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Cited by 51Spaceflight effects on biologyBone health and osteoporosis researchSpace Exploration and Technology

A human mission to Mars: Predicting the bone mineral density loss of astronauts

Open access
Axpe, Eneko, Chan, Doreen, Abegaz, Metadel F., Schreurs, Ann-Sofie, Alwood, Joshua S., Globus, Ruth K., Appel, Eric A.·2020·PLOS ONE
DOI 10.1371/journal.pone.0226434PMC PMC6975633
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Abstract

A round-trip human mission to Mars is anticipated to last roughly three years. Spaceflight conditions are known to cause loss of bone mineral density (BMD) in astronauts, increasing bone fracture risk. There is an urgent need to understand BMD progression as a function of spaceflight time to minimize associated health implications and ensure mission success. Here we introduce a nonlinear mathematical model of BMD loss for candidate human missions to Mars: (i) Opposition class trajectory (400-600 days), and (ii) Conjunction class trajectory (1000-1200 days). Using femoral neck BMD data (N = 69) from astronauts after 132-day and 228-day spaceflight and the World Health Organization's fracture risk recommendation, we predicted post-mission risk and associated osteopathology. Our model predicts 62% opposition class astronauts and 100% conjunction class astronauts will develop osteopenia, with 33% being at risk for osteoporosis. This model can help in implementing countermeasure strategies and inform space agencies' choice of crew candidates.

AI snapshot

Written from the paper’s full text.

TL;DR

A nonlinear exponential-decay model predicts femoral neck bone mineral density (BMD) loss for human Mars missions, using existing astronaut BMD data and WHO fracture-risk criteria. It predicts substantial osteopenia/osteoporosis risk, especially for longer conjunction-class missions.

Key findings

  • For a conjunction-class Mars mission (1000–1200 days), the model predicts 32.4–36.8% femoral neck BMD loss and T-scores from -1.49 to -2.93; 100% of astronauts develop osteopenia, 33% are at risk for osteoporosis, and T-scores < -2 (NASA’s non-permissible outcome) are predicted for 79% of analyzed conjunction-class cases.
  • For an opposition-class mission (400–600 days), predicted femoral neck BMD loss is 15.6–22.0%, with T-scores from -0.08 to -2.01; 62% develop osteopenia, and none are predicted to develop osteoporosis.
  • The fitted exponential model parameters are decay rate λ = 6.371×10⁻⁴, half-life = 1088 days, and time constant = 1570 days, with a plateau assumed at 69.0% BMD loss.
  • Lowest fracture risk is predicted for non-Hispanic 30–39-year-old black males; highest risk for non-Hispanic 40–49-year-old white females.

Methods

  • A one-phase exponential decay model was formulated for areal BMD in weight-bearing bones, assuming a plateau of 69.0% BMD loss relative to pre-flight BMD; the femoral neck was chosen because WHO recommends it for T-score fracture-risk assessment.
  • The model used N = 69 femoral neck BMD loss values from astronauts in prior spaceflights (Table 1; durations including 132–228-day missions), and nonlinear regression estimated the decay rate.
  • T-scores were calculated using NHANES reference data and WHO criteria, then predicted for opposition-class (400–600 days) and conjunction-class (1000–1200 days) Mars trajectories; unpaired t tests between groups for 400-, 600-, 1000-, and 1200-day predictions gave p < 0.0001 in all cases.

Limitations

  • The paper states that the model does not account for exercise, pharmaceutical (e.g., bisphosphonate), or dietary countermeasures; the data predate ARED implementation in 2009; countermeasures beyond 1 year are untested; person-to-person variability is large; deep-space radiation is not included because data come from low Earth orbit; spaceflight data are limited; pre-flight BMD inputs come from NHANES rather than individual astronauts; and bone quality/microarchitecture are not modeled.
  • Evident from the text: the model extrapolates from short-duration LEO astronaut data to multi-year Mars missions without direct validation, and T-score predictions depend on reference-database means rather than actual crew pre-launch BMD.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1371/journal.pone.0226434

Cites

33 of 33 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

11 of 40 cited sources checked · 5 supported · 0 flagged · accuracy not yet measured

  • Premisecitation

    BMD loss is an established fracture risk factor due to bone weakening, as shown by large epidemiological studies correlating BMD with the incidence of fragility fractures.

