Causal diagramming for assessing human system risk in spaceflight.

For over a decade, the National Aeronautics and Space Administration (NASA) has tracked and configuration-managed approximately 30 risks that affect astronaut health and performance before, during and after spaceflight. The Human System Risk Board (HSRB) at NASA Johnson Space Center is responsible for setting the official risk posture for each of the human system risks and determining-based on evaluation of the available evidence-when that risk posture changes. The ultimate purpose of tracking and researching these risks is to find ways to reduce spaceflight-induced risk to astronauts. The adverse effects of spaceflight begin at launch and continue throughout the duration of the mission, and in some cases, across the lifetime of the astronaut. Historically, research has been conducted in individual risk "silos" to characterize risk, however, astronauts are exposed to all risks simultaneously. In January of 2020, the HSRB at NASA began assessing the potential value of causal diagramming as a tool to facilitate understanding of the complex causes and effects that contribute to spaceflight-induced human system risk. Causal diagrams in the form of directed acyclic graphs (DAGs) are used to provide HSRB stakeholders with a shared mental model of the causal flow of risk. While primarily improving communication among those stakeholders, DAGs also allow a composite risk network to be created that can be tracked and configuration managed. This paper outlines the HSRB's pilot process for this effort, the lessons learned, and future goals for data-driven risk management approaches.

Levels of evidence for human system risk evaluation.

NASA uses a continuous risk management process to seek out new knowledge of spaceflight-induced risk to human health and performance. The evidence base that informs the risk assessments in this domain is constantly changing as more information is gleaned from a continuous human presence in space and from ongoing research. However, the limitations of this evidence are difficult to characterize because fewer than 700 humans have ever flown in space, and information comes from a variety of sources that span disciplines, including engineering, medicine, food and nutrition, and many other life sciences. The Human System Risk Board (HSRB) at NASA is responsible for assessing risk to astronauts and communicating this risk to agency decision-makers. A critical part of that communication is conveying the uncertainty regarding the understanding of the changes that spaceflight induces in human processes and the complex interactions between humans and the spacecraft. Although the strength of evidence grades is common in the academic literature, these scores are often not useful for the problems of human spaceflight. The HSRB continues to update the processes used to report the levels of evidence. This paper describes recent updates to the methods used to assign the level of evidence scores to the official risk postures and to the causal diagrams used by the HSRB.

Time-resolved molecular measurements reveal changes in astronauts during spaceflight.

From the early days of spaceflight to current missions, astronauts continue to be exposed to multiple hazards that affect human health, including low gravity, high radiation, isolation during long-duration missions, a closed environment and distance from Earth. Their effects can lead to adverse physiological changes and necessitate countermeasure development and/or longitudinal monitoring. A time-resolved analysis of biological signals can detect and better characterize potential adverse events during spaceflight, ideally preventing them and maintaining astronauts' wellness. Here we provide a time-resolved assessment of the impact of spaceflight on multiple astronauts (n = 27) by studying multiple biochemical and immune measurements before, during, and after long-duration orbital spaceflight. We reveal space-associated changes of astronauts' physiology on both the individual level and across astronauts, including associations with bone resorption and kidney function, as well as immune-system dysregulation.

Time-resolved molecular measurements reveal changes in astronauts during spaceflight.

From the early days of spaceflight to current missions, astronauts continue to be exposed to multiple hazards that affect human health, including low gravity, high radiation, isolation during long-duration missions, a closed environment and distance from Earth. Their effects can lead to adverse physiological changes and necessitate countermeasure development and/or longitudinal monitoring. A time-resolved analysis of biological signals can detect and better characterize potential adverse events during spaceflight, ideally preventing them and maintaining astronauts' wellness. Here we provide a time-resolved assessment of the impact of spaceflight on multiple astronauts (n=27) by studying multiple biochemical and immune measurements before, during, and after long-duration orbital spaceflight. We reveal space-associated changes of astronauts' physiology on both the individual level and across astronauts, including associations with bone resorption and kidney function, as well as immune-system dysregulation.

