Features of atypical development, which may signal the broader autism phenotype (BAP), can be detected by the age of 1 year in siblings of children already diagnosed with autism spectrum disorder (ASD), new research suggests.
A study of 294 infants deemed high-risk for ASD because they had an older sibling with the disorder and 116 deemed low-risk showed that 28% of the high-risk group were classified as having "nontypical development" (non-TD) by the age of 36 months, and 17% were diagnosed with ASD.
In addition, the high-risk/non-TD group differed significantly from the low-risk group by the age of 12 months on measures of cognition, language, and social interaction.
"When we looked at this group, almost half of them had some sort of delays or differences in their development," lead author Sally Ozonoff, PhD, professor and vice-chair in the Department of Psychiatry and Behavioral Sciences at the MIND Institute at the University of California, Davis, Medical Center in Sacramento, told Medscape Medical News.
"That it was so high in these younger siblings was a bit of a surprise. We were also surprised that we could see this as early as the first birthday," she added.
The investigators note that the findings highlight the need for "close developmental surveillance" of this population, as well as for appropriate interventions to be implemented as needed.
"Having a child in the family with [ASD] means that subsequent infants born into the family should be regularly screened for developmental and behavioral problems by their pediatricians," said Dr. Ozonoff in a release.
The study was published online recently in the Journal of the American Academy of Child and Adolescent Psychiatry.
Largest Sample to Date
BAP "is a constellation of subclinical characteristics that are seen at elevated rates in family members of children with [ASD]," write the researchers.
They add that BAP commonly encompasses features of ASD, including language delays and social difficulties. "Most previous studies have examined the BAP in parents and school-age siblings of children with ASD; few have investigated BAP features in infancy and toddlerhood."
The investigators examined data from participants in their ongoing Infant-Sibling Study, including 294 infants who were categorized as high-risk for ASD, and 116 infants who were categorized as low-risk.
All participants underwent testing at 6, 12, 18, 24, and 36 months of age. When they were 3 years old, all of the children were classified as having either ASD, typical development (TD), or nontypical development (non-TD).
The non-TD group had high scores on the Autism Diagnostic Observation Schedule (ADOS) and/or low scores on 4 subscales of the Mullen Scales of Early Learning. The subscales measured fine motor function, visual reception, expressive language, and receptive language.
Other measures used included examiner-rated social engagement, such as frequency of eye contact and overall social responsiveness, and "clinical best estimate outcome classification" at the 36 -month mark.
"The current study is the largest sample to date that examines BAP features longitudinally," note the researchers.
Results showed that 51 of the children were classified as having ASD, including 17.4% of the high-risk group, at 36 months of age.
In addition, 83 were classified as having non-TD outcomes, not including ASD. This represented 28.2% of the high-risk group.
A total of 276 of the children were classified as having TD, with 160 high-risk TD and 116 low-risk TD.
Looking backward, all of the groups had comparable values at the age of 6 months on all 4 of the Mullen subscales. However, the high-risk non-TD group had lower rates of growth with age than did the TD groups.
In fact, by the age of 12 months, there were significant differences between the non-TD and low-risk TD groups on all scales except for fine motor function (P < .05 for the Mullen Expressive Language and Visual Reception scales, P < .001 for Mullen Receptive Language).
In addition, the non-TD group showed significant differences from the low-risk TD group in examiner-rated social engagement composite scores starting at the age of 12 months (P < .001).
The ADOS was first administered at the 18-month visit, and it also showed a significant difference on the social-communication algorithm score for the non-TD group vs the low-risk TD group (by 2.3 points; P < .001).
A total of 90% of the non-TD group showed ADOS-measured social-communication difficulties through reduced eye contact, repetitive vocalizations, delayed onset of gestures and speech, and extreme shyness with unfamiliar people.
"At 36 months, the 2 TD groups had comparable scores (1.5 and 1.9, respectively), whereas the Non-TD and ASD group showed significantly higher scores (estimated values 5.7 and 13.1, respectively)," report the investigators.
Early Interventions Needed
The non-TD group also had significantly higher rates of BAP, behavior problems, global developmental delay, and speech-language problems than the TD groups at the 36-month clinical judgement (P < .001 for all). In fact, one third of the non-TD group were classified as having BAP.
The investigators note that figuring out what types of interventions should be provided to these children is not always easy ― and that no single approach can fit a group with such a wide range of difficulties.
"Intervention approaches need to be chosen based on each child's profile of strengths and weaknesses and each family's goals and priorities. However, there are a range of choices available to early intervention professionals from a range of disciplines," they write.
"Good clinical practice suggests that when children are showing atypical development, they and their families should be provided with information about the child's difficulties, clinical reports when practical, and referrals to local service providers," said Dr. Ozonoff.
She said it was also important to note that the study population was not being diagnosed at the age of 12 months. Instead, they were being evaluated at that time for signs of developmental delays.
"They didn't go on to meet the criteria for autism or for other disorders. The non-TD group was not a diagnosed group. We were just noting that there were statistically apparent differences from the control group in their development as early as 12 months," she explained.
"I think that's another reason why identifying them early is really important. Maybe we could have fewer of the children develop autism and more of them go onto a different trajectory where they develop just mild, nondiagnosable versions of difficulties."
The investigators report that these children will continue to be followed as they approach school age to see whether their developmental difficulties persist or whether new ones emerge over time.
Dr. Ozonoff added that previous research has shown higher rates of learning disabilities, depression, and attention-deficit/hyperactivity disorder (ADHD) in siblings of children with ASD as they get older, but all of these conditions are not diagnosable at the age of 3 years.
So as they continue to follow the study sample, the researchers will identify which children go on to meet diagnostic criteria for these disorders and then look back to see whether the developmental differences identified in the current study were predictive of the conditions.
The study was funded by grants from the National Institute of Mental Health. The study authors have reported no relevant financial relationships.
J Am Acad Child Adolesc Psychiatry. Published online January 23, 2014. Abstract
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Cite this: Developmental Delays Detectable in High-risk 1-Year-Olds - Medscape - Mar 12, 2014.