    “BMD loss is an established fracture risk factor due to bone weakening as measured in large epidemiological studies correlating BMD with the incidence of fragility fractures [2–4].”
    Quote in the paperSubstantial claim1 of 3 sources checked
    • cites [2] JH Keyak, 2009, Reduction in proximal femoral strength due to long-duration spaceflight, Bone source
    • cites [3] PR Cavanagh, 2005, Exercise and pharmacological countermeasures for bone loss during long-duration space flight, Gravit Space Biol Bull
    • cites [4] JD Sibonga, 2007, Adaptation of the Skeletal System During Long-Duration Spaceflight, Clin Rev Bone Miner Metab source

      The Background (pp. 4–5) links bone loss and weakened bone structure to increased fracture incidence, and the Abstract (p. 2) says declines in volumetric BMD reduce estimated hip strength. The paper does not report large epidemiological studies correlating BMD with fragility-fracture incidence, so that specific basis for the claim is not supported by our copy. (LLM, conf=0.83)

      Experimental — accuracy not yet measured
  • Premisecitation

    Current standards to monitor and maintain bone health in NASA and ISS crewmembers are based on BMD measurements by dual-energy x-ray absorptiometry (DXA).

    “Current standards to monitor and maintain bone health in both NASA and ISS crewmembers are based in BMD measurements by dual-energy x-ray absorptiometry (DXA) [5].”
    Quote in the paperNot a substantial claim1 of 1 sources checked
    • cites [5] T Lang, 2017, Towards human exploration of space: the THESEUS review series on muscle and bone research priorities, npj Microgravity source

      The “Early findings of bone loss in long-duration missions” section describes pre- and post-flight DXA BMD measurements, and “Countermeasure studies” reports DXA measurements used to assess bone-loss interventions in ISS crews. These passages support the use of DXA BMD to monitor bone health, but they do not establish that current NASA and ISS standards for monitoring and maintaining bone health are based on it. No page numbers were provided in our copy. (LLM, conf=0.83)

      Experimental — accuracy not yet measured
  • Premisecitation

    BMD recovery on Earth in astronauts' bones after spaceflight is well described by an exponential function.

    “In contrast, BMD recovery on Earth in the bones of various astronauts after spaceflights is well described by an exponential function [19].”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [19] JD Sibonga, 2007, Recovery of spaceflight-induced bone loss: Bone mineral density after long-duration missions as fitted with an exponential function, Bone source
  • Study design and conductcitation

    The person-to-person variability of BMD loss observed in the available data is large.

    “An additional limitation of our model is that the person-to-person variability of BMD loss observed in the available data [19,32,33] is large (see Fig 1).”
    Quote in the paperNot a substantial claim1 of 3 sources checked
    • cites [19] JD Sibonga, 2007, Recovery of spaceflight-induced bone loss: Bone mineral density after long-duration missions as fitted with an exponential function, Bone source

      The Discussion (page unavailable) identifies three crew members as outliers with proximal-femur BMD losses exceeding 15%, supporting variation in loss across people. Its explicit statement that outcomes are 'highly variable among crew members' refers to skeletal recovery, however, not to the overall person-to-person variability of BMD loss claimed here. (LLM, conf=0.78)

      Experimental — accuracy not yet measured
    • cites [32] AE Nicogossian, 1993

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

    • cites [33] TF Lang, 2006, Adaptation of the proximal femur to skeletal reloading after long-duration spaceflight, J Bone Miner Res source
  • Premisereasoning

    The mathematical model presented is the first to the authors' knowledge that does not assume a linear decrease in BMD of astronauts.

