Cardiovascular adaptations
Also: CV risk
Gravity FieldsRadiationCardiovascularIn-flightEntry, Descent & LandingPostflight RecoveryLifetime SurveillanceLEO long-durationLunar surfaceMars transit & surfacePublicClinicianResearcher
- Orthostatic intolerance after long flights is common. On landing day, 2 of 6 ISS astronauts completed a tilt test, versus 52 of 65 Shuttle astronauts. ◆◆◆◇ Moderate · F
- Jugular vein flow stasis is frequent in flight, and clots have occurred. ◆◆◇◇ Low · F
- Whether space radiation raises long-term heart disease risk is unresolved. ◆◇◇◇ Very low · M E
Proposed certainty (◆ High → ◇ Very low) and evidence-type tags: F flight · A analog · M model/animal · C computational · E expert/operational/standards. AI-proposed, pending reviewer confirmation. How to read the grades.
NASA risk title (verbatim)
Risk of Cardiovascular Adaptations Contributing to Adverse Mission Performance and Health Outcomes
NASA short title: Cardiovascular · HRP element: Human Health Countermeasures (HHC) · Status: Active [current research ongoing] [1]
What it is
In weightlessness, body fluids shift toward the head. That changes blood volume, flow and pressure, and over time the heart and blood vessels adapt [1]. The practical results are cardiovascular deconditioning, light-headedness or fainting on standing after landing (orthostatic intolerance), and lower exercise capacity [1]. NASA has folded three former risks into this one: orthostatic intolerance, heart rhythm problems, and degenerative heart and vessel effects of radiation [1].
Current evidence
- On current ISS missions, these functional problems recover over weeks to months with reconditioning. Much less is known for missions over a year, beyond low Earth orbit (over 14 days) or in partial gravity (over 3 days) [1].
- Orthostatic intolerance is common after long flights. On landing day, 2 of 6 ISS astronauts completed a 10-minute tilt test, compared with 52 of 65 Space Shuttle astronauts [4].
- Jugular veins swell in flight. Flow was stagnant or reversed in 6 of 11 crew, and 1 had an occlusive clot [5].
- In long-duration ISS astronauts, carotid and brachial artery structure and function did not change, although markers of oxidative stress and inflammation rose in flight [6]. The Twins Study astronaut showed carotid distension and thicker carotid walls [7].
- Astronaut death records do not show more cardiovascular deaths, but missions were mostly 4–6 months and follow-up has been limited [1].
- On Earth, radiation doses of 0.5 Gy or more are linked to atherosclerosis later in life. NCRP (2018) found insufficient evidence that heart doses of 0.5 Gy or less cause cardiovascular disease [1].
NASA’s risk posture
NASA scores each risk for each design reference mission (DRM) as likelihood × consequence (LxC). Both run from 1 (lowest) to 5 (highest) on the HSRB’s 5×5 matrix [1][3]. Each score comes with a disposition, such as “Accepted”, “Requires Characterization” or “Requires Mitigation”. These ratings were last approved by NASA’s Human System Risk Board (HSRB) in 5/2024 [1].
| Mission | Duration | In-mission (operations) | Long-term health |
|---|---|---|---|
| LEO | Short (under 30 d) | 3x3 · Requires Characterization | 1x2 · Accepted |
| LEO | Long (30 d–1 yr) | 4x3 · Requires Characterization | 1x2 · Accepted with Monitoring |
| Lunar orbit | Short | 3x3 · Requires Characterization | 1x2 · Accepted with Monitoring |
| Lunar orbit | Long | 4x3 · Requires Characterization | 1x2 · Accepted with Monitoring |
| Lunar orbit + surface | Short | 3x3 · Requires Characterization | 1x2 · Accepted with Monitoring |
| Lunar orbit + surface | Long | 4x3 · Requires Characterization | 1x2 · Accepted with Monitoring |
| Mars preparatory | Under 1 yr | 4x3 · Requires Characterization | 1x2 · Accepted with Monitoring |
| Mars planetary | 730–1,224 d | 4x4 · Requires Mitigation/Standard Refinement | 2x4 · Requires Mitigation/Standard Refinement |
Copied from the Human Research Roadmap on 2026-10-14. Ratings change. Check the live record before citing.
Open knowledge gaps
NASA lists 6 knowledge gaps for this risk, 6 of them open as of 2026-10-14 [1]. Each gap ID links to its page on the Human Research Roadmap (HRR).