Modeling Occupational Fingernail Onycholysis Disorders in the Population of US Astronauts Who Have Engaged in Extravehicular Activity.

OBJECTIVES: Spacesuits are designed to be reliable personal spacecraft that preserve the life and well-being of the astronaut from the extremes of space. However, materials, operating pressures, and suit design requirements often result in a risk of musculoskeletal discomfort and injury to various areas of the body. In particular, this investigation looked at fingernails and their risk of developing onycholysis. METHODS: An onycholysis literature review was followed by a retrospective analysis of injury characteristics, astronaut suited training and spaceflight events, hand anthropometry, glove sizing, and astronaut demographics. Multiple logistic regression was used to assess the likelihood of onycholysis occurrence by testing potential risk variables against the dataset compiled from the retrospective data mining. RESULTS: The duration of event exposure, type of glove used, distance (delta) between the fingertip and the tip of the glove, sex, and age were found to be significantly related to occurrence of onycholysis (whether protective or injurious). CONCLUSION: An initial risk formula (model) for onycholysis was developed as a result of this investigation. In addition to validation through a future study, further improvement to this onycholysis equation and spacesuit discomfort and injury in general can be aided by future investigations that lead to better definition of the threshold between safe and risky exposure for each type of risk factor. APPLICATION: This work described a potential method that can be used for EVA spacesuit glove onycholysis injury risk analysis for either iterative glove design or between glove comparisons, such as during a product downselect process.

Long-term Cardiovascular Risk in Astronauts: Comparing NASA Mission Astronauts With a Healthy Cohort From the Cooper Center Longitudinal Study.

OBJECTIVE: To determine the long-term cardiovascular disease risk of astronauts with spaceflight exposure compared with a well-matched cohort. METHODS: National Aeronautics and Space Administration (NASA) astronauts are selected into their profession based upon education, unique skills, and health and are exposed to cardiovascular disease risk factors during spaceflight. The Cooper Center Longitudinal Study (CCLS) is a generally healthy cohort from a preventive medicine clinic in Dallas, Texas. Using a matched cohort design, astronauts who were selected beginning April 1, 1959, (and each subsequent selection class through 2009) and exposed to spaceflight were matched to CCLS participants who met astronaut selection criteria; 1514 CCLS participants matched to 303 astronauts in a 5-to-1 ratio on sex, date of birth, and age. The outcome of cardiovascular mortality through December 31, 2016, was determined by death certificate or National Death Index. RESULTS: There were 11 deaths caused by cardiovascular disease (CVD) among astronauts and 46 among CCLS participants. There was no evidence of increased mortality risk in astronauts (hazard ratio [HR]=1.10; 95% confidence interval [CI], 0.50 to 2.45) with adjustment for baseline cardiovascular covariates. However, the secondary outcome of CVD events showed an increased adjusted risk in astronauts (HR=2.41; 95% CI, 1.26 to 4.63). CONCLUSION: No increased risk of CVD mortality was observed in astronauts with spaceflight exposure compared with a well-matched cohort, but there was evidence of increased total CVD events. Given that the duration of spaceflight will increase, particularly on missions to Mars, continued surveillance and mitigation of CVD risk is needed to ensure the safety of those who venture into space.

Surveillance for jugular venous thrombosis in astronauts.

BACKGROUND: Thrombosis of the left internal jugular vein in an astronaut aboard the International Space Station was recently described, incidentally discovered during a research study of blood flow in neck veins in microgravity. Given this event, and the high incidence of flow abnormalities, the National Aeronautics and Space Administration (NASA) instituted an occupational surveillance program to evaluate astronauts for venous thrombosis. METHODS: Duplex ultrasound of the bilateral internal jugular veins was conducted on all NASA astronauts terrestrially, and at three points during spaceflight. Respiratory maneuvers were performed. Images were analyzed for thrombosis and certain hemodynamic characteristics, including peak velocity and degree of echogenicity. RESULTS: Eleven astronauts were evaluated with matching terrestrial and in-flight ultrasounds. No thrombosis was detected. Compared to terrestrial ultrasound measurements, in-flight peak velocity was reduced and lowest in the left. Six of 11 astronauts had mild-moderate echogenicity in the left internal jugular vein during spaceflight, but none had more than mild echogenicity in the right internal jugular vein. Two astronauts developed retrograde blood flow in the left internal jugular vein. CONCLUSION: Abnormal flow characteristics in microgravity, most prominent in the left internal jugular vein, may signal an increased risk for thrombus formation in some individuals.

