Energy Expenditure and Changes in Body Composition during Submarine Deployment-An Observational Study "DasBoost 2-2017"

Navigating the Depths of Cardiovascular Effects on Submariners

The environment of the submariner is inherently endowed with several health risk factors, namely confinement, inactivity, caloric excess, and circadian disruption, among others, during deployment. Metabolic disturbances, increased cardiovascular risk, and sleep deprivation are associated with interrupting circadian rhythms due to routines contributing to physiological and cognitive abnormalities. Additionally, submariners face vitamin deficits of vitamin D and vitamin B12 due to little exposure to sunlight and poor nutrition. It is associated with cardiovascular dysfunctions, endothelial dysfunctions, metabolic abnormalities, and a greater cardiovascular risk. Moreover, high obesity prevalence has been noted among submariners. Such cases were attributed to leptin resistance, body fat deposits, and lifestyle statistics. Other risk factors to the cardiovascular system, like changes in heart rate variability and heart functions, have been witnessed. These health challenges can be mitigated by adopting proactive steps to address submariners' specific health needs. Such measures should include the prevention of stable circadian rhythms, vitamin intake, lifestyle, and cardiovascular health. By addressing these issues, submariners' well-being will be upheld, and their vulnerability to cardiovascular diseases and other health-related complications will be lessened.

The sleep, circadian, and cognitive performance consequences of watchkeeping schedules in submariners: A scoping review

Watchkeeping schedules are essential for maintaining submarine operations, but come with human risk factors including, disrupted sleep, circadian misalignment, and cognitive deficits. There is now an emerging literature examining the strengths and weaknesses of submarine watchkeeping schedules trialled in the field and under simulated laboratory conditions. The aim of this scoping review was to summarise this literature. A systematic search of peer-reviewed journal articles and industry reports listed in MEDLINE, PsychINFO, PubMed, Scopus, Embase and Google Scholar undertaken in May 2023 returned 7298 papers. Following screening procedures, 13 studies were identified for inclusion. The findings revealed that sleep was sufficiently preserved regardless of watchkeeping schedule (total sleep time = 5.46-7.89 h), circadian misalignment was greater for non-24 h schedules, and longer off-watch periods were associated with better cognitive performance. Taken together, when comparing between watchkeeping schedules, the present findings suggest that the 4 h-on/8 h-off and 8 h-on/16 h-off schedules may be a good compromise when balancing human risk factors and operational demands. However, submarines are complex and challenging environments to study and there is a need to expand the literature. More research comparing watchkeeping schedules is needed. Future studies should focus on cognitive performance measures, such as problem-solving, prioritisation and executive decision-making to address present shortcomings, and an examination of sleep and circadian countermeasures to assist with adaptation either initiated pre-deployment or by modifying the submarine environment itself should be considered.

Vitamin D status in active duty Navy military personnel: a systematic review

OBJECTIVES

Active duty Navy military personnel are prone to vitamin D deficiency due to an occupational environment detrimental to sunlight exposure. The main objective of this systematic review is to provide a worldwide overview of vitamin D status in this population.

METHODS

The Condition, Context, Population (CoCoPop) mnemonic was used to define the inclusion criteria (vitamin D status; all contexts; active duty Navy military personnel). Studies with recruits or veterans were excluded. Scopus, Web of Science and PubMed/Medline databases were searched from inception to 30 June 2022. Joanna Briggs Institute and Downs & Black checklists were used for quality assessment and data were synthesised in narrative and tabular formats.

RESULTS

Thirteen studies published between 1975 and 2022 and conducted in northern hemisphere Navies, including mainly young and male service members, were included. The prevalence of vitamin D deficiency was globally reported as significant. Nine studies included a total of 305 male submariners who performed 30-92 days submarine patrol and reported the effect of sunlight deprivation in the decrease of vitamin D levels.

CONCLUSIONS

This new systematic review underlines the high prevalence of vitamin D deficiency in the Navy, especially in submariners, and the need to implement measures to prevent vitamin D deficiency. Serum 25(OH)D data available and the heterogeneity of the studies limited a pooled analysis. Most studies included only submariners, which may limit generalisability to all active duty Navy military personnel. Further research on this topic should be promoted.

