Insitute of Sport Sciences, Faculty of Biology and Medicine, University of Lausanne, CH-1015, Lausanne, Switzerland.
Insitute of Sport Sciences, Faculty of Biology and Medicine, University of Lausanne, CH-1015, Lausanne, Switzerland; Department of Biomedical Sciences, University of Lausanne, Lausanne, Switzerland.
Ageing Res Rev. 2022 Aug;79:101650. doi: 10.1016/j.arr.2022.101650. Epub 2022 May 18.
Hypoxia is caused by insufficient oxygen availability for the organism leading to reduced oxygen delivery to tissues and cells. It has been regarded as a severe threat to human health and it is indeed implicated in pathophysiological mechanisms involved in the development and progression of many diseases. Nevertheless, the potential of controlled hypoxia interventions (i.e. hypoxia conditioning) for improving cardio-vascular health is gaining increased attention. However, blood rheology is often a forgotten factor for vascular health while aging and hypoxia exposure are both suspected to alter hemorheological properties. These changes in blood rheology may influence the benefits-risks balance of hypoxia exposure in older individuals. The benefits of hypoxia exposure for vascular health are mainly reported for healthy populations and the combined impact of aging and hypoxia on blood rheology could therefore be deleterious in older individuals. This review discusses evidence of hypoxia-related and aging-related changes in blood viscosity and its determinants. It draws upon an extensive literature search on the effects of hypoxia/altitude and aging on blood rheology. Aging increases blood viscosity mainly through a rise in plasma viscosity, red blood cell (RBC) aggregation and a decrease in RBC deformability. Hypoxia also causes an increase in RBC aggregation and plasma viscosity. In addition, hypoxia exposure may increase hematocrit and modulate RBC deformability, depending on the hypoxic dose, i.e, beneficial effect of intermittent hypoxia with moderate dose vs deleterious effect of chronic continuous or intermittent hypoxia or if the hypoxic dose is too high. Special attention is directed toward the risks vs. benefits of hemorheological changes during hypoxia exposure in older individuals, and its clinical relevance for vascular disorders.
缺氧是由于机体供氧不足导致组织和细胞供氧减少引起的。它被认为是对人类健康的严重威胁，实际上与许多疾病的发展和进展有关的病理生理机制有关。然而，控制缺氧干预（即缺氧适应）改善心血管健康的潜力正受到越来越多的关注。然而，血液流变学在衰老和缺氧暴露时往往是血管健康的一个被遗忘的因素，这两种因素都被怀疑改变血液流变学特性。这些血液流变学的变化可能会影响老年个体缺氧暴露的获益-风险平衡。缺氧暴露对血管健康的益处主要是在健康人群中报道的，而衰老和缺氧对血液流变学的综合影响可能对老年个体有害。这篇综述讨论了与缺氧和衰老相关的血液粘度变化及其决定因素的证据。它借鉴了关于缺氧/海拔和衰老对血液流变学影响的广泛文献检索。衰老主要通过增加血浆粘度、红细胞（RBC）聚集和降低 RBC 变形性来增加血液粘度。缺氧也会导致 RBC 聚集和血浆粘度增加。此外，缺氧暴露可能会增加红细胞比容并调节 RBC 变形性，这取决于缺氧剂量，即中剂量间歇性缺氧的有益作用与慢性连续或间歇性缺氧或缺氧剂量过高的有害作用。特别关注老年个体在缺氧暴露期间血液流变学变化的风险与获益，及其对血管疾病的临床相关性。
