Reciprocal interactions between spontaneous and respiratory arousals in adults with suspected sleep-disordered breathing

Background and purpose: Excessive daytime sleepiness (EDS) is a major consequence of sleep-disordered breathing (SDB) in adults. In snoring children, spontaneous and respiratory arousals display reciprocal interactions, allowing for development of a new quantitative measure, the sleep pressure score (SPS), which provides intra-polysomnographic estimates of sleep pressure/disruption. The aim of the present study was to assess the interactions between respiratory and spontaneous arousals in adults with suspected SDB, and to examine whether the SPS and the Epworth sleepiness scale (ESS) are correlated. Patients and methods: Retrospective chart review of 530 adult patients who underwent polysomnographic evaluation for suspected SDB in two medical centers was performed. Polysomnographic studies reports, patients' demographics and ESS scores were reviewed. Results: Spontaneous and respiratory arousal indices and the apnea-hypopnea index (AHI) displayed negative and positive correlations respectively (r=-0.25, r=0.97, P<0.0001) indicating reciprocal interactions between respiratory and spontaneous arousals during sleep. The AHI corresponding to the SPS at which the respiratory arousal/total arousal fraction exceeded the spontaneous arousal/total arousal fraction occurred at approximately 14/h of total sleep time (TST) (compared to 7/h TST in children) (P<0.001). No correlation was found between SPS values and ESS scores. Conclusions: As in children, snoring adults exhibit reciprocal interactions between respiratory and spontaneous arousals that can also be expressed as a single quantitative measure, the SPS, which is highly dependent on the severity of SDB and could possibly serve as a more reliable index of sleep disruption, considering that the ESS is unrelated to either SPS or AHI.