism to describe both the average ages at which subjects met developmental milestones and variation in timing based on comorbidities and other underlying factors. The study group included about 17,000 individuals with autism and a control group of more than 4,000 siblings without autism or intellectual disability (ID), reflecting four different cohorts. Compared to the sibling control group, median delays varied between 0.7 and 19.7 months for attaining different individual milestones. Male subjects and subjects with co-occurring intellectual disability had significantly larger and more varied delays in attaining milestones. Developmental delays were also significantly longer for children diagnosed at younger ages. The sibling controls came from only one of the four included cohorts, which limits interpretation of delays themselves as not all data had internal controls. However, this large study provides valuable quantitative characterization of developmental delays in autism. Prognostic information is important for families of children with newly diagnosed autism spectrum disorders, and further study on any effects of intervention on developmental delays would also provide key insight.
Relevant Reading: Early diagnosis of autism and impact on prognosis: A narrative review
In-Depth [retrospective cohort]: The four included cohorts were all multisite. The study sample was 80% male and had a mean age of 9 years old at the time of cross-sectional assessment; 38% had a co-occurring intellectual disability. Among about 5,000 subjects for whom exome sequencing data was available, 6.6% had rare variants associated with neurodevelopmental disorders. The studied developmental milestones were smiling, feeding self with a spoon, speaking words and phrases, bowel and bladder control, and gross motor skills such as sitting upright, crawling, and walking. 4.2% of subjects did not attain any of these milestones within the study period. Cohorts were compared using time-to-event distributions. Time-to-event distributions differed significantly between all cohorts. Children in the earliest cohort, which reflects data gathered starting in 1997, reached milestones later and had more variable delays than children in more recent cohorts.
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