Impact of night sentry duties on cardiometabolic health in military personnel

Abstract

This article examines the study by Lin et al, which explores the effects of night sentry duties on cardiometabolic health in military personnel. The research identifies significant correlations between the frequency of night shifts and negative cardiometabolic outcomes, such as elevated resting pulse rates and lowered levels of high-density lipoprotein cholesterol. These outcomes underscore the health risks linked to partial sleep deprivation, a common challenge in military environments. The editorial highlights the clinical significance of these findings, advocating for the implementation of targeted health interventions to mitigate these risks. Strategies such as structured sleep recovery programs and lifestyle modifications are recommended to improve the health management of military personnel engaged in nocturnal duties. By addressing these issues, military health management can better safeguard the well-being and operational readiness of its personnel.

Key Words: Nocturnal duty; Cardiometabolic health; Military personnel; Sleep deprivation; Resting pulse rate; High-density lipoprotein cholesterol; Metabolic syndrome

Core Tip: This article highlights the significant impact of nocturnal sentry duties on cardiometabolic health, as demonstrated by Lin et al’s study. The findings underscore the importance of addressing the health risks associated with partial sleep deprivation in military personnel. Implementing interventions such as sleep recovery programs and promoting healthy lifestyle choices are essential strategies to enhance the well-being and operational readiness of individuals engaged in night shifts. The article calls for a comprehensive approach to health management that integrates biomarker analysis and lifestyle interventions to mitigate the adverse effects of night duties.

INTRODUCTION

Insufficient sleep, especially partial sleep deprivation due to night duties, presents significant health risks due to its extensive impact on physical and mental health[1]. This condition arises from a lack of necessary sleep quality or duration, crucial for maintaining optimal health and cognitive functions. Partial sleep deprivation is defined as short-term interruptions in sleep, typically lasting 2-3 hours, and occurring less than twice a week[2]. In the military, personnel often engage in night watch duties, disrupting their natural sleep cycles and potentially leading to several health issues. While previous research[2-4] has established connections between sleep deprivation and negative health outcomes like obesity, diabetes, and cardiovascular problems, there is a lack of focus on partial sleep deprivation, which is particularly relevant to military environments.

The recent study by Lin et al[5] meticulously examines the intricate relationship between nocturnal sentry duty and cardiometabolic characteristics among armed forces personnel. This observational study involved 867 military personnel aged 18-39, who were subjected to varying frequencies of night sentry duties. The primary aim was to elucidate the latent effects of partial sleep deprivation induced by night duties on cardiometabolic alterations.

The study by Lin et al[5] is pivotal as it sheds light on the effects of partial sleep deprivation, which is common in military settings, thereby filling a significant gap in existing literature. Investigating the impact of night duties on cardiometabolic health is vital, especially considering the prevalence of metabolic issues and obesity in military groups[6-10]. Such understanding is crucial for crafting interventions that mitigate health risks associated with disrupted sleep patterns among armed forces. By examining how the frequency of night duties affects cardiometabolic markers like heart rate and high-density lipoprotein cholesterol (HDL-C), the study offers crucial insights into the health implications of partial sleep deprivation[5].

The study by Lin et al[5], By examining how the frequency of night duties affects cardiometabolic markers like heart rate and HDL-C, the study offers crucial insights into the health implications of partial sleep deprivation. These findings highlight the need for addressing sleep deprivation within military health strategies to improve the well-being and operational readiness of personnel. The study also emphasizes the necessity for customized health interventions, considering the unique stressors and physical demands faced by this population.

