Materials and Methods
Ethical approval was provided by the ethical review board of China Medical University Hospital (CMUH103-REC2-082). Patient consent was not required for this research. The data for children (< 18 years old) with sleep problems who came to the outpatient department (OPD) of China Medical University Children’s Hospital for help and underwent PSG from April 2015 to May 2017 were collected and analyzed retrospectively. However, data for those who underwent follow-up PSG studies after adenotonsillectomy or for other reasons were excluded in this study.
The indications for PSG include snoring, sleep apnea, other sleep-related breathing disorders, excessive daytime sleepiness, limb movements while sleeping, bruxism, enuresis, sleep walking, insomnia, difficulty falling sleeping, and others.
A level 1 PSG study is performed in our sleep laboratory with a sleep technologist present, and 12 channels are recorded, including eight channels of electroencephalography (EEG), 2 channels of electrooculography (EOG), 1 channel of submentalis (chin) electromyography (EMG), and 1 channel of electrocardiogram (ECG)/heart rate, and 1 channel of pulse oximetry (SpO2). A multiple sleep latency test (MSLT) was also arranged for the day after any PSG study for those children who had a history of more than 3 months of excessive daytime sleepiness.
Obstructive sleep apnea syndrome (OSAS) was diagnosed based on the PSG data when obstructive events were noted and the apnea-hypopnea index (AHI) was one or more per hour, with 1< AHI ≤5 taken to indicate mild OSA, 5< AHI ≤10 taken to indicate moderate OSAS, and an AHI >10/hr of total sleep time (TST) taken to indicate severe OSAS.
The periodic limb movements (PLMs) during sleep were scored if there were at least four movements of 0.5–5/sec’ duration that occurred between 5 and 90s apart. A PLM index of >5 per hour of sleep is generally considered to be rare in normal children, and therefore this threshold was used to define the presence of periodic limb movement disorder (PLMD).
Central sleep apnea (CSA) was defined as the absence of both inspiratory effort and chest wall movement lasting longer than 20 seconds when accompanied by a central apnea index greater than 1.
Furthermore, the presence of two or more sleep-onset rapid eye movement (REM) periods (SOREMPs) and a mean sleep latency of <8 minutes on the MSLT was regarded as being diagnostic of narcolepsy.