Introduction

The first night effect (FNE) is the tendency to have lower than usual sleep quality and quantity during the first polysomnography (PSG) recording, which alters sleep architecture. The FNE occurs in autism spectrum disorder (ASD), with studies suggesting that cardiac autonomic dysregulation is altered in patients with this illness.

Objective

To determine whether the FNE influences the autonomic activity of ASD and typically developing (TD) children.

Method

Two PSGs were recorded in 13 ASD and 13 TD children. The FNE was evaluated with eight sleep variables and autonomic activity through respiratory sinus arrhythmia (RSA) and low frequency (LF). Statistical analyses included intra- and inter-subject comparisons.

Results

The FNE was present in both groups and affected more sleep variables in the ASD group. There were no significant differences between both recordings in RSA and LF. Inter-subject comparison showed significant differences in certain sleep variables, mainly during the first night. A comparison of RSA and LF between N2 and N3 stages and REM sleep showed that the TD group had significant differences in both measures whereas the ASD group only did so in the LF the first night.

Discussion and conclusion

The influence of the FNE on the quantitative characteristics of sleep is corroborated in ASD and TD children, but not in RSA or LF. When the activity of the RSA and LF between sleep stages was considered, a different pattern was observed between the two PSG recordings.

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