INTRODUCTION: Microgravity exposure unloads the skeleton. This increases urinary calcium excretion, which reflects both increased bone loss and kidney stone formation risk. We studied the probability that first morning void (FMV) urinary calcium (Uca) measurements would capture the highest Uca concentration in a day.METHODS: For 8 wk, three men and three women collected void-by-void 24-h urine samples weekly. Uca concentration was analyzed using a calcein-based system. Uca concentrations were ranked among all samples from each person. FMV and non-FMV (nFMV) Uca concentrations were compared with a Mann Whitney U-test. The probability that an FMV would capture the highest Uca concentration in a day was assessed.RESULTS: Among 377 voids collected, 46 were FMV and 331 were nFMV. Among all samples, the Uca concentration for FMV was significantly higher than nFMV (P < 0.0001). Out of the 46 FMVs, 24 were highest in Uca concentration for the corresponding 24-h period, giving a 52.2% probability that any given FMV would capture the highest Uca concentration in a day. The probability of measuring the highest Uca concentration from at least 1 d increased to 77.1%, and 89.1% when two or three FMVs were collected respectively.DISCUSSION: Acquiring 2–3 repeated FMVs provides a high likelihood of capturing the highest Uca from a day. This suggests repeated first morning void Uca concentrations could assess the risk of bone loss and kidney stone formation, which may provide ability for real-time implementation of countermeasure programs to prevent bone and renal complications in prolonged spaceflight.Thamer S, Buckey JC. First void urinary calcium for tracking bone loss and kidney stone risk in space. Aerosp Med Hum Perform. 2022; 93(7):546–550.

INTRODUCTION: The purpose of this study was to assess test-retest reliability of the Pieterse return to flight duty protocol for cabin crew to return to flight duties.METHOD: Flight attendants between 20–50 yr old were included if they underwent rehabilitation at the musculoskeletal rehabilitation unit for a musculoskeletal injury, surgical treatment for orthopedic trauma or industrial injuries, and were assessed by the treating physical therapist and aviation medical examiner to be ready for return to work. Test-retest reliability was calculated with the Fleiss kappa coefficient.RESULTS: Included were 18 flight attendants (10 men, 34.9 ± 6.3 yr; 8 women, 34.2 ± 3.4 yr). Eight participants were rehabilitated following upper extremity injury, eight following lower extremity, and two following both upper and lower extremity injury. Perfect test-retest reliability was observed for nine items; kappa values above 0.9 were observed for three items; one item had a kappa value above 0.8 and two items had a kappa value of 0.78. The results for all 15 items were highly significant, demonstrating that the Fleiss kappa coefficients were significantly different from zero. The kappa coefficient strength of agreement was almost perfect for 13 and substantial for the remaining 3 items. Overall test-retest reliability was 0.95.DISCUSSION: This study demonstrated almost perfect test-retest reliability for 13 items and substantial reliability for two items, with an overall test-retest reliability of 0.95 for a return to flight assessment for flight attendants. The Pieterse protocol is a reliable tool to establish return to work for cabin crew.Hohmann E, Tetsworth K, Pieterse R. The test-retest reliability of the Pieterse protocol return to flight assessment for cabin crew. Aerosp Med Hum Perform. 2022; 93(7):551–556.

