Dynamic cerebral autoregulation in healthy males during sleep accompanied by intermittent hypoxia

Obstructive sleep apnea is an independent risk factor for stroke, potentially due to intermittent hypoxia (IH)-induced impairment of cerebral autoregulation. Human cerebral autoregulation during sleep is poorly characterized, and whether IH exposure during sleep alters cerebral autoregulation during sleep is unknown. In a secondary, exploratory analysis of previously collected cerebral blood flow (transcranial Doppler ultrasound measurement of peak blood velocity through the middle cerebral artery; [Formula: see text]), mean arterial pressure (MAP; finger photoplethysmography), and end-tidal partial pressure of CO₂ ([Formula: see text]) data, dynamic cerebral autoregulation (dCA) was quantified using transfer function analysis gain, phase, and coherence in healthy males (<i>n</i> = 10; age: 26 ± 6 yr; body mass index: 24.5 ± 1.7 kg/m²; MAP: 87.5 ± 8.0 mmHg) during wakefulness and during nonrapid eye movement (NREM) sleep in normoxia or accompanied by IH. Compared with wakefulness, [Formula: see text] variability was lower during both sleep in normoxia and sleep accompanied by IH in the very low frequency (0.02-0.07 Hz) and low frequency (LF: 0.07-0.2 Hz) ranges (both comparisons, <i>P</i> ≤ 0.02) with MAP variability being lower in the LF range (<i>P</i> = 0.045); gain, phase, and coherence were similar between wakefulness and sleep (all comparisons, <i>P</i> ≥ 0.062). dCA measures during normoxic and IH-sleep were similar (all comparisons, <i>P</i> ≥ 0.09). Moreover, dCA gain and phase, and multiple and partial coherences during IH-sleep were not different between acute (<1 h) and prolonged (∼2 h) exposure (all comparisons, <i>P</i> ≥ 0.055) even though [Formula: see text] was lower following prolonged IH exposure (<i>P</i> = 0.002). These findings indicate dCA is effective during stage 2/3 NREM sleep and is not impacted by ∼2 h of sleep accompanied by IH.<b>NEW & NOTEWORTHY</b> This study found that dynamic cerebral autoregulation (dCA) is not different between wakefulness and stages 2/3 nonrapid eye movement (NREM) sleep in young healthy males and that ∼2 h of intermittent hypoxia exposure during sleep mimicking that experienced by patients with moderate-to-severe obstructive sleep apnea does not alter NREM stage 2/3 sleep dCA. This maintained dCA during sleep may result from the reduced cerebral blood flow and blood pressure variability observed during sleep.