    “The mathematical model presented is the first to our knowledge that does not assume a linear decrease in the BMD of astronauts [28–30].”
    Quote in the paperSubstantial claim1 of 3 sources checked
    • cites [28] JD Sibonga, 2018, Evidence Report: Risk of Bone Fracture due to Spaceflight- induced Changes to Bone
    • cites [29] ES Orwoll, 2013, Skeletal health in long-duration astronauts: Nature, assessment, and management recommendations from the NASA bone summit, J Bone Miner Res source

      In “Long-Duration Astronaut Data: Bone Loss and Recovery” (page unavailable), the paper says an average monthly BMD-loss rate was used to predict loss for other mission designs, while noting there were insufficient measurements to determine whether loss during flight was linear. This supports the contrast with rate-based predictions, but the paper does not establish that the citing authors’ model was the first not to assume a linear decrease. (LLM, conf=0.79)

      Experimental — accuracy not yet measured
    • cites [30] L Vico, 2018, Skeletal changes during and after spaceflight, Nat Rev Rheumatol source
  • May combine two claims. 14
  • Classified as probably not a substantial claim. 7
  • The quote only partly states this claim. 1

  • May combine two claims.

    Premisecitation

    Areal bone mineral density (BMD) is a measurable, critical component of bone strength.

    “A measurable, critical component for the bone strength is the areal bone mineral density (BMD) [1].”
    Quote in the paperSubstantial claim1 of 1 sources checked
    • cites [1] G Osterhoff, 2016, Bone mechanical properties and changes with osteoporosis, Injury source

  • May combine two claims.

    Premisecitation

    Long-duration spaceflights induce bone mineral density (BMD) loss in weight-bearing bones, with considerable individual variability.

    “It is well known that long-duration spaceflights induce BMD loss in weight-bearing bones although there is considerable individual variability [6–12].”
    Quote in the paperSubstantial claim3 of 7 sources checked
    • cites [6] JD Sibonga, 2007, Recovery of spaceflight-induced bone loss: Bone mineral density after long-duration missions as fitted with an exponential function, Bone source
    • cites [7] W Li, 2007, Voxel-based modeling and quantification of the proximal femur using inter-subject registration of quantitative CT images, Bone source
    • cites [8] R Dana Carpenter, 2010, Long-term changes in the density and structure of the human hip and spine after long-duration spaceflight, Acta Astronaut source
    • cites [9] Q Zhao, 2010, A statistical method (cross-validation) for bone loss region detection after spaceflight, Australas Phys Eng Sci Med source

      The longitudinal-study section says astronauts experience localized bone mineral loss during extended weightlessness, including in the proximal femur. The discussion identifies load-bearing subregions as sites of the largest losses. Although the paper calculates variance across astronauts, the passages do not establish that individual variability is considerable. (LLM, conf=0.86)

      Experimental — accuracy not yet measured
    • cites [10] T Lang, 2004, Cortical and Trabecular Bone Mineral Loss From the Spine and Hip in Long-Duration Spaceflight, J Bone Miner Res source
    • cites [11] TF Lang, 2006, Adaptation of the Proximal Femur to Skeletal Reloading After Long-Duration Spaceflight, J Bone Miner Res source
    • cites [12] JD Sibonga, 2013, Spaceflight-induced Bone Loss: Is there an Osteoporosis Risk?, Curr Osteoporos Rep source

  • Classified as probably not a substantial claim. May combine two claims.

    Premisecitation

    Femoral neck is recommended by the World Health Organization (WHO) to determine the fragility fracture risk associated T-score and to diagnose osteoporosis in clinical practice.

    “Femoral neck was chosen between other weight-bearing bones because it is the recommended by the World Health Organization (WHO) [25] to determine the fragility fracture risk associated T-score, as well as to diagnose osteoporosis in clinical practice [18].”
    Quote in the paperSubstantial claim1 of 2 sources checked
    • cites [25] T Sözen, 2017, An overview and management of osteoporosis, Eur J Rheumatol source
    • cites [18] ES Nelson, 2009, Development and Validation of a Predictive Bone Fracture Risk Model for Astronauts, Ann Biomed Eng source

  • May combine two claims.