PROSPERO REGISTRATION NUMBER

CRD42022287057.

Vitamin D status in the active duty Navy military personnel: protocol for a systematic review

INTRODUCTION

Vitamin D is critical for bone health and its deficiency has been linked to increased incidence and severity of multiple diseases. Even so, vitamin D inadequacy is a major public health problem worldwide. The main source of vitamin D is endogenous cutaneous synthesis through exposure to solar ultraviolet B radiation, which is influenced by several factors, including occupational. The active duty Navy military personnel may be prone to vitamin D inadequacy, but a worldwide overview of vitamin D status in this specific population is still lacking.

METHODS AND ANALYSIS

The CoCoPop mnemonic will be used for determining the inclusion criteria. Scopus, Web of Science and PubMed/Medline will be searched for all studies including 25-hydroxyvitamin D concentrations of the active duty Navy military personnel. Data extraction and quality assessment (Joanna Briggs Institute's and Downs and Black checklists) will be performed by two reviewers and data will be synthesised in narrative, tabular and map formats.

ETHICS AND DISSEMINATION

This study will not involve human or animal subjects and, thus, does not require ethics approval. The outcomes will be disseminated via publication in a peer-reviewed scientific journal and presentation at a scientific conference.

PROSPERO REGISTRATION NUMBER

CRD42022287057.

Comparison of Energy and Nutrient Intake vs. Estimated Needs in Warfighters: an Update

Active members of the military must perform optimally under conditions of thermal stress and/or energy deficiency. Military dietary reference intakes (MDRIs) provide guidelines for energy and nutrient intakes but is based studies largely conducted in Army. Needs may vary by service branch and/or position. New protein recommendations have emerged, which are not reflected in MDRIs. PURPOSE OF REVIEW: Compare reported dietary intake in active duty members to MDRIs and 2016 American College of Sports Medicine (ACSM) sports nutrition guidelines. RECENT FINDINGS: Active duty members are not meeting their energy and carbohydrate needs with low-to-adequate protein intake and adequate-to-high fat intake. Other nutrients of concern are vitamin D, calcium, iron, B-vitamins, and fiber. Thermal stress increases energy needs and suppresses appetite and thus increase risk for energy and nutrition deficiencies. Energy and nutrients needs can vary by branch of armed service, job responsibility, and external stressors.

Energy Deficiency in Soldiers: The Risk of the Athlete Triad and Relative Energy Deficiency in Sport Syndromes in the Military

Military personnel experience energy deficit (total energy expenditure higher than energy intake), particularly during combat training and field exercises where exercising energy expenditures are high and energy intake is reduced. Low energy availability (energy intake minus exercising energy expenditure expressed relative to fat free mass) impairs endocrine function and bone health, as recognized in female athletes as the Female Athlete Triad syndrome. More recently, the Relative Energy Deficiency in Sport (RED-S) syndrome encompasses broader health outcomes, physical and cognitive performance, non-athletes, and men. This review summarizes the evidence for the effect of low energy availability and energy deficiency in military training and operations on health and performance outcomes. Energy availability is difficult to measure in free-living individuals but doubly labeled water studies demonstrate high total energy expenditures during military training; studies that have concurrently measured energy intake, or measured body composition changes with DXA, suggest severe and/or prolonged energy deficits. Military training in energy deficit disturbs endocrine and metabolic function, menstrual function, bone health, immune function, gastrointestinal health, iron status, mood, and physical and cognitive performance. There are more data for men than women, and little evidence on the chronic effects of repeated exposures to energy deficit. Military training impairs indices of health and performance, indicative of the Triad and RED-S, but the multi-stressor environment makes it difficult to isolate the independent effects of energy deficiency. Studies supplementing with energy to attenuate the energy deficit suggest an independent effect of energy deficiency in the disturbances to metabolic, endocrine and immune function, and physical performance, but randomized controlled trials are lacking.