Beta intrusion during N2 sleep is negatively associated with nocturnal heart rate variability in healthy adults

Abstract

Increased cognitive hyperarousal is a proposed mechanism associated with clinical poor sleep including insomnia. An objective marker of nocturnal hyperarousal is high frequency electroencephalography during sleep, including increased beta frequency during stage two (N2) sleep. Acute and chronic poor sleep quality are associated with autonomic dysfunction, but little is known regarding the relationship between nocturnal beta frequency intrusion and nocturnal autonomic function. The purpose of this study was to explore the association between beta spectral power during stage two (N2) sleep and nocturnal heart rate variability (HRV) in healthy female and male adults. We hypothesized that heightened beta spectral power during N2 sleep would be associated with reduced nocturnal HRV. Twenty-four participants (12 males, 12 females; age, 25 ± 1 years; BMI 27 ± 1 kg/m2) underwent an 8-hour overnight sleep opportunity with continuous polysomnography and 5-lead electrocardiogram monitoring. Periods of 5 – 10 minutes of stable N2 sleep absent of cortical arousals, respiratory events, and limb movement-associated arousals were identified (one per cycle) for analysis. Periods from the first two cycles of N2 sleep from the full night were selected for analysis. Beta spectral power from the central and frontal regions and nocturnal HRV data were analyzed and averaged across each hemisphere. Time-domain HRV was quantified as the root mean squared of successive differences (RMSSD) and proportion of R-R intervals (RRI) varying by greater than 50 ms (pNN50). An inverse correlation was observed between central beta power and RRI (R= -0.473, p=0.019), pNN50 (R= -0.450, p=0.028), and RMSSD (R= -0.406, p=0.049). This was paralleled by a similar relationship between frontal beta and RRI (R= -0.487, p=0.016) and pNN50 (R= -0.423, p=0.039). Our results indicate a negative association between N2 beta power and nocturnal HRV measures. These findings suggest that nocturnal hyperarousal may be associated with poor cardiac autonomic function and has implications for individuals with insomnia in whom cognitive hyperarousal is frequently reported. Support is provided by the National Institutes of Health (AA-024892, U54GM115371; P20GM103474, 2TL1 TR002318). This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.