    Premisecitation

    The maximum total BMD loss has been previously estimated to be 69.0% relative to astronauts' pre-flight BMD, obtained by combining data from different large studies in humans.

    “The maximum total BMD loss has been previously estimated to be 69.0% relative to the astronauts’ pre-flight BMD [18], and obtained by combining data from different large studies in humans [23,24].”
    Quote in the paperSubstantial claim1 of 3 sources checked
    • cites [18] ES Nelson, 2009, Development and Validation of a Predictive Bone Fracture Risk Model for Astronauts, Ann Biomed Eng source
    • cites [23] SR Cummings, 2002, Improvement in spine bone density and reduction in risk of vertebral fractures during treatment with antiresorptive drugs, Am J Med source
    • cites [24] NC Wright, 2014, The recent prevalence of osteoporosis and low bone mass in the United States based on bone mineral density at the femoral neck or lumbar spine, J Bone Miner Res source

      The Methods describe a large human BMD study using NHANES 2005–2010 data and Census counts. That supports citing this paper as a human population study, but our copy does not describe combining studies to estimate astronauts’ maximum BMD loss. The 69.0% figure is attached to a different citation, [18], in the citing sentence. (LLM, conf=0.79)

      Experimental — accuracy not yet measured

  • May combine two claims. The quote only partly states this claim.

    Findingown data

    The nonlinear regression yielded a BMD decay rate λ of 6.371×10−4, a half-life of 1088 days, and a time constant of 1570 days.

    “| Decay rate, λ | 6.371∙10−4 (a.u.) |”
    • Also stated in: § Results · plain
      “| Half life, t1⁄2 | 1088 days |”
    • Also stated in: § Results · plain
      “| Time constant, τ | 1570 days |”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: BMD loss will eventually plateau at the maximum value of 69.0% relative to pre-flight BMD.

  • May combine two claims.

    Findingown data

    Percent loss in BMD at femoral neck in astronauts (N = 69) after 400, 600, 1000, and 1200 day-spaceflights were statistically analyzed via unpaired t tests between all groups, with a two-tailed p value of p < 0.0001 observed in all cases.

    “Percent loss in bone mineral density at fermoral neck in astronauts (N = 69) after 400, 600, 1000 and 1200 day-spaceflights were statistically analyzed via unpaired t tests between all groups, whereby a two-tailed p value of p < 0.0001 was observed in all cases.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Premisecitation

    BMD loss in the femoral neck has been modeled as a linear decrease of (1.06 ± 0.63)% per month.

    “Specifically, BMD loss in the femoral neck has been modeled as a linear decrease: (1.06 ± 0.63)% BMD loss per month [17,18].”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [17] A LeBlanc, 2000, Muscle volume, MRI relaxation times (T2), and body composition after spaceflight, J Appl Physiol source
    • cites [18] ES Nelson, 2009, Development and Validation of a Predictive Bone Fracture Risk Model for Astronauts, Ann Biomed Eng source

  • May combine two claims.

    Premisereasoning

    Prior work assumed a linear decrease of BMD in astronauts to make predictions, which is not valid for long-duration spaceflights.

    “To our knowledge, each and every prior work assume a linear decrease of the BMD in astronauts to make predictions [13], which is not valid for long duration spaceflights.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [13] AD LeBlanc, Skeletal responses to space flight and the bed rest analog: a review, J Musculoskelet Neuronal Interact

      Couldn’t be matched to a paper in Crossref, so it can’t be checked.

  • May combine two claims.

    Interpretationreasoning

    While some crew are likely to develop osteopenia, none are predicted to develop osteoporosis on an opposition class mission.

    “While some crew are likely to develop osteopenia, none are predicted to develop osteoporosis.”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: BMD loss will eventually plateau at the maximum value of 69.0% relative to pre-flight BMD.

  • May combine two claims.