THEORETICAL BACKGROUND: SLEEP DEPRIVATION AND ANXIETY

Chronic sleep deprivation is widely recognized as a significant contributor to various mental health issues, with substantial effects on cognitive functions and emotional regulation[11]. Insufficient sleep impairs the brain’s ability to process and consolidate information, resulting in notable deficiencies in attention, working memory, and executive functions, which are critical for everyday decision-making and problem-solving[12]. Furthermore, prolonged sleep loss has been linked to the onset of psychotic episodes, marked by hallucinations and delusions, particularly in individuals with pre-existing vulnerabilities to psychiatric disorders[13]. The dysregulation of neurotransmitter systems, including serotonin and dopamine, due to inadequate sleep, can intensify symptoms of anxiety and depression, leading to heightened emotional instability and mood disturbances[14]. Such disruptions often manifest as erratic behavior, increased irritability, and a diminished capacity to manage stress, which can severely affect interpersonal relationships and overall quality of life[15]. Additionally, the bidirectional relationship between sleep and mood disorders implies that chronic sleep deprivation not only exacerbates existing mental health conditions but may also serve as a precipitating factor for their development[16]. This highlights the need for integrated therapeutic approaches that incorporate sleep hygiene as a fundamental component of mental health treatment and prevention strategies.

SOLDIERS AND SLEEP DISORDERS

Personnel in the armed forces are subjected to rigorous and continuous training regimens, meticulously designed to ensure they maintain optimal physical fitness and the resilience necessary to endure elevated levels of mental stress inherent in military operations[17]. This comprehensive training is essential for preparing soldiers to meet the diverse and demanding challenges they encounter in both peacetime and combat situations, requiring them to achieve and sustain high levels of physical endurance, strength, agility, and mental acuity[18]. In addition to these physical and mental demands, armed forces personnel are often required to perform night sentry duties on military bases. These night shifts are a critical component of military operations, ensuring the security and readiness of military installations[19]. However, the requirement to work during night hours frequently disrupts normal sleep patterns, resulting in a reduction of total sleep time and misalignment of circadian rhythms[20]. This sleep disruption can lead to cumulative sleep debt, which has been shown to impair cognitive functions such as attention, memory, and decision-making, potentially compromising operational effectiveness and safety[21]. Furthermore, chronic sleep deprivation is associated with an increased risk of various health issues, including metabolic disorders, cardiovascular disease, and mental health conditions such as anxiety and depression, which can further impact the overall well-being and readiness of military personnel[22].

THE RELATIONSHIP BETWEEN SLEEP DEPRIVATION AND CARDIOMETABOLIC ABNORMALITIES

An increasing body of research has elucidated the potential impact of partial sleep deprivation on cardiometabolic abnormalities, highlighting the complex interplay between inadequate sleep and metabolic health[23]. Partial sleep deprivation, characterized by reduced sleep duration over an extended period, has been implicated in the dysregulation of glucose metabolism, leading to insulin resistance and an increased risk of type 2 diabetes[24]. This relationship is mediated by alterations in the autonomic nervous system and increased sympathetic nervous activity, which can exacerbate metabolic dysfunction[25]. Furthermore, insufficient sleep has been shown to disrupt lipid metabolism, contributing to dyslipidemia, which is characterized by elevated levels of triglycerides and low-density lipoprotein cholesterol[26]. These lipid abnormalities are significant risk factors for atherosclerosis and cardiovascular disease[27]. Sleep deprivation also affects the hormonal regulation of appetite, leading to increased levels of ghrelin and decreased levels of leptin, hormones that regulate hunger and energy balance, thereby promoting weight gain and obesity[28]. The cumulative effects of these metabolic disturbances underscore the critical role of sufficient sleep in maintaining cardiometabolic health and preventing the onset of related diseases[29]. As such, public health initiatives emphasizing the importance of sleep hygiene could play a pivotal role in reducing the prevalence of cardiometabolic disorders in populations experiencing high rates of sleep deprivation (Table 1)[30].

Table 1 Findings from recent studies.

