To read the full paper by Abigail Chase, Lisa Hamrick, Holley Arnold, Jenna Smith, Rachel Hantman, Kaitlyn Cortez,Tatyana Adayev, Nicole D. Tortora, Alison Dahlman, and Jane Roberts, click 這裡. 

背景

The Fragile X Premutation (FXpm) is caused by a CGG repeat between 55-200 in the FMR1 gene and is linked with Autonomic Nervous System (ANS) dysfunction in adults. ANS activity can be measured using Respiratory Sinus Arrhythmia (RSA, a marker of parasympathetic regulation) and Interbeat Interval (IBI, the time between heartbeats influenced by both sympathetic and parasympathetic systems). This study is the first to investigate ANS function in infants with FXpm. The study investigates whether RSA and IBI differ in infants with FXpm compared to neurotypical infants and whether CGG repeats length relates to these measures. 

Eighty-two twelve-month-old infants (33 FXpm, 49 neurotypical) were assessed. Baseline ANS function was derived based on heart activity recordings followed by developmental assessments. The study found that RSA was significantly lower in FXpm infants compared to neurotypical infants, however IBI did not significantly differ. No significant relationship was found between CGG repeat length and either RSA or IBI. 

Why this research is important

The study makes several important contributions to understanding the relationship between RSA and FXpm infants. Lower RSA has been linked to difficulties with social and emotional regulation. These findings align with emerging evidence of sensory and social communication challenges in young children with FXpm and with high rates of anxiety, ADHD and autism seen in this population. While IBI did not differ at 12 months, previous work in Fragile X Syndrome suggests that changes may emerge later in development or may reflect distinct clinical features such as anxiety. It also suggests that early identification of reduced RSA in FXpm infants may help target children who could benefit from early support and intervention.  

This study included only 82 infants, so larger samples are needed to provide a fuller understanding of the relationship between FXpm and RSA. Within the FXpm group, it was found that RSA varied. This can be driven by numerous factors e.g. age, sex, CGG repeat length and environment, highlighting the need to explore mechanisms driving these differences. 

The authors call for future research that examines larger, more diverse samples, tracks developmental changes over time, and examines a broader range of genetic and molecular influences ANS function.