Key result
Weightlessness during spaceflight increases heart rate by ~3 bpm while chronic simulations decrease cardiac output.
Why the study?
Microgravity impacts the cardiovascular system via fluid shift and weightlessness, leading to cardiac dysfunction, vascular remodeling, and altered cardiovascular autonomic modulation, which endangers astronaut health.
Does weightlessness (spaceflight or simulation) alter cardiovascular anatomy, function, and autonomic modulation in humans?
Meta-Analysis (n=963)
Does weightlessness (spaceflight or simulation) alter cardiovascular anatomy, function, and autonomic modulation in humans?
Mean Difference: 3.44
p-value: p=0.01
Weightlessness from spaceflight or simulation induces cardiovascular deconditioning, including increased heart rate and decreased stroke volume, similar to aging and immobility.
Supports enhanced astronaut CV monitoring and countermeasures; reinforces parallels with aging/immobility for terrestrial research.
Background: The microgravity environment has a direct impact on the cardiovascular system due to the fluid shift and weightlessness that results in cardiac dysfunction, vascular remodeling, and altered Cardiovascular autonomic modulation (CAM), deconditioning and poor performance on space activities, ultimately endangering the health of astronauts. Objective: This study aimed to identify the acute and chronic effects of microgravity and Earth analogues on cardiovascular anatomy and function and CAM. Methods: CINAHL, Cochrane Library, Scopus, Science Direct, PubMed, and Web of Science databases were searched. Outcomes were grouped into cardiovascular anatomic, functional, and autonomic alterations, and vascular remodeling. Studies were categorized as Spaceflight (SF), Chronic Simulation (CS), or Acute Simulation (AS) based on the weightlessness conditions. Meta-analysis was performed for the most frequent outcomes. Weightlessness and control groups were compared. Results: 62 articles were included with a total of 963 participants involved. The meta-analysis showed that heart rate increased in SF [Mean difference (MD) = 3.44; p = 0.01] and in CS (MD = 4.98; p < 0.0001), whereas cardiac output and stroke volume decreased in CS (MD = −0.49; p = 0.03; and MD = −12.95; p < 0.0001, respectively), and systolic arterial pressure decreased in AS (MD = -5.20; p = 0.03). According to the qualitative synthesis, jugular vein cross-sectional area (CSA) and volume were greater in all conditions, and SF had increased carotid artery CSA. Heart rate variability and baroreflex sensitivity, in general, decreased in SF and CS, whereas both increased in AS. Conclusion: This review indicates that weightlessness impairs the health of astronauts during and after spaceflight, similarly to the effects of aging and immobility, potentially increasing the risk of cardiovascular diseases. Systematic Review Registration: https://www.crd.york.ac.uk/prospero/ , identifier CRD42020215515.
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Zambetta et al. (2024) conducted a meta-analysis in Healthy adults exposed to weightlessness (n=963). Weightlessness (microgravity and Earth analogues) vs. Earth gravity (baseline or control groups) was evaluated on Heart rate in space flight (MD 3.44, p=0.01). Weightlessness during space flight significantly increased heart rate (MD 3.44), while chronic simulations decreased cardiac output and stroke volume, indicating cardiovascular impairment.
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