Ref.	Population	Methodology	Key findings
Nollet et al[31]	Healthy adults	Polysomnography	Demonstrated increased sympathetic activity and heart rate variability reduction after one night of sleep deprivation
Dettoni et al[32]	Middle-aged individuals	Longitudinal study	Found a significant association between sleep duration and incidence of hypertension over 5 years
Dettoni et al[32]	Obese individuals	Experimental	Showed that 5 nights of restricted sleep led to endothelial dysfunction, as measured by flow-mediated dilation
Dettoni et al[32]	Elderly population	Cross-sectional	Reported higher levels of inflammatory markers in those with sleep disturbances, correlating with increased cardiovascular risk
Orzeł-Gryglewska[33]	Sleep apnea patients	Clinical trial	Indicated improvement in blood pressure and heart rate variability with effective treatment of sleep disorders
Sauvet et al[34]	Young adults	Survey-based	Found that self-reported sleep deprivation correlated with higher rates of perceived stress and cardiovascular symptoms

RESEARCH DESIGN AND PARTICIPANTS

This cross-sectional investigation was part of a larger study examining cardiorespiratory fitness and health among Taiwanese armed forces personnel in 2020[5]. The study population consisted of 867 individuals aged 18 years to 39 years. Inclusion criteria included no current use of medications for hypertension, hyperlipidemia, or diabetes. Participants were required to maintain a regular sleep schedule, with night sentry duties restricted to a maximum of 2 hours to 4 hours, representing only a portion of their overall sleep.

ASSESSMENT OF NIGHT SENTRY DUTY

A questionnaire was used to collect self-reported data on the frequency of night sentry duty over the preceding three months. Participants were categorized into three groups based on their responses: 0, 1-2, or ≥ 3 shifts per month. These duties were limited in duration and did not result in complete sleep deprivation.

CARDIOMETABOLIC PARAMETERS AND DATA COLLECTION

Resting blood pressure and pulse rate (PR) were measured to assess hemodynamic status. The International Diabetes Federation criteria were used to define cardiometabolic risk factors. Fasting plasma glucose, serum triglycerides, and HDL-C levels were determined using an automated analyzer (Olympus AU640, Kobe, Japan).

STATISTICAL ANALYSIS

In the study by Lin et al[5], multivariable linear regression models were used to evaluate the relationships between night sentry duty frequency and PR, blood pressure, and other biomarkers associated with metabolic syndrome (MetS). These models adjusted for age, sex, substance use, body mass index, and cardiorespiratory fitness (model 2). Multivariate logistic regression analysis was conducted to assess the association between night sentry duty (as a categorical variable) and MetS prevalence. Covariates for this analysis were chosen based on their potential influence on MetS. A P value of less than 0.05 was considered statistically significant.

RESULTS OF AN ANALYSIS ON THE INTERACTION BETWEEN DUTY AND CARDIOMETABOLIC HEALTH

The study by Lin et al[5] provides compelling evidence of the cardiometabolic impact of night sentry duties. It was found that increased frequency of night shifts is positively correlated with resting PR and inversely associated with HDL-C levels, which are critical markers of cardiovascular health. Notably, individuals with at least one night shift per month exhibited a heightened risk of impaired fasting glucose, further underscoring the metabolic disruptions linked to sleep deprivation.

The study’s multivariable linear regression analysis confirmed these associations, demonstrating that night sentry duties significantly influence PR, while HDL-C levels decrease as night duty frequency increases. These findings suggest that even partial sleep deprivation, characterized by reduced sleep quality and duration due to night duties, can precipitate notable cardiometabolic changes.

The study presented detailed tables illustrating the associations between night duty frequency and various metabolic markers. For instance, Figure 1A delineates the inverse association between night duty and HDL-C levels, while Figure 1B-D highlights the increased odds of impaired fasting glucose among personnel with frequent night shifts. These tables provide a clear visualization of the data, reinforcing the study's conclusions and emphasizing the need for targeted interventions.