    Interpretationreasoning

    Non-Hispanic, 30-39 year old black males would have the lowest risk of bone fracture in any of the missions, while non-Hispanic, 40-49 year old white females would have the highest risk among the groups analyzed.

    “Consistent with terrestrial values from the NHANES reference database, non-Hispanic, 30–39 year old black males would have the lowest risk of bone fracture in any of the missions, while non-Hispanic, 40–49 years old, white females would have the highest risk for bone fracture amongst the different groups analyzed.”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: BMD loss will eventually plateau at the maximum value of 69.0% relative to pre-flight BMD.

  • Classified as probably not a substantial claim. May combine two claims.

    Interpretationreasoning

    A bone fracture in an astronaut during a mission to Mars would endanger mission goals and could provoke medical complications that may result in morbidity or mortality.

    “A bone fracture in an astronaut during a mission to Mars would endanger the mission goals and also could provoke medical complications (microgravity’s effect on bone cell performance could impair bone healing or induce sepsis or thromboembolic blood clots) that may result in morbidity or mortality.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    For astronauts landing on the surface of Mars, the risk of fracture increases, as falls or crushes would be more likely to happen in Mars' fractional gravity, especially given the period of disuse during transit to Mars.

    “However, for astronauts landing on the surface of Mars, the risk of fracture increases, as falls or crushes would be more likely to happen in Mars’ fractional gravity (3.71 m/s2 versus 9.81 m/s2 on Earth), especially given the period of disuse during transit to Mars.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Interpretationreasoning

    During missions, the risk of fracture is minimal as sudden mechanical overloads are very unlikely to happen in a microgravity environment.

    “It is important to note that during missions, the risk of fracture is minimal as sudden mechanical overloads are very unlikely to happen in a microgravity environment.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based).

    Interpretationreasoning

    The same logic applies to astronauts after return to Earth, when predicted BMD losses are presumably maximal.

    “The same logic applies to for astronauts after return to Earth, when the predicted BMD losses are presumably maximal.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Premisecitation

    Previous studies have calculated the duration of different strong candidate human missions to Mars.

    “Previous studies have calculated the duration of different strong candidate human missions to Mars [26,27].”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [26] KE Goodliff, 2017 source
    • cites [27] B Mattfeld, 2014, Trades Between Opposition and Conjunction Class Trajectories for Early Human Missions to Mars, Am Inst Aeronaut Astronaut

  • Classified as probably not a substantial claim.

    Premisecitation

    There is evidence that trabecular microarchitecture and bone geometry affect bone strength.

    “There is evidence that trabecular microarchitecture and bone geometry affect the bone strength [34].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [34] V V Shanbhogue, 2015, Bone Geometry, Volumetric Density, Microarchitecture, and Estimated Bone Strength Assessed by HR-pQCT in Adult Patients With Type 1 Diabetes Mellitus, J Bone Miner Res source

  • May combine two claims.

    Interpretationreasoning

    A linear decrease will eventually predict negative BMDs in long-duration spaceflights, which lacks physical meaning.

    “Although a linear decrease is widely used in the literature, it will eventually predict a negative BMDs in long-duration spaceflights, which lacks any physical meaning.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Study design and conductown data

    The potential negative impact of prolonged exposure to deep space radiation on BMD is not taken into account, as all data used were from astronauts in low Earth orbit where some radioprotection is conferred by the magnetosphere.

    “Further, the potential negative impact of prolonged exposure to deep space radiation on BMD is not taken into account, as all of the data used to generate the present model were obtained from astronauts in low earth orbit where some radioprotection is conferred by the magnetosphere.”
    Quote in the paperSubstantial claim
18 of 18

  • The authors state this as an assumption.

    BMD loss will eventually plateau at the maximum value of 69.0% relative to pre-flight BMD.

    “Therefore, assuming that the BMD loss will eventually plateau at this maximum value:”

  • The paper relies on this without support.

    There are no supporting data from astronauts available for time-frames relevant to interplanetary travel.

