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Alpha Intrusion during Rapid Eye Movement (REM) Sleep Increases Blood Pressure

Rapid eye movement (REM) sleep is characterized by low voltage, mixed frequency electroencephalography (EEG). A hallmark of REM sleep includes episodic increases of blood pressure and heart rate, and a higher incidence of adverse cardiovascular events such as myocardial infarction and stroke. In pathological conditions such as fibromyalgia and other chronic pain conditions, alpha frequencies (8–13 Hz) are often observed during normal EEG frequencies, a phenomena referred to as alpha intrusion. The impact of alpha intrusion on blood pressure during REM sleep remains unknown. The purpose of this study was to utilize finger plethysmography to determine the impact of alpha intrusion on beat‐to‐beat blood pressure and heart rate during REM sleep. Eleven participants (6 female, 22±1 years, 28±1 kg/m2) were equipped with overnight finger plethysmography (NOVA, Finapres) and standard 10–20 EEG electrode placement for quantification of sleep stage (SleepWorks, Natus). Overnight EEG was scored according to the American Academy of Sleep Medicine (AASM) guidelines by a trained sleep technician and board‐certified sleep physician. EEG signals were filtered with a common low pass (35 Hz), high pass (0.5 Hz), and notch (60 Hz) filter. Occipital EEG was analyzed using an original MATLAB® code, applying a short‐term Fourier transform function (i.e., spectral analysis) with sliding window parameters of 10 seconds by 5 seconds. Alpha frequencies were normalized to the entire overnight EEG to quantify alpha power density. During the final REM episode, a representative 30 second sample of maximum alpha intrusion was selected, and compared to 30 second baseline and recovery periods immediately preceding and following the maximum alpha intrusion. Each EEG sample was free of any scorable arousals, apneic events, or significant limb movements. Continuous recordings of systolic arterial pressure (SAP), diastolic arterial pressure (DAP), and heart rate (HR) were analyzed during these timeframes. Statistical analysis included repeated measures ANOVA (p<0.05). Alpha power density increased during alpha intrusion (0.228 ± 0.02 μV to 0.347 ± 0.04 μV; p<0.001), and returned to baseline levels during recovery (0.205±0.03 μV). Similarly, SAP increased during alpha intrusion (121 ± 5 mmHg to 124 ± 5 mmHg; p=0.038), and returned to baseline during recovery (121 ± 6 mmHg). DAP tended to increase during alpha intrusion (p = 0.08), while HR did not change with alpha intrusion. These results suggest alpha intrusion increases REM blood pressure. These findings have potential clinical relevance given the higher incidence of adverse cardiovascular events during early morning REM sleep.