Cancer incidence and mortality in the USA Astronaut Corps, 1959-2017.

OBJECTIVES: Cancer incidence and mortality are important outcomes in the surveillance of long-term astronaut health. We compare cancer incidence rates, cancer-specific mortality rates, and cancer case-fatality ratios in US astronauts with those in the US general population. METHODS: We use standardised incidence ratios (SIRs) and standardised mortality ratios (SMRs) to index the incidence and mortality of various cancers against rates in the US general population, from the US astronaut cohort inception in April 1959 through 31 December 2017. We compare the lethality of these cancers using the relative case-fatality ratio. RESULTS: Overall cancer incidence and mortality were slightly lower than expected from national rates with SIR 82 (95% CI 63 to 104) and SMR 72 (95% CI 44 to 111) with a modest 14% reduction in case-fatality ratio. Prostate cancer and melanoma skin cancer had significant increases in incidence, with SIR of 162 (95% CI 109 to 232) and 252 (95% CI 126 to 452), respectively, though only melanoma had a significant increase in mortality, with SMR 508 (95% CI 105 to 1485). Lung cancer had a significant deficit of both cases and deaths, while colon cancer had sizeable (but not significant) reductions in incidence and mortality. CONCLUSIONS: The increase in incidence of melanoma is consistent with that observed in aircraft pilots, suggesting this may be associated with ultraviolet radiation or lifestyle factors rather than any astronaut-specific exposure. Reductions in lung cancer incidence and mortality, and trends towards such reductions in colon cancer, may be explained in part by healthy lifestyle, as well as differential screening among astronauts.

Potential Venous Thromboembolism Risk in Female Astronauts.

BACKGROUND: Whether the unique environment of space affects astronaut risk of venous thromboembolism (VTE) is not known. On Earth, it is known that use of combined oral contraceptives (COCs) doubles the risk of VTE. Since some female astronauts choose to use COCs, this retrospective study examined known risk factors associated with VTE risk to determine whether the available data suggested elevated VTE risk in female astronauts.METHODS: Longitudinal health data were requested for female astronauts who flew short and long duration missions between 2000 and 2014. Pre- and postflight hematological and biochemical blood markers were available and evaluated. Astronauts' postflight measurements were compared to clinically relevant terrestrial high risk levels to determine any trend toward increased risk for VTE following spaceflight. Secondarily, a comparison of pre- and postflight changes was made, as well as an assessment of COC impact.RESULTS: A total of 38 astronaut-flights were included in this study and no VTE events were found. Analysis of potential VTE risk factors showed no evidence suggesting elevated VTE risk in female astronauts associated with spaceflight, regardless of contraceptive use.DISCUSSION: Arguably, all astronauts encounter many physiological stressors during spaceflight missions, but women using the combined contraceptive pill add a known risk factor for VTE. The risk factors analyzed within this study showed no trend toward an increased risk of VTE for female astronauts. This study provides an evidence base supporting the safety of COC use by female astronauts and also reinforces the importance of healthy lifestyle on VTE risk reduction.Jain V, Ploutz-Snyder R, Young M, Charvat JM, Wotring VE. Potential venous thromboembolism risk in female astronauts. Aerosp Med Hum Perform. 2020; 91(5):432-439.

Incidence Rate of Cardiovascular Disease End Points in the National Aeronautics and Space Administration Astronaut Corps.