Show NASA’s gap list (verbatim)
| Gap | NASA gap statement | Status |
|---|---|---|
| CV-101 | Determine whether long-duration weightlessness and/or reduced gravity induces cardiovascular structural and functional adaptations that contribute to an increased risk of a cardiovascular event or and disease. | Open |
| CV-102 | Determine whether space radiation induces cardiovascular structural and functional adaptations and/or oxidative stress and damage (OSaD)/inflammation that contribute to an increased risk of a cardiovascular event or and disease. | Open |
| CV-103 | Determine whether the combined effects of space radiation and altered gravity induce additive or synergistic effects on the cardiovascular system that contribute to an increased risk of a cardiovascular event or and disease. | Open |
| CV-202 | Identify, develop, and test candidate countermeasures in a spaceflight analog, including monitoring strategies, that prevent or mitigate spaceflight- and/or radiation-induced cardiovascular structural and functional adaptations that contribute to an increased risk of a cardiovascular event and/or disease. | Open |
| CV-203 | Evaluate candidate countermeasures in astronauts, including monitoring strategies, that prevent or mitigate spaceflight- and/or radiation-induced cardiovascular structural and functional adaptations in a spaceflight environment that contribute to an increased risk of a cardiovascular event and/or disease. | Open |
| CV-301 | Validate an integrated countermeasure suite, including monitoring strategies, that prevent or mitigate the spaceflight and/or radiation-induced cardiovascular structural and functional adaptations in a spaceflight environment that contribute to an increased risk of a cardiovascular event and/or disease. | Open |
See also Open questions.
Active countermeasure research
- A stepwise plan. NASA’s approach is to (1) characterize weightlessness and radiation effects alone and combined, (2) test countermeasures in ground analogs and low Earth orbit, and (3) validate them on Gateway and Artemis missions [1].
- Tools for this. Planned work uses bed rest, rodent hindlimb suspension, parabolic flight and long-duration flight. Venous thrombosis and orthostatic intolerance after landing in partial gravity are flagged priorities. HRR lists linked tasks such as “Venous Thrombus - LEO” and “Lunar OI” [1].
Project-level detail, including status, investigators and results, is in the NASA Task Book and on each HRR gap page.
Clinical articles
For practical, clinic-facing guidance, see:
Evidence profile
- Overall certainty
- ◆◆◇◇ Low (proposed)
- Evidence types
- F · Flight dataA · Terrestrial analogM · Model / animalE · Expert / operational / standards
- Literature through
- 2026-10-14
- NASA source
- Human Research Roadmap risk page (last published 05/13/25; read 2026-10-14)
Requirements referenced 3
| Requirement | Title | Plain-language meaning |
|---|---|---|
| [V1 3003] (n) | In-Mission Preventive Health Care | Includes monitoring for venous patency (jugular thrombosis). |
| [V2 7042] | Orthostatic Intolerance Countermeasures | Vehicle must provide countermeasures when transitioning from weightlessness to gravity (e.g., garments, fluid loading support). |
| [V1 4003] | In-Mission Aerobic Capacity | Maintain at least 80% of preflight VO2max. |
IDs as published in NASA-STD-3001 Vol. 1 Rev C (2023-09-15) and NASA-STD-3001 Vol. 2 Rev F (2026-07-14). NASA-STD-3001 binds NASA programs; it is not a regulation for commercial flights. Paraphrased. Standards quick reference.
References 7
- NASA Human Research Roadmap. Risk record: “Risk of Cardiovascular Adaptations Contributing to Adverse Mission Performance and Health Outcomes”. Accessed 2026-10-14. humanresearchroadmap.nasa.gov/Risks/?i=179 NASA E
- NASA Human Research Program. Evidence report for the Cardiovascular risk (approved December 15, 2022). humanresearchroadmap.nasa.gov/evidence/reports/Cardio%20Risk… NASA E
- Antonsen EL, et al. Updates to the NASA human system risk management process for space exploration. NPJ Microgravity. 2023;9:72. doi:10.1038/s41526-023-00305-z PMID:37679359 Peer-reviewed E
- Lee SMC, et al. Orthostatic intolerance after ISS and Space Shuttle missions. Aerosp Med Hum Perform. 2015;86(12 Suppl):A54–A67. doi:10.3357/AMHP.EC08.2015 PMID:26630196 Peer-reviewed F
- Marshall-Goebel K, et al. Assessment of jugular venous blood flow stasis and thrombosis during spaceflight. JAMA Netw Open. 2019;2(11):e1915011. doi:10.1001/jamanetworkopen.2019.15011 PMID:31722025 Peer-reviewed F
- Lee SMC, et al. Arterial structure and function during and after long-duration spaceflight. J Appl Physiol. 2020;129(1):108–123. doi:10.1152/japplphysiol.00550.2019 PMID:32525433 Peer-reviewed F
- Garrett-Bakelman FE, et al. The NASA Twins Study: a multidimensional analysis of a year-long human spaceflight. Science. 2019;364(6436):eaau8650. doi:10.1126/science.aau8650 PMID:30975860 Peer-reviewed F
Machine-checked on 2026-10-14: each URL resolved, each DOI's title/journal/year matched via Crossref, and claims were checked against the source text (abstract or full NASA page). Human verification against full text is still required before review. NASA documents are U.S. Government works (public domain) and are summarized with attribution; journal articles are summarized, not reproduced.
Article info
- Authors
- Pending (AI-assisted draft)
- Reviewer
- Pending review
- Last reviewed
- Pending review
- Literature through
- 2026-10-14
- AI-assisted
- Yes (disclosed)
- COI
- Pending
- License
- CC BY-SA 4.0
- Use
- Educational only · Disclaimer
- Cite this version
- Pending first edition