The acute effects of a single session of intermittent hypoxia on blood biomarker concentrations and sleep parameters in people with Parkinson's disease: A randomized, double-blind, crossover trial.

BACKGROUND: People with Parkinson's disease (pwPD) exhibit sleep and blood biomarker alterations. Intermittent normobaric hypoxia (IH) may promote neuroprotection, but acute effects remain unclear. We aimed to investigate the acute and 24-h retention effects of a single session of IH on sleep parameters and blood biomarkers in pwPD. METHODS: Fifteen pwPD and 15 sex-matched neurologically healthy individuals participated in a randomized, double-blind, crossover study. Participants underwent two 39-min conditions: (i) IH, consisting of four 6-min hypoxic cycles (FiO2 = 0.10) interspersed with three 5-min normoxic periods; and (ii) normoxia protocol with constant oxygen availability (FiO2 = 0.21). Actigraphy-based sleep metrics and biomarkers (BDNF, cortisol, IL-6, iron, leptin, and adiponectin) were assessed at baseline, immediately post-session, and at 24-h after follow-up. RESULTS: IH reduced SpO2 (5-20%) and increased hypoxic dose of nearly five times versus normoxia, confirming successful simulation. No effects on sleep parameters were observed post-IH versus baseline in either group. In pwPD, total sleep time decreased 24-h after IH versus the immediate post-session measurement (p = 0.013). Regarding biomarkers, only cortisol and leptin levels demonstrated a decrease, IH acutely reduced cortisol and leptin while increasing adiponectin levels in pwPD, with no significant changes in BDNF, IL-6, or iron. CONCLUSION: A single IH session is a safe and effective method for inducing hypoxia and modulating biomarkers in pwPD, without disrupting sleep behavior. These findings support the safety of the protocol and encourage investigation into long-term IH, particularly its potential to induce sustained physiological adaptations and its role in sleep management.