BACKGROUND: It is unknown whether the astronaut occupation or exposure to microgravity influences the risk of long-term cardiovascular disease (CVD). This study explored the effects of being a career National Aeronautics and Space Administration (NASA) astronaut on the risk for clinical CVD end points. METHODS AND RESULTS: During the Longitudinal Study of Astronaut Health, data were collected on 310 NASA astronauts and 981 nonastronaut NASA employees. The nonastronauts were matched to the astronauts on age, sex, and body mass index, to evaluate acute and chronic morbidity and mortality. The primary outcomes were composites of clinical CVD end points (myocardial infarction, congestive heart failure, stroke, and coronary artery bypass surgery) or coronary artery disease (CAD) end points (myocardial infarction and coronary artery bypass surgery). Of the astronauts, 5.2% had a clinical CVD end point and 2.9% had a CAD end point compared with the nonastronaut comparisons with 4.7% and 3.1% having CVD and CAD end points, respectively. In the multivariate models adjusted for traditional risk factors, astronauts had a similar risk of CVD compared with nonastronauts (adjusted hazard ratio, 1.08; 95% CI, 0.60-1.93; P=0.80). Risk of a CAD end point was similar between groups (hazard ratio, 0.97; CI, 0.45-2.08; P=0.93). In astronauts with early spaceflight experience, the risk of CVD (hazard ratio, 0.80; CI, 0.25-2.56; P=0.71) and CAD (hazard ratio, 1.23; CI: 0.27-5.61; P=0.79) compared with astronauts with no experience were not different. CONCLUSIONS: These findings suggest that being an astronaut is not associated with increased long-term risk of CVD development.

Apollo Lunar Astronauts Show Higher Cardiovascular Disease Mortality: Possible Deep Space Radiation Effects on the Vascular Endothelium.

As multiple spacefaring nations contemplate extended manned missions to Mars and the Moon, health risks could be elevated as travel goes beyond the Earth's protective magnetosphere into the more intense deep space radiation environment. The primary purpose of this study was to determine whether mortality rates due to cardiovascular disease (CVD), cancer, accidents and all other causes of death differ in (1) astronauts who never flew orbital missions in space, (2) astronauts who flew only in low Earth orbit (LEO), and (3) Apollo lunar astronauts, the only humans to have traveled beyond Earth's magnetosphere. Results show there were no differences in CVD mortality rate between non-flight (9%) and LEO (11%) astronauts. However, the CVD mortality rate among Apollo lunar astronauts (43%) was 4-5 times higher than in non-flight and LEO astronauts. To test a possible mechanistic basis for these findings, a secondary purpose was to determine the long-term effects of simulated weightlessness and space-relevant total-body irradiation on vascular responsiveness in mice. The results demonstrate that space-relevant irradiation induces a sustained vascular endothelial cell dysfunction. Such impairment is known to lead to occlusive artery disease, and may be an important risk factor for CVD among astronauts exposed to deep space radiation.

Women's and men's exercise adherence after a cardiac event.

The purpose of this secondary analysis was to determine whether age affects women's and men's exercise adherence after a cardiac event. In a convenience sample of 248 adults ages 38 to 86 who had a cardiac event, exercise adherence (three exercise sessions per week) was compared between men and women in three age groups (younger than 60, 61 to 70, and older than 70). Exercise patterns were recorded by heart rate monitors worn during exercise. No differences were found in adherence between the age groups for women; older men were nonadherent sooner than younger men when controlling for fitness level, pain, comorbidity, self-efficacy, depressed mood, and social support. Exercise adherence after a cardiac event was higher for younger men compared with older men. For all age groups, less than 37% of the total sample adhered to a three-times-per-week exercise regimen after 1 year, suggesting that interventions to maintain exercise adherence are needed.

Promoting health behavior change using appreciative inquiry: moving from deficit models to affirmation models of care.

