Arousal Responses during Overnight Polysomnography and their Reproducibility in Healthy Young Adults

STUDY OBJECTIVES: Arousal intensity and heart rate (HR) response to arousal during polysomnography (PSG) vary considerably between patients with sleep disorders. Our objective was to determine the range of these arousal characteristics in healthy young adults and whether they are consistent on repeated testing. DESIGN: Post hoc analysis of 56 preexisting PSG files recorded from 28 healthy adults on 2 consecutive nights. SETTING: Academic medical center and Research and Development Laboratory (YRT Limited, Winnipeg, Manitoba, Canada). PARTICIPANTS: Twenty-eight healthy young adults. INTERVENTIONS: None. MEASUREMENTS AND RESULTS: Arousals were identified using an automatic system followed by manual editing. The intensity of arousals was scaled (between 0 and 9) using an automatic algorithm based on the change in the electroencephalography (EEG) signals' wavelet characteristics. 4,751 arousals in 28 pairs of PSGs (night 1 and night 2) were scaled. HR responses (ΔHR) to all arousals were determined and averaged at each arousal scale per file. Overall average arousal intensity ranged 3.0-7.1 in different subjects, and average ΔHR ranged 1.9-18.3 beats.min(-1). Heart rate response at a given arousal intensity, expressed as ΔHR at a moderate arousal scale of 5.0 (ΔHR5), ranged 4.1-18.1 beats.min(-1). There was a strong correlation between arousal intensity and ΔHR within each subject. More importantly, there were excellent intraclass correlations (ICC) between night 1 and night 2 results for all three variables (ICC = 0.72 for average intensity, 0.92 for average ΔHR4, and 0.91 for ΔHR5). CONCLUSIONS: Average arousal intensity and heart rate response to arousal are highly variable among healthy young adults and stable within individuals.