TABLE 2.
The effects of intermittent hypoxia-hyperoxia training (IHHT) on aging markers and age-related diseases.
| Author, year (ref.) | Condition | Age in years | Study design | Type of hypoxia | Hypoxia protocol | Aging markers | Results | Conclusion | Safety issues |
| Dudnik et al., 2018 | Cardiac patients with comorbidities | Mean 66 (IHHT), 65 (control) | RCT | IHHT | 15 sessions hypoxia (11–12% O2)—hyperoxia (30–33% O2) for 5 weeks: 3 sessions/week, 5–7 hypoxic periods of 4–6 min, 3 min hyperoxic recovery. | CRF | CRF in the IHHT group was not significantly different compared with the control group. Systolic and diastolic blood pressures were not significantly different between groups after treatment. | IHHT might be a suitable option for older patients who cannot exercise. A 5-week IHHT is as effective as an 8-week exercise program in improving CRF, without hematological changes. | Safe |
| Hgb, RBC, reticulocyte | Hgb content was not significantly different between groups. RBC and reticulocytes did not change pre/post interventions in both experimental groups. | ||||||||
| Glazachev et al., 2017 | coronary artery disease (CAD) | 43–83 | Non-RCT | IHHT | 15 sessions hypoxia (10% O2)- hyperoxia (30% O2). 3 sessions/week, 5–7 hypoxic periods lasting 4–6 min, with 3-min hyperoxic recovery. | Exercise performance | The IHHT showed improved exercise capacity, reduced systolic and diastolic blood pressures, enhanced left ventricle ejection fraction, but only at 1-month follow-up. |
IHHT is associated with improved exercise tolerance, healthier risks factors profile, and a better quality of life. The study also suggests that IHHT is as effective as an 8-week standard rehabilitation program in CAD patients. | Safe |
| Blood markers (RBC, Hgb, reticulocyte); metabolic profiles (total cholesterol, LDL and HDL, triglycerides, and glucose) | Hgb and glycemia were unchanged after IHHT, but glycemia was significantly lower at the 1-month follow-up. Total cholesterol and LDL were lower after IHHT. At the 1-month follow-up total cholesterol was similar to pretreatment. Reticulocytes were significantly higher in the IHHT at the end of treatment and at 1-month follow-up. | ||||||||
| Quality of life | The SAQ profile was improved and not significantly different to the control after standard rehabilitation. The IHHT was compared to the control at 1-month follow-up, and no differences were found. |
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| Serebrovska et al., 2019 | Prediabetic patients | 51–74 | RCT | IHHT and IHNT | 15 sessions IHHT and IHNT, 5 times/week for 3 weeks. Each session consisted of 4 cycles of 5 min of 12% FiO2 followed by 3 min of 33% O2 in nitrogen or 5 min of normoxia. | Serum total cholesterol, HDL, LDL, and triglycerides | The study showed the same positive effect of IHNT and IHHT: decreased total blood cholesterol and LDL; and an equally smaller drop in SpO2 during acute hypoxic test. Improved parameters persisted 1 month after training termination in both groups. | One of the advantages of IHHT over IHT observed in this study could be some reduction in the duration of the sessions due to shortening re-oxygenation periods. | Not mentioned |
| Plasma glucose concentrations | The study showed the same positive effect of IHHT and IHNT: equal reduction of serum glucose concentrations, both fasting and 2 h of OGTT. Improved parameters persisted 1 month after training termination in both groups. | ||||||||
| Susta et al., 2020 | Healthy | 18–24 | Uncontrolled CT | IHHT and IHNT | FIO2 11% for up to 7 min followed by 3–5 min of exposure to normoxia (room air) or hyperoxia, FIO2 30–35% | Oxidative stress (concentration of hydroperoxides) | Oxidative stress was similar after IHN and IHH exposures compared with baseline values. | Hypoxia (IHN and IHH) cause neither pronounced oxidative stress nor antioxidant capacity impairment in healthy humans. | Safe |
| Antioxidant capacity | The antioxidant capacity was also similar between experimental groups after both modalities of exposure. |
IHHT, intermittent hypoxia-hyperoxia; IHNT, intermittent hypoxia-normoxia training; RCT, randomized controlled clinical trial; CRF, cardiorespiratory fitness; RBC, red blood cells; Hgb, hemoglobin; Hct, hematocrit; SAQ, Seattle Angina Questionnaire.