Effects of Intermittent Normobaric Hypoxia on Health-Related Outcomes in Healthy Older Adults: A Systematic Review

BACKGROUND: Aging is a degenerative process that is associated with an increased risk of diseases. Intermittent hypoxia has been investigated in reference to performance and health-related functions enhancement. This systematic review aimed to summarize the effect of either passive or active intermittent normobaric hypoxic interventions compared with normoxia on health-related outcomes in healthy older adults. METHODS: Relevant studies were searched from PubMed and Web of Science databases in accordance with PRISMA guidelines (since their inceptions up until August 9, 2022) using the following inclusion criteria: (1) randomized controlled trials, clinical trials and pilot studies; (2) Studies involving humans aged > 50 years old and without any chronic diseases diagnosed; (3) interventions based on in vivo intermittent systemic normobaric hypoxia exposure; (4) articles focusing on the analysis of health-related outcomes (body composition, metabolic, bone, cardiovascular, functional fitness or quality of life). Cochrane Collaboration recommendations were used to assess the risk of bias. RESULTS: From 509 articles initially found, 17 studies were included. All interventions were performed in moderate normobaric hypoxia, with three studies using passive exposure, and the others combining intermittent hypoxia with training protocols (i.e., using resistance-, whole body vibration- or aerobic-based exercise). CONCLUSIONS: Computed results indicate a limited effect of passive/active intermittent hypoxia (ranging 4–24 weeks, 2–4 days/week, 16–120 min/session, 13–16% of fraction of inspired oxygen or 75–85% of peripheral oxygen saturation) compared to similar intervention in normoxia on body composition, functional fitness, cardiovascular and bone health in healthy older (50–75 years old) adults. Only in specific settings (i.e., intermediate- or long-term interventions with high intensity/volume training sessions repeated at least 3 days per week), may intermittent hypoxia elicit beneficial effects. Further research is needed to determine the dose–response of passive/active intermittent hypoxia in the elderly. Trial registration. Systematic review registration: PROSPERO 2022 CRD42022338648.