Effects of exercise countermeasures on multisystem function in long duration spaceflight astronauts.

Exercise training is a key countermeasure used to offset spaceflight-induced multisystem deconditioning. Here, we evaluated the effects of exercise countermeasures on multisystem function in a large cohort (N = 46) of astronauts on long-duration spaceflight missions. We found that during 178 ± 48 d of spaceflight, ~600 min/wk of aerobic and resistance exercise did not fully protect against multisystem deconditioning. However, substantial inter-individual heterogeneity in multisystem response was apparent with changes from pre to postflight ranging from -30% to +5%. We estimated that up to 17% of astronauts would experience performance-limiting deconditioning if current exercise countermeasures were used on future spaceflight missions. These findings support the need for refinement of current countermeasures, adjunct interventions, or enhanced requirements for preflight physiologic and functional capacity for the protection of astronaut health and performance during exploration missions to the moon and beyond.

Bisphosphonate Use May Reduce the Risk of Urolithiasis in Astronauts on Long-Term Spaceflights.

Long-duration spaceflight is associated with an increased risk of urolithiasis, and the pain caused by urinary calculi could result in loss of human performance and mission objectives. The present study investigated the risk of urolithiasis in astronauts during 6 months on the International Space Station, and evaluated whether the suppression of bone resorption by the bisphosphonate, alendronate (ALN), can reduce the risk. A total of 17 astronauts were included into the analysis: exercise using the advanced resistive exercise device (ARED) plus weekly oral 70 mg alendronate (ARED+ALN group, n = 7) was compared to resistive exercise alone (ARED group, n = 10). Urine volume decreased in both groups during spaceflight but recovered after return. The ARED group showed increased urinary calcium excretion from the 15th to 30th day of spaceflight, whereas urinary calcium was slightly decreased in the ARED+ALN group. Urinary N-terminal telopeptide (NTX) and helical peptide (HP) of type I collagen, as bone resorption markers, were elevated in the ARED group during and until 0 days after spaceflight, while there was no elevation in these parameters in the ARED+ALN group. Urinary oxalate and uric acid excretion tended to be higher in the ARED group than in the ARED+ALN group during spaceflight. These results demonstrate that astronauts on long-duration spaceflights may be at high risk for the formation of urinary calcium oxalate and calcium phosphate stones through increased urinary excretion of oxalate and uric acid, from degraded type I collagen, as well as of calcium from enhanced bone resorption. Our findings suggest that increased bone resorption during spaceflight, as a risk factor for urinary calculus formation, could be effectively prevented by an inhibitor of bone resorption. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Emotion Regulation in Elementary School-Aged Children with a Maternal History of Suicidal Behavior: A Pilot Study.

Parental history of suicidal behavior is associated with an increased risk of early onset suicidal behavior in their offspring. The objective of this pilot study was to compare clinical characteristics, temperament, and emotion regulation in children, aged 6-9 years, with (PH+) and without (PH-) a maternal history of suicidal behavior to determine which factors could be markers of early vulnerability. At baseline, PH+ children, compared to PH- children, demonstrated more difficulties with temperament, emotion regulation, and experienced more life events in the year prior to their baseline appointment. At study follow-ups, however, no differences were found between PH+ and PH- children. Results suggest there are some signals of early vulnerability present in children with a maternal history of suicidal behavior and recruitment/retention of this group of youth is feasible.

Use of Quantitative Computed Tomography to Assess for Clinically-relevant Skeletal Effects of Prolonged Spaceflight on Astronaut Hips.

INTRODUCTION: In 2010, experts in osteoporosis and bone densitometry were convened by the Space Life Sciences Directorate at NASA Johnson Space Center to identify a skeletal outcome in astronauts after spaceflight that would require a clinical response to address fracture risk. After reviewing astronaut data, experts expressed concern over discordant patterns in loss and recovery of bone mineral density (BMD) after spaceflight as monitored by dual-energy X-ray absorptiometry (DXA) and quantitative computed tomography (QCT). The pilot study described herein demonstrates the use of QCT to evaluate absence of recovery in hip trabecular BMD by QCT as an indicator of a clinically actionable response. METHODOLOGY: QCT and DXA scans of both hips were performed on 10 astronauts: once preflight and twice postflight about 1 wk and 1 yr after return. If trabecular BMD had not returned to baseline (i.e., within QCT measurement error) in 1 or both hips 1 yr after flight, then another QCT hip scan was obtained at 2 yr after flight. RESULTS: Areal BMD by DXA recovered in 9 of 10 astronauts at 1 yr postflight while incomplete recovery of trabecular BMD by QCT was evident in 5 of 10 astronauts and persisted in 4 of the 5 astronauts 2 yr postflight. CONCLUSION: As an adjunct to DXA, QCT is needed to detect changes to hip trabecular BMD after spaceflight and to confirm complete recovery. Incomplete recovery at 2 yr should trigger the need for further evaluation and possible intervention to mitigate premature fragility and fractures in astronauts following long-duration spaceflight.

Evaluating Bone Loss in ISS Astronauts.

INTRODUCTION: The measurement of bone mineral density (BMD) by dual-energy X-ray absorptiometry (DXA) is the Medical Assessment Test used at the NASA Johnson Space Center to evaluate whether prolonged exposure to spaceflight increases the risk for premature osteoporosis in International Space Station (ISS) astronauts. The DXA scans of crewmembers' BMD during the first decade of the ISS existence showed precipitous declines in BMD for the hip and spine after the typical 6-mo missions. However, a concern exists that skeletal integrity cannot be sufficiently assessed solely by DXA measurement of BMD. Consequently, use of relatively new research technologies is being proposed to NASA for risk surveillance and to enhance long-term management of skeletal health in long-duration astronauts. Sibonga JD, Spector ER, Johnston SL, Tarver WJ. Evaluating bone loss in ISS astronauts.

Skeletal effects of long-duration head-down bed rest.

INTRODUCTION: Skeletal unloading during spaceflight causes regional loss of bone mineral density (BMD), primarily in the spine and lower body regions. This loss of skeletal mass could adversely affect crew health during and after spaceflight and jeopardize mission success. Bed rest has long been used as a spaceflight analog to study the effects of disuse on many body systems, including the skeleton. This study was undertaken by the NASA Flight Analogs Project (FAP) to collect control data for upcoming countermeasure studies. METHODS: There were 13 subjects who participated in 42, 44, 49, 52, 60, or 90 d of continuous, head-down bed rest. DXA scans (dual-energy X-ray absorptiometry) were obtained before and after bed rest to measure changes in BMD of the whole body, lumbar spine, hip, heel, and wrist; the 90-d subjects were also scanned at the 60-d time point. Follow-up DXA scans were performed after 6 mo and 12 mo of reambulation to assess BMD recovery. RESULTS: BMD changes were consistent with earlier bed rest and spaceflight studies, with statistically significant losses averaging 1% per month in the hip, pelvis, and heel. Recovery data were also consistent with data obtained after spaceflight. Bone biomarker data are described, and support the findings of previous studies. Specifically, the process of normal bone remodeling is uncoupled: increased bone resorption with no concomitant change in bone formation. CONCLUSION: The FAP appears to be a valid test bed for skeletal disuse studies, and should provide a useful research platform for evaluating countermeasures to spaceflight-induced bone loss.