Prevalent hypertension and stroke in the Sleep Heart Health Study: association with an ECG-derived spectrographic marker of cardiopulmonary coupling.

STUDY OBJECTIVES: The electrocardiogram (ECG)-based sleep spectrogram generates a map of cardiopulmonary coupling based on heart rate variability and respiration derived from QRS amplitude variations. A distinct spectrographic phenotype, designated as narrow-band elevated low frequency coupling (e-LFC(NB)), has been associated with central apneas and periodic breathing and predicts sleep laboratory failure of continuous positive airway pressure therapy. This study assesses, at a population level, the associations of this spectrographic biomarker with prevalent cardiovascular disease using the Sleep Heart Health Study (SHHS)-I dataset. DESIGN: Retrospective analysis of the Sleep Heart Health Study-I dataset. SETTING: Laboratory for complex physiologic signals analysis. MEASUREMENTS AND RESULTS: The fully-automated ECG-derived sleep spectrogram technique was applied to 5247 (of the original 6441) polysomnograms from the SHHS-I. Associations were estimated with use of various drugs and pathologies including prevalent hypertension and cardiovascular and cerebrovascular disease. Increasing with age and more common in males, e-LFC(NB) is also associated with greater severity of sleep apnea and fragmented sleep. After adjustment for potential confounders, an independent association with prevalent hypertension and stroke was found. CONCLUSIONS: An ECG-derived spectrographic marker related to low frequency cardiopulmonary coupling is associated with greater sleep apnea severity. Whether this biomarker is solely a sign of more severe disease or whether it reflects primary alterations in sleep apnea pathophysiology (which may either cause or result from sleep apnea) is unknown. This ECG-based spectral marker is associated with a higher prevalence of hypertension and stroke.

A pilot study of sleep, cognition, and respiration under 4 weeks of intermittent nocturnal hypoxia in adult humans.

STUDY OBJECTIVES: A pilot study to examine the effects of intermittent nocturnal hypoxia on sleep, respiration and cognition in healthy adult humans. METHODS: Participants were eight healthy, non-smoking subjects (four male, four female), mean age of 26.4+/-5.2 years, and BMI 22.3+/-2.6 kg/m(2), exposed to 9h of intermittent hypoxia between the hours of 10 P.M. and 7 A.M. for 28 consecutive nights. At a simulated altitude of 13,000 feet (FIO(2) 0.13), intermittent hypoxia was achieved by administering nasal nitrogen, alternating with brief (approximately 5s) boluses of nasal oxygen. Pre- and post-exposure assessments included polysomnography, attention (20-min Psychomotor Vigilance Test), working memory (10-min verbal 2 and 3-back), Multiple Sleep Latency Test, and the Rey Auditory Verbal Learning Test. Obstructive and non-obstructive respiratory events were scored. RESULTS: Overall sleep quality showed worsening trends but no statistically significant change following exposure. There was no difference after hypoxia in sleepiness, encoding, attention or working memory. Hyperoxic central apneas and post-hyperoxic respiratory instability were noted as special features of disturbed respiratory control induced by intermittent nocturnal hypoxia. CONCLUSIONS: In this model, exposure to nocturnal intermittent hypoxia for 4 weeks caused no significant deficits in subjective or objective alertness, vigilance, or working memory.