This article describes a new theoretical approach to health promotion and behavior change that may be especially suited to underserved women. Appreciative inquiry (AI), an organizational development process that focuses on the positive and creative as a force for an improved future, is described and adapted for use as an intervention to achieve health behavior change at the individual level. Guiding principles for its use with clients are provided, and an example of its application is illustrated in a hypothetical case study of an African American woman of low-socioeconomic resources who is attempting to increase lifestyle exercise following a cardiac event. AI is contrasted with the more traditional problem-solving approaches to the provision of care. The advantages, challenges, and issues associated with the use of AI as a health behavior change strategy are discussed.

Effects of a CHANGE intervention to increase exercise maintenance following cardiac events.

BACKGROUND: Despite participation in a cardiac rehabilitation program, there is a downward trajectory of exercise participation during the year following a cardiac event. PURPOSE: The purpose of this study was to test the effectiveness of CHANGE (Change Habits by Applying New Goals and Experiences), a lifestyle modification program designed to increase exercise maintenance in the year following a cardiac rehabilitation program. The CHANGE intervention consists of 5 small-group cognitive-behavioral change counseling sessions in which participants are taught self-efficacy enhancement, problem-solving skills, and relapse prevention strategies to address exercise maintenance problems. METHOD: Participants (N = 250) were randomly assigned to the CHANGE intervention (supplemental to usual care) or a usual-care-only group. Exercise was measured using portable wristwatch heart rate monitors worn during exercise for 1 year. Cox proportional hazards regression was used to determine differences in exercise over the study year between the study groups. RESULTS: Participants in the usual-care group were 76% more likely than those in the CHANGE group to stop exercising during the year following a cardiac rehabilitation program (hazard ratio = 1.76, 95% confidence interval = 1.08-2.86, p = .02) when adjusting for the significant covariates race, gender, comorbidity, muscle and joint pain, and baseline motivation. Most participants, however, had less than recommended levels of exercise amount and intensity. CONCLUSIONS: Counseling interventions that use contemporary behavior change strategies, such as the CHANGE intervention, can reduce the number of individuals who do not exercise following cardiac events.

Use of audio-enhanced personal digital assistants for school-based data collection.

PURPOSE: To review the different data collection options available to school-based researchers and to present the preliminary findings on the use of audio-enhanced personal digital assistants (APDA) for use in school-based data collection. METHODS: A newly developed APDA system was used to collect baseline data from a sample of 645 seventh grade students enrolled in a school-based intervention study. Evaluative measures included student response, time to completion, and data quality (e.g., missingness, internal consistency of responses). Differences in data administration and data quality were examined among three groups of students: students newer to the United States speaking English as a second language; special education students; and students not newer to the United States receiving regular education. RESULTS: The APDA system was well received by students and was shown to offer improvements in data administration (increased portability, time to completion) and reduced missing data. Although time to completion and proportion of missing data were similar across the three groups of students, psychometric properties of the data varied considerably. CONCLUSIONS: The APDA system offers a promising new method for collecting data in the middle school environment. Students with cognitive deficits and language barriers were able to complete the survey in a similar amount of time without additional help; however, differences in data quality suggest that limitations in comprehension of the questions remained even though the questions were read to the respondents. More research on the use of APDA is necessary to fully understand the effect of data collection mode with special populations.

Using the CHANGE intervention to enhance long-term exercise.

Although Phase II Cardiac Rehabilitation (CR) is effective at reconditioning people following cardiac events, it has had limited effectiveness in assisting participants to maintain the long-term exercise necessary for secondary prevention of cardiovascular events. This article describes a promising new intervention, CHANGE (Change Habits by Applying New Goals and Experiences), designed to enhance individuals' problem solving, self-efficacy, and relapse prevention skills regarding long-term exercise. Five small-group, nurse-led sessions are used to provide the intervention during the last three weeks of the formal CR program, and at one and two months following CR. Pilot data indicate that the CHANGE intervention has a positive effect on number and length of exercise sessions, number of minutes exercised, and time spent in target heart rate (HR) zone as measured by wristwatch HR monitors for three months following CR. The CHANGE intervention was found to be acceptable to clients and feasible to clinicians.