INTRODUCTION: The effects of low-grade hypoxia on cognitive function are reported in this paper. The study compared cognitive function during short exposures at four different altitudes.METHODS: Ninety-one subjects were exposed to simulated altitudes of ground level, 1524, 2438, and 3658 m (5000, 8000, and 12,000 ft) in the Brooks City-Base altitude pressure chamber in a balanced design. Oxygen saturation, heart rate, and cognitive performance on seven different cognitive tasks were measured. In addition, subjects indicated their symptoms from a 33-item subjective symptom survey.RESULTS: As designed, oxygen saturation decreased and heart rate increased with higher altitudes. Very small degradations in performance were found at the two highest altitudes for only two of the cognitive tasks (continuous performance and grammatical reasoning). In the subjective symptom survey, 18 of the 33 possible symptoms were more common at 3658 m (12,000 ft) than at ground level.CONCLUSIONS: The findings indicated a minimal influence of low-grade hypoxia on cognitive performance in contrast to some existing classic symptoms of hypoxia.Pilmanis AA, Balldin UI, Fischer JR. Cognition effects of low-grade hypoxia. Aerosp Med Hum Perform. 2016; 87(7):596–603.

BACKGROUND: Interactions between frequency and amplitude of latency in head-mounted displays (HMDs) are thought to affect simulator sickness. Many studies have linked system latency to subjective sickness, but recent research has found that at least with the case of inertia-based head tracking technology, latency is not a constant; rather it varies systematically over time due to sensor errors and clock asynchronization. The purpose of this experiment was to further explore the relationship between frequency and amplitude of latency as they relate to subjective sickness experienced in an HMD.METHODS: In a 2 (frequency) × 2 (amplitude) design, 120 subjects were randomly assigned to 4 latency conditions. Frequency of latency was either 0.2 Hz or 1.0 Hz. Amplitude of latency was either 100 ms fixed or 20-100 ms varying.RESULTS: A main effect of frequency of latency was found. Subjects reported greater sickness in the 0.2-Hz frequency conditions (39.0 ± 27.8) compared to the 1-Hz conditions (30.3 ± 17.0). Additionally, 18 subjects withdrew their participation early in the 0.2-Hz conditions compared to 7 in the 1.0-Hz conditions.DISCUSSION: In conclusion, frequency of latency appears to play a role in the experience of sickness in HMDs in both subjective reporting of symptoms and subject performance. The current study confirms results of earlier studies, finding that real motion around a frequency of 0.2 Hz is more sickening than other frequencies. Future work should continue to parse the effects of frequency and amplitude of latency in head-tracked HMDs.Kinsella A, Mattfeld R, Muth E, Hoover A. Frequency, not amplitude, of latency affects subjective sickness in a head-mounted display. Aerosp Med Hum Perform. 2016; 87(7):604–609.

INTRODUCTION: This study examined the effects of long-term bed rest with or without a concurrent resistance exercise protocol on different muscle function indices of the knee extensors and their influence on previously shown atrophy, neural impairment, and slow-to-fast phenotype shift.METHODS: Nine men underwent 90 d of bed rest only (BR), while eight men in addition performed maximal supine squats every third day (BRE). Before and at day 1 and 5 following bed rest, surface quadriceps electromyographic (EMG) activity was measured during a sustained (60-s) submaximal isometric action and rate of force development (RFD) was assessed during a maximal isometric action, both in the supine squat position. Maximal torque was measured during isokinetic knee extensions at different angular velocities before and after (day 2 and 11) bed rest.RESULTS: EMG amplitude at a fixed submaximal load increased in BR, but not in BRE. The increase in amplitude during the sustained action was elevated in BR but not in BRE. RFD decreased in BR; this effect was attenuated day 1 and normalized day 5 in BRE. RFD expressed relative to maximal force was maintained in both groups. Angle-specific torque decreased equally for all velocities in BR. The decrease in isokinetic strength was attenuated day 2 in BRE.DISCUSSION: Phenotype changes were not reflected in muscle function measurements, probably because they were overridden by the effects of atrophy and neural adaptation. The protective effect of resistance exercise was more pronounced in tasks similar to the training action, inferring great impact of neural mechanisms.Alkner BA, Norrbrand L, Tesch PA. Neuromuscular adaptations following 90 days bed rest with or without resistance exercise. Aerosp Med Hum Perform. 2016; 87(7):610–617.

