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Damgaard V, Mariegaard J, Lindhardsen JM, Ehrenreich H, Miskowiak KW. Neuroprotective Effects of Moderate Hypoxia: A Systematic Review. Brain Sci 2023; 13:1648. [PMID: 38137096 PMCID: PMC10741927 DOI: 10.3390/brainsci13121648] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2023] [Revised: 11/22/2023] [Accepted: 11/23/2023] [Indexed: 12/24/2023] Open
Abstract
Emerging evidence highlights moderate hypoxia as a candidate treatment for brain disorders. This systematic review examines findings and the methodological quality of studies investigating hypoxia (10-16% O2) for ≥14 days in humans, as well as the neurobiological mechanisms triggered by hypoxia in animals, and suggests optimal treatment protocols to guide future studies. We followed the preferred reporting items for systematic reviews and meta-analysis (PRISMA) 2020. Searches were performed on PubMed/MEDLINE, PsycInfo, EMBASE, and the Cochrane Library, in May-September 2023. Two authors independently reviewed the human studies with the following tools: (1) revised Cochrane collaboration's risk of bias for randomized trials 2.0; (2) the risk of bias in nonrandomized studies of interventions. We identified 58 eligible studies (k = 8 human studies with N = 274 individuals; k = 48 animal studies) reporting the effects of hypoxia on cognition, motor function, neuroimaging, neuronal/synaptic morphology, inflammation, oxidative stress, erythropoietin, neurotrophins, and Alzheimer's disease markers. A total of 75% of human studies indicated cognitive and/or neurological benefits, although all studies were evaluated ashigh risk of bias due to a lack of randomization and assessor blinding. Low-dose intermittent or continuous hypoxia repeated for 30-240 min sessions, preferably in combination with motor-cognitive training, produced beneficial effects, and high-dose hypoxia with longer (≥6 h) durations and chronic exposure produced more adverse effects. Larger and methodologically stronger translational studies are warranted.
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Affiliation(s)
- Viktoria Damgaard
- Neurocognition and Emotion in Affective Disorders (NEAD) Centre, Copenhagen Affective Disorder Research Centre, Psychiatric Centre Copenhagen, Frederiksberg Hospital, Hovedvejen 17, DK-2000 Frederiksberg, Denmark; (V.D.); (J.M.)
- Department of Psychology, University of Copenhagen, Øster Farimagsgade 2A, DK-1353 Copenhagen, Denmark
| | - Johanna Mariegaard
- Neurocognition and Emotion in Affective Disorders (NEAD) Centre, Copenhagen Affective Disorder Research Centre, Psychiatric Centre Copenhagen, Frederiksberg Hospital, Hovedvejen 17, DK-2000 Frederiksberg, Denmark; (V.D.); (J.M.)
- Department of Psychology, University of Copenhagen, Øster Farimagsgade 2A, DK-1353 Copenhagen, Denmark
| | - Julie Marie Lindhardsen
- Neurocognition and Emotion in Affective Disorders (NEAD) Centre, Copenhagen Affective Disorder Research Centre, Psychiatric Centre Copenhagen, Frederiksberg Hospital, Hovedvejen 17, DK-2000 Frederiksberg, Denmark; (V.D.); (J.M.)
- Department of Psychology, University of Copenhagen, Øster Farimagsgade 2A, DK-1353 Copenhagen, Denmark
| | - Hannelore Ehrenreich
- University of Göttingen, 37075 Göttingen, Germany;
- Clinical Neuroscience, Max Planck Institute for Multidisciplinary Sciences, City Campus, 37075 Göttingen, Germany
| | - Kamilla Woznica Miskowiak
- Neurocognition and Emotion in Affective Disorders (NEAD) Centre, Copenhagen Affective Disorder Research Centre, Psychiatric Centre Copenhagen, Frederiksberg Hospital, Hovedvejen 17, DK-2000 Frederiksberg, Denmark; (V.D.); (J.M.)
- Department of Psychology, University of Copenhagen, Øster Farimagsgade 2A, DK-1353 Copenhagen, Denmark
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