    “Further, there are no supporting data from astronauts available for time-frames relevant to interplanetary travel (all the candidate missions are in the order of years given current rocket capabilities).”

  • The paper relies on this without support.

    NASA's medical standards establish a non-permissible T-score limit of -2.

    “NASA´s medical standards for crewmember’s health establish a non-permissible T-score limit of -2.”

  • The paper relies on this without support.

    Spinal cord injury provides an example where a plateau in BMD decrements occurs 1.5–2.5 years post-injury, similar to the total duration of a potential human mission to Mars.

    “However, spinal cord injury provides an example where a plateau in BMD decrements occurs 1.5–2.5 years post-injury, which is similar to the total duration of a potential human mission to Mars.”

  • The paper relies on this without support.

    The ability of countermeasure strategies to mitigate BMD loss of astronauts in missions exceeding 1 year in duration has not been tested.

    “The ability of countermeasure strategies to mitigate BMD loss of astronauts in missions exceeding 1 year in duration has not been tested.”
5 of 5

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Table 1 includes a time outside its stated range

    Minor

    The table is described as containing results after 132- to 228-day spaceflights, but its first data row lists 11 days.

  • Methods give positive rather than negative diagnostic thresholds

    Minor

    The Methods state an osteoporosis threshold of < 2.5 and an osteopenia interval beginning above 2.5. The Results instead give the corresponding thresholds as −2.5, consistent with the categories used in Table 3.

2 of 2

Cites

Flagged first, then by citations

Research works printed but not linked: 2

  1. JD Sibonga, 2007, Recovery of spaceflight-induced bone loss: Bone mineral density after long-duration missions as fitted with an exponential function, Bone, 41, 973, 10.1016/j.bone.2007.08.022 · DOI · Paper page
  2. TF Lang, 2006, Adaptation of the proximal femur to skeletal reloading after long-duration spaceflight, J Bone Miner Res, 21, 1224, 10.1359/jbmr.060509 · DOI · Paper page

Cited by

Sorted by citations

Related

Authors
Axpe, E., Chan, D., Abegaz, M. F., Schreurs, A.-S., Alwood, J. S., Globus, R. K., & Appel, E. A.
Affiliations
  • Ames Research Center (US)
  • Stanford University (US)
Corresponding author
  • Globus, Ruth K.
  • Appel, Eric A.
ORCID
Venue
PLOS ONE
Publisher
Public Library of Science (PLoS)
Published
2020-01-22
Volume
15
Issue
1
Pages
e0226434
ISSN
1932-6203 (ISSN-L)
DOI
10.1371/journal.pone.0226434
PMC
PMC6975633
OpenAlex
W3003023841
Semantic Scholar
c55f78491bee2dd42115e3191f9f59b3bd77d5c7
Cited by
51
References
33
Citations by year
2026: 11 · 2025: 10 · 2024: 5 · 2023: 5 · 2022: 12 · 2021: 4 · 2020: 4
FWCI
3.15
Type
journal article
Language
en
Open access
Licence
Locations
  • PLoS ONE (publishedVersion, public-domain)
  • PubMed (publishedVersion)
  • PubMed Central (submittedVersion, public-domain)
  • RePEc: Research Papers in Economics (submittedVersion)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
  • Figshare (submittedVersion, cc-by)
Funders
  • Bill and Melinda Gates Foundation (OPP1113682)
  • Eusko Jaurlaritza
Topics
  • Health Sciences › Medicine › Physiology › Spaceflight effects on biology
  • Health Sciences › Medicine › Orthopedics and Sports Medicine › Bone health and osteoporosis research
  • Physical Sciences › Engineering › Aerospace Engineering › Space Exploration and Technology
Keywords
bone mineral loss, astronauts, Mars missions, spaceflight, femoral neck, osteoporosis, osteopenia, fracture risk
MeSH terms
Adult, Female, Humans, Male, Middle Aged, Osteoporosis

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-10-06.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-10-06.

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Statistics and arithmetic are recomputed, not judged.

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