BACKGROUND: Although multiple studies have documented the impact of insufficient sleep on soldier performance, most studies have done so using artificial measures of performance (e.g., tablet or simulator tests). The current study sought to test the relationship between sleep and soldier performance during infantry battle drill training, a more naturalistic measure of performance.METHODS: Subjects in the study were 15 junior Special Operations infantry soldiers. Soldiers wore an actigraph and reported their subjective sleep duration and quality prior to close quarter battle (CQB) drills. Experienced leaders monitored each iteration of the CQB exercise and recorded the number of errors committed.RESULTS: The number of errors committed during the live ammunition iterations was negatively correlated with subjective number of hours slept and subjective sleep efficiency/quality during the month prior. Soldiers with subjective sleep duration ≥7 h had a significantly lower number of errors than soldiers with subjective sleep duration <7 h (1.71 vs. 0.63 errors), and soldiers with sleep quality <85% committed more errors than those with sleep quality ≥85% (1.50 vs. 0.40 errors).DISCUSSION: These data preliminarily suggest that sleep quality and duration may influence subsequent performance on infantry battle drill training, particularly for soldiers with limited experience in battle drill conduction who have not yet perfected battle drill techniques. Future studies should enact sleep augmentation to determine the causal influence of sleep on performance in this setting.Mantua J, Shevchik JD, Chaudhury S, Eldringhoff HP, Mickelson CA, McKeon AB. Sleep and infantry battle drill performance in Special Operations soldiers. Aerosp Med Hum Perform. 2022; 93(7):557–561.

INTRODUCTION: Exposure to traumatic events could increase post-traumatic stress disorder (PTSD) risk among enlisted U.S. Army drone operators. Published research on PTSD risk in this population is unavailable.METHODS: We used a combined medical and administrative longitudinal dataset to examine adjusted associations between drone operator service among U.S. Army enlisted members and three PTSD indicators: whether screened via the PTSD Checklist – Civilian (PCL-C); PCL-C scores; and incident PTSD diagnoses. We compiled summary statistics for and conducted tests of differences in independent variable distributions when comparing drone operators and others. Two multivariable survival regression models and an ordinary least squares model were used to estimate adjusted associations.RESULTS: There were 1.68 million person-years of observed time in the study population (N = 678,548; drone operator N = 2856). Compared to other servicemembers, the adjusted likelihood of undergoing PTSD screening was 35% lower [95% confidence interval (CI) for the adjusted hazard ratio (aHR): 0.56–0.76]. Among subjects who took the PCL-C, scores did not differ significantly on the basis of drone operator service (adjusted change: −1.26 points; CI: −3.41–0.89). The adjusted hazard of receiving a PTSD diagnosis was 34% lower among drone operators (CI: 0.54–0.80).DISCUSSION: These findings provide reassurance that enlisted U.S. Army drone operators are not at increased risk of PTSD. Further research is needed in order to identify the mechanisms of the decreased PTSD risk observed, and whether other or longer-term mental health risks are present among those in this occupation.Nelson DA, Wilson M, Kurina LM. Post-traumatic stress disorder among U.S. Army drone operators. Aerosp Med Hum Perform. 2022; 93(7):562–570.

BACKGROUND: The practice of self-medication among military fighter aircrew could compromise flight safety because of the adverse effects that can occur in flight. However, data on this subject is scarce. The aim of this study was to identify the determinants of the practice in this population.METHODS: A cross-sectional study was carried out among the French Air Force fighter aircrew based on an anonymous questionnaire distributed electronically. The questions included personal characteristics, opinions, and relations with the healthcare domain as well as the use of self-medication in general and before a flight.RESULTS: Between March and November 2020, 170 questionnaires were reviewed for an overall return rate of approximately 34%. Our data showed an absolute self-medication rate of 97.6%, but the frequency of its use was rare or nonexistent in 53.5% of cases. Factors associated with a more frequent use of self-medication were the function of pilot, age under 35, having a regular prescription, lacking intentionality toward getting enough sleep, having confidence in the medical profession, and some specific clinical situations. The consumption of 97 medications was recorded and 49 before a flight.DISCUSSION: Despite the limitations due to the design of this survey, results suggest that the use of self-medication in fighter aircrews is a reality, but that the frequency of its use is less common. This practice is probably the result of a complex interaction between many personal factors. However, its impact on flight safety remains uncertain.du Baret de Limé M, Monin J, Leschiera J, Duquet J, Manen O, Chiniard T. Self-medication among military fighter aircrews. Aerosp Med Hum Perform. 2022; 93(7):571–580.