BACKGROUND: Since 2004, in the United States, light sport aircraft (LSA) and some aircraft with standard airworthiness certificates can be operated for recreational purposes with a valid state driver’s license rather than a Federal Aviation Administration (FAA)-issued aeromedical certificate. There have been recent efforts to allow operation of much larger, heavier, faster, and more complex aircraft without requiring a medical certificate. The primary objective of this research was to compare hazards to flight safety identified in fatally injured pilots required to possess a valid FAA third-class medical certificate to hazards in fatally injured pilots who were not required to possess a valid medical certificate.METHODS: A search of all fatal U.S. aircraft accidents in the FAA Medical ANalysis and TRAcking (MANTRA) registry between January 1, 2011, and April 30, 2014, identified 1084 individuals. A review of accident pilots’ medical, autopsy, and toxicological data was conducted. After applying exclusion criteria, 467 pilots remained, including 403 medically certified and 64 medically uncertified pilots.RESULTS: A significant difference was found in a surrogate measure for risk between medically certified and uncertified pilots (25% vs. 59%). This difference remained significant after adjustment for age. No significant difference was found in the proportions of hazards identified on toxicological review.CONCLUSION: The results of this study suggest that the risk of an adverse medical event is reduced in pilots required to possess a valid medical certificate.Ricaurte EM, Mills WD, DeJohn CA, Laverde-Lopez MC, Porras-Sanchez DF. Aeromedical hazard comparison of FAA medically certified third-class and medically uncertified pilots. Aerosp Med Hum Perform. 2016; 87(7):618–621.

INTRODUCTION: Bilastine is a new oral, second generation antihistamine used in the symptomatic treatment of allergic rhinoconjunctivitis and urticaria. It is considered a nonsedating antihistamine and might be recommended for use in pilots, pending research on the effects on flying-related performance under hypobaric conditions that prevail in an airliner. We assessed the effects of a single dose of bilastine 20 mg on alertness and complex task performance of healthy volunteers in a hypobaric chamber at 75.2 kPa (8000 ft/2438 m cabin altitude).METHODS: In a randomized, double-blind, crossover study, 24 volunteers received a single dose of bilastine 20 mg, hydroxyzine 50 mg (active control), and placebo. Using the Vigilance and Tracking Task, Multi-Attribute Task Battery, and Stanford Sleepiness Scale, assessments were made before and up to 6 h after intake of the study medication.RESULTS: Bilastine 20 mg had no impairing effects on sleepiness levels, vigilance, or complex task performance for up to 6 h post-dose. Hydroxyzine 50 mg (active control) was associated with significant sleepiness and impaired performance across this time period, confirming the sensitivity of the tests.CONCLUSION: Bilastine 20 mg did not cause sleepiness or impaired performance on tasks related to flying. It is anticipated that a single dose of bilastine 20 mg will not affect flying performance. Bilastine may provide a safe therapeutic alternative for pilots suffering from allergic rhinitis or urticaria. Our findings might also have implications for the treatment of allergic disorders of personnel involved in other safety-sensitive jobs.Valk PJL, Simons R, Jetten AM, Valiente R, Labeaga L. Cognitive performance effects of bilastine 20 mg during 6 hours at 8000 ft cabin altitude. Aerosp Med Hum Perform. 2016; 87(7):622–627.

BACKGROUND: Dietary supplement (DS) use is common among U.S. Army personnel to purportedly improve health, provide energy, and increase strength. However, a comprehensive analysis of DS use among U.S. Air Force (USAF) personnel has not been conducted using the same survey instrument, which would permit direct comparisons to DS use by Army personnel.METHODS: A standardized questionnaire was used to assess DS use, demographic factors, and reasons for use of DS by USAF personnel (N = 1750). Logistic regression models adjusted for age, sex, and rank were used to determine relationships among categories of DS (multivitamin and multimineral, individual vitamins and minerals, protein/amino acid supplements, combination products, herbal supplements, purported steroid analogs, and other) and demographic factors. Findings were compared to reports from other military services and civilian populations.RESULTS: DS were used by 68% of USAF personnel: 35% used 1–2 DS ≥ 1 time/wk, 13% 3–4 DS ≥ 1 time/wk, and 20% ≥ 5 DS ≥ 1 time/wk. There were 45% of personnel who used a multivitamin and mineral, 33% protein supplements, 22% individual vitamins/minerals, 22% combination products, and 7% herbals. Logistic regression demonstrated aerobic exercise duration and strength training were associated with increased DS use. Individuals who previously deployed were more likely to use DS.CONCLUSIONS: Like Army personnel, college students and athletes, USAF personnel use more DS than the general population and are more likely to use purported performance enhancing DS, such as protein supplements, and concurrently consume multiple DS.Austin KG, Price LL, McGraw SM, Leahy G, Lieberman HR. Demographic, lifestyle factors, and reasons for use of dietary supplements by Air Force personnel. Aerosp Med Hum Perform. 2016; 87(7):628–637.