Figure 1 The study presented detailed tables illustrating the associations between night duty frequency and various metabolic markers. A: Regression analysis of metabolic syndrome biomarkers. Data are presented as standardized β and P value using linear regression analysis. Model 1: Age, sex, alcohol drinking, betel nut chewing, cigarette smoking adjustments, model 2: Age, sex, alcohol drinking, betel nut chewing, cigarette smoking, body mass index and time for a run adjustment; B: The Relationship between night sentry duty frequency and metabolic syndrome and its associated characteristics, night duty ≥ 1/month; C: The relationship between night sentry duty frequency and metabolic syndrome and its associated characteristics, night duty 1-2/month; D: The relationship between night sentry duty frequency and metabolic syndrome and its associated characteristics, night duty ≥ 3/month. WC: Waist circumference; HDL-C: High-density lipoprotein cholesterol; TG: Serum triglycerides; FPG: Fasting plasma glucose.

CLINICAL IMPLICATIONS AND FUTURE DIRECTIONS

The findings from this research have significant implications for the health management of military personnel. The increased PR associated with night duties may reflect heightened sympathetic nervous system activity, potentially leading to long-term cardiovascular issues if not addressed. Moreover, the inverse relationship with HDL-C levels could predispose individuals to MetS, a cluster of conditions that increase the risk of heart disease, stroke, and diabetes.

Given these results, there is a pressing need for interventions aimed at mitigating the adverse health effects of night duty. Implementing structured sleep recovery programs and promoting lifestyle modifications, such as regular physical activity and healthy dietary habits, could be effective strategies to enhance the cardiometabolic health of military personnel. Future research should explore the mechanistic pathways underlying these associations to better understand how partial sleep deprivation impacts cardiometabolic health. Longitudinal studies are particularly crucial to establish causal relationships and assess the long-term effects of night duties on health outcomes. Additionally, employing advanced sleep monitoring technologies, such as polysomnography, could provide more accurate assessments of sleep quality and its effects on health.

Furthermore, expanding the demographic scope to include diverse military populations and civilian groups could enhance the generalizability of findings. Research should also consider the role of genetic and environmental factors in mediating the health impacts of sleep deprivation. By integrating biomarker analyses with lifestyle interventions, future studies can develop targeted health strategies that better protect military personnel's health and operational readiness. Such advancements would contribute significantly to our understanding of how nocturnal duties impact cardiometabolic health and inform effective intervention strategies. By addressing these future research directions, we can improve health outcomes and quality of life for military personnel subjected to night duties.

LIMITATIONS OF THE STUDY

In evaluating the findings of Lin et al’s study[5], it is essential to consider several limitations that may impact the generalizability and applicability of the results. First, the study’s cross-sectional design inherently restricts the ability to establish causal relationships between night sentry duties and cardiometabolic alterations. Longitudinal studies are recommended to elucidate the causality and temporal sequence of these associations. Second, the sample was limited to military personnel aged 18-39, which may not represent the broader population. This age and occupational specificity could limit the applicability of the findings to other age groups or non-military individuals. Additionally, the unique stressors and physical demands of military life may influence the generalizability of these findings to civilian populations. Third, the reliance on self-reported data for night sentry duty frequency and lifestyle habits introduces potential biases, such as recall bias or social desirability bias. Although recall within three months should be acceptable, inaccuracies may still occur, affecting the reliability of the findings. Fourth, while the study adjusted for several potential confounders, there may still be unmeasured variables, such as genetic predispositions or other lifestyle factors, that could influence the observed associations. These unmeasured confounders may lead to residual confounding, affecting the study’s conclusions. Fifth, the study did not include detailed assessments of sleep quality or duration using objective measures like polysomnography, which would provide a more accurate depiction of sleep disturbances and their health impacts. Objective assessments are crucial for validating self-reported sleep data and understanding the full extent of sleep-related health risks.

Addressing these limitations in future research could enhance the robustness of the findings and provide more comprehensive insights into the effects of nocturnal duties on health. Specifically, future studies should aim to include more diverse populations beyond military personnel to increase generalizability. Employing a longitudinal design would be beneficial to establish causal relationships. Additionally, incorporating objective measures of sleep, such as polysomnography, and accounting for unmeasured confounders could lead to more accurