Development of Respiratory Sinus Arrhythmia in Young Infants With Autism Spectrum Disorder, Preterm Birth, and Typical Development.

Researchers studied heart rate patterns in 137 babies from 1-24 months old, including those at higher risk for autism. They found that babies later diagnosed with autism showed different heart rate patterns from 9 months onwards, with more regulated patterns during rest periods. This might reflect how their nervous systems develop differently and could help with earlier identification of autism in the future.

This longitudinal study tracked respiratory sinus arrhythmia (RSA), a measure of nervous system function, in 137 infants from 1 to 24 months. Researchers followed infants at varying autism risk levels, including siblings of autistic children and preterm births, to understand early autonomic development patterns. While all infants showed normal RSA development in the first year, those later diagnosed with autism displayed elevated RSA from 9-24 months, contrasting with typically developing peers. Preterm infants initially showed lower RSA but normalized when corrected for gestational age.

These findings suggest potential early physiological differences in autism development and highlight the complexity of autonomic nervous system maturation in early childhood.

Results suggest RSA measurement from 9 months may aid early autism identification, though findings contradict previous research showing lower RSA in older autistic children. Clinical application requires validation through larger studies with clearer methodology.

Study design not specified in abstract. Unclear sample characteristics, diagnostic criteria, or methodology details. Findings may not generalize broadly without additional validation studies.

Respiratory sinus arrhythmia (RSA) is a key index of parasympathetic function and environmental adaptability. Lower resting RSA has been linked to preterm (PT) birth in infancy and autism spectrum disorder (ASD) in childhood, yet RSA across the first 2 years in young infants born PT or later diagnosed with ASD remains unknown. This study examined resting RSA and mean interbeat interval (IBI) development from 1 to 24 months in infants at varying ASD likelihoods, including infant siblings of children with ASD and those born PT. A longitudinal design tracked resting RSA and mean IBI in 137 infants from 1 to 24 months.

Infants were classified as elevated likelihood for ASD (EL), low likelihood for ASD (LL), or PT and later classified by developmental outcome as ASD, neurodivergent (ND), or typically developing (TD). Mixed-effects models examined developmental trajectories and group differences. Results indicated that both RSA and mean IBI increased across all groups from 1 to 24 months, with the most rapid growth observed in the first 6 months. PT infants exhibited lower RSA and mean IBI initially, but aligned with LL infants when age was corrected for prematurity.

Infants later diagnosed with ASD showed no early RSA differences, but exhibited elevated RSA from 9 to 24 months, distinguishing them from TD and ND infants. Elevated resting RSA in ASD from 9 to 24 months may reflect reduced social monitoring, increased attentional regulation, or decreased stress during a resting period free of structured tasks. These findings contrast with lower RSA in older children with ASD, highlighting developmental shifts in autonomic function and the need for further research into RSA as an early biomarker for ASD.