BACKGROUND: Flight attendants (FAs) may experience circadian disruption due to travel during normal sleep hours and through multiple time zones. This study investigated whether FAs are at higher risk for sleep disturbance compared to teachers, as assessed by questionnaire, diary, and activity monitors.METHODS: Sleep/wake cycles of 45 FAs and 25 teachers were studied. For one menstrual cycle, participants wore an activity monitor and kept a daily diary. Sleep metrics included total sleep in the main sleep period (MSP), sleep efficiency (proportion of MSP spent sleeping), and nocturnal sleep fraction (proportion of sleep between 10 p.m. to 8 a.m. home time). Relationships between sleep metrics and occupation were analyzed with mixed and generalized linear models.RESULTS: Both actigraph and diary data suggest that FAs sleep longer than teachers. However, several actigraph indices of sleep disturbance indicated that FAs incurred significant impairment of sleep compared to teachers. FAs were more likely than teachers to have poor sleep efficiency [adjusted odds ratio (OR) for lowest quartile of sleep efficiency = 1.9, 95% Confidence Interval (CI) 1.2 – 3.0] and to have a smaller proportion of their sleep between 10 p.m. and 8 a.m. home time (adjusted OR for lowest quartile of nocturnal sleep fraction = 3.1, CI 1.1 -9.0).DISCUSSION: Study FAs experienced increased sleep disturbance compared to teachers, which may indicate circadian disruption.Grajewski B, Whelan EA, Nguyen MM, Kwan L, Cole RJ. Sleep disturbance in female flight attendants and teachers. Aerosp Med Hum Perform. 2016; 87(7)638–645.

INTRODUCTION: The recent developments of technology in almost all areas of industrial processing, workplace, smart homes, mobility, media, and communication change humans’ everyday life environment and behavioral responses in numerous ways. Our main objective in this study was to determine whether subjects’ operator performance in a complex sensorimotor task is associated with their gaze behavior.METHODS: In two experiments subjects operated a complex control task. To this end they watched multiple displays, made strategic decisions, and used multiple actuators to maximize their virtual earnings from operating a virtual power plant. In Experiment 1 we compared gaze behavior during the tasks with respect to operator performance in two different age groups (young vs. old), and in Experiment 2 in two different gravity conditions (normal vs. microgravity).RESULTS: We found gaze pattern changed in older subjects as well as in microgravity. Older adults and subjects in microgravity looked longer at areas that are less relevant for task success. Most importantly, these changes in gaze pattern accounted for the effects of age and microgravity and on total earnings in the instrument-control task.DISCUSSION: In conclusion, age- and gravity-related changes of gaze behavior show a similar pattern. Gaze behavior seems to play an important role in complex control tasks and might predict alterations of operational performance.Kalicinski M, Steinberg F, Dalecki M, Bock O. Gaze behavior while operating a complex instrument control task. Aerosp Med Hum Perform. 2016; 87(7):646–651.

BACKGROUND: The issue of expanding flight privileges that do not require medical oversight is currently an important topic, especially in the United States. We compared personal flying accident rates in aircraft with special light sport aircraft (SLSA) and experimental light sport aircraft (ELSA) airworthiness certificates to accident rates for personal flying in other general aviation (GA) aircraft.METHODS: To calculate accident rates, personal flying hours were obtained from the annual FAA General Aviation and Part 135 Activity Surveys, and numbers of personal flying accidents were obtained from the NTSB accident database. Overall and fatal personal flying accident rates for the SLSA and ELSA groups and other GA aircraft were calculated and accident rates were compared.RESULTS: The overall personal flying accident rate for SLSA and ELSA was found to be 29.8 per 100,000 flight hours and the fatal accident rate was 5.2 per 100,000 flying hours. These are both significantly greater than the overall personal flying rate of 12.7 per 100,000 h and fatal rate of 2.6 per 100,000 h for other GA aircraft.DISCUSSION: Although this study has several limitations, the significantly higher accident rates in the sport pilot aircraft suggests caution when expanding sport pilot privileges to include larger, more complex aircraft.Mills WD, DeJohn CA. Personal flying accident rates of selected light sport aircraft compared with general aviation aircraft. Aerosp Med Hum Perform. 2016; 87(7):652–654.

BACKGROUND: Centrifuge training, while an integral component in pilot training, is not without risks. To date there has never been a reported case of isolated transverse process fractures associated with centrifuge training.CASE REPORT: A 32-yr-old Flight Surgeon underwent centrifuge training as part of an educational course. She had increasing back pain after exposure to the centrifuge. Follow-up studies showed left L2 and bilateral L3 transverse process fractures. No other contributory causes could be identified except for mild vitamin D deficiency.DISCUSSION: The etiology, incidence, and treatment of transverse process fractures are examined to better prepare the clinician for the management of these cases.Puderbaugh MA. A report of transverse process fractures secondary to the centrifuge in a healthy aviator. Aerosp Med Hum Perform. 2016; 87(7):655–658.

Since the tragic accident of Germanwings flight 4U9525, there has been discussion about methods to identify and prevent suicidality in pilots. Neurogenetic scientists claim that biomarker tests for suicidality as part of healthcare assessments may lead to early identification of suicidal behavior. In this commentary the value of these gene expression biomarkers for aeromedical purposes is evaluated based on relevant literature. It is concluded that the currently identified biomarkers for suicidality need thorough validation before they can be used. The aeromedical examiner’s most important tool is still an anamnesis, in which warning signs of suicidal behavior can be picked up.Simons R. Use of gene expression biomarkers to predict suicidality. Aerosp Med Hum Perform. 2016; 87(7):659–660.

Rojas J. You’re the flight surgeon: F-16 pilot with papular rash. Aerosp Med Hum Perform. 2016; 87(7):661–663.