Intermittent Hypoxia Revisited, A Promising Non-Pharmaceutical Strategy to Reduce Cardio-Metabolic Risk Factors?
Authors: Guillaume Costalat, Frederic Lemaitre, Barbara Tobin, Gillian Mary Claire Renshaw
DOI / Source: https://doi.org/10.1007/s11325-017-1459-8
Date: 05 January 2017
Reading level: Intermediate
Why This Matters for Freedivers
Freedivers often use repeated breath-holds as a form of intermittent hypoxia, but “intermittent hypoxia” can be either harmful or helpful depending on the dose and pattern. This paper is a good reminder that moderate, controlled hypoxic exposure may improve some cardiovascular risk markers (like systolic blood pressure and LDL cholesterol), while more severe patterns (like sleep apnea-type hypoxia) are linked to negative outcomes. It reinforces the idea that if you’re using hypoxia as training, the “dose” matters.
Synopsis
Intermittent hypoxia (IH) gets a bad reputation because it’s a hallmark of obstructive sleep apnea: repeated drops in oxygen night after night are associated with cardiovascular and metabolic problems. But research also shows that low-dose IH—carefully controlled and much less severe—can act like a form of conditioning and may produce beneficial adaptations.
This short study tested whether a brief course of moderate intermittent hypoxia could improve cardio-metabolic risk factors in people who were overweight or obese. Six participants completed a structured protocol over a few weeks: first a sham phase (breathing normal air through a mask), then ten IH sessions across two weeks. Each IH session was designed to give a consistent “hypoxic dose” by targeting an average oxygen saturation around 80% over roughly 70 minutes using repeated cycles of desaturation and re-oxygenation. A key design choice here was that the timing of hypoxic and normoxic periods was individualized so each person actually reached similar oxygen levels, rather than using fixed time cycles that might produce very different doses across individuals.
The results split into two time scales: - After a single IH session: blood glucose dropped and lactate rose—suggesting a temporary shift toward more glycolytic metabolism during/after the hypoxic exposure. - After ten IH sessions: there was no sustained change in baseline glucose, but there were improvements in lipid and blood pressure markers: LDL cholesterol decreased, the LDL/HDL ratio improved, and systolic blood pressure fell.
The authors conclude that a short course of moderate intermittent hypoxia appears feasible and may reduce key cardiovascular risk factors in this population. They also emphasize the “dose” concept: not all intermittent hypoxia is the same, and protocols should be defined in a way that produces a consistent physiological exposure.
Abstract
Purpose: The study aims to investigate the effects of moderate intermittent hypoxia (IH) on key cardio-metabolic risk factors in overweight and obese subjects.
Methods: Six subjects were exposed to 10 sessions of moderate IH over 2 weeks (based on SpO2 = 80%; ~70 min per session). Measures were made of blood glucose (GLU) and lactate (La−); high (HDLc) and low-density lipoproteins (LDLc); triglycerides (TRG), systolic (SBP), and diastolic blood pressure (DBP); and cardiac autonomic indices [root mean square of successive R-R interval differences (RMSSD) and short-term fractal scaling exponent (DFAα1)].
Results: GLU decreased and La− increased following a single IH session, but no sustained change after 10 sessions of IH occurred. Conversely, LDLc, LDLc/HDLc ratio, and SBP were all significantly decreased after 10 sessions.
Conclusion: A short course of recurrent IH appears to be a safe and effective non-pharmacological method of reducing key cardiovascular risk factors associated with metabolic disorders.