BACKGROUND: Optimal human performance and health is dependent on steady blood supply to the brain. Hypergravity (+G_z) may impair cerebral blood flow (CBF), and several investigators have also reported that microgravity (0 G) may influence cerebral hemodynamics. This has led to concerns for safe performance during acceleration maneuvers in aviation or the impact long-duration spaceflights may have on astronaut health.METHODS: A systematic PEO (Population, Exposure, Outcome) search was done in PubMed and Web of Science, addressing studies on how elevated +G_z forces or absence of such may impact cerebral hemodynamics. All primary research containing anatomical or physiological data on relevant intracranial parameters were included. Quality of the evidence was analyzed using the GRADE tool.RESULTS: The search revealed 92 eligible articles. It is evident that impaired CBF during +G_z acceleration remains an important challenge in aviation, but there are significant variations in individual tolerance. The reports on cerebral hemodynamics during weightlessness are inconsistent, but published data indicate that adaptation to sustained microgravity is also characterized by significant variations among individuals.DISCUSSION: Despite a high number of publications, the quality of evidence is limited due to observational study design, too few included subjects, and methodological challenges. Clinical consequences of high +G_z exposure are well described, but there are significant gaps in knowledge regarding the intracranial pathophysiology and individual hemodynamic tolerance to both hypergravity and microgravity environments.Saehle T. Cerebral hemodynamics during exposure to hypergravity (+G_z) or microgravity (0 G). Aerosp Med Hum Perform. 2022; 93(7):581–592.

INTRODUCTION: Israel began vaccinating with the booster dose of the Pfizer-BioNTech vaccine in July 2021, before the Food and Drug Administration (FDA) authorized the vaccine in September 2021. The first and second vaccines were shown to have several side effects that could possibly affect aircrews’ fitness to fly. Thus, the Israel Air Force (IAF) decided on a disqualification period of 24 h following the first vaccine, and 48 h following the second vaccine. The aim of this study was to determine the disqualification period following the booster dose of the vaccine.METHODS: A survey was conducted among IAF aviators in the Aeromedical Center (AMC) in order to characterize the side effects and their duration following a Pfizer-BioNTech COVID-19 vaccine booster dose.RESULTS: The most common local side effect was injection site pain. The most common systemic side effects were general weakness, fatigue, and myalgia. Duration of side effects was up to 48 h from vaccine administration among the majority of aircrew members.CONCLUSION: The IAF AMC policy for the Pfizer-BioNTech COVID-19 vaccine booster dose recipients is to disqualify from flight for 48 h following the vaccination.Ekshtein A, Hay G, Shapira S, Ben-Ari O. Return to flying duties following a COVID-19 booster dose. Aerosp Med Hum Perform. 2022; 93(7):593–596.

BACKGROUND: Accidents during start-up and shut-down procedures of aircraft can lead to fatalities or destroyed aircraft. Start-up procedures for propeller aircraft include the possibility of hand-propping, which may increase the occurrence of injuries from propeller strikes.METHODS: A set of 142 accidents from a 10-yr period were selected from the U.S. National Transportation Safety Board online database. Only fixed-wing aircraft in the “standing” phase of flight were included in the dataset. The significance of differences was determined using Pearson’s Chi-squared analysis.RESULTS: The severity of the injuries sustained in the accidents were inversely related to the amount of damage to the aircraft. Hand-propping without properly securing the aircraft was more likely to result in substantial damage to the aircraft. Pilots with less than a thousand hours of flight experience were significantly more likely to use an incorrect hand-propping procedure.CONCLUSIONS: It is recommended to make the advisory on hand-propping a regulatory article of the Federal Aviation Administration so that pilots’ knowledge of this procedure is mandatory and part of their initial training, especially securing the aircraft during hand-propping. Highlighting throttle positions in both regular and hand-propping procedures may optimize checklist design and further mitigate accidents during start-up procedures.de Voogt AJ, Kalagher H, Burns S. General aviation accidents involving fixed-wing aircraft on the ground. Aerosp Med Hum Perform. 2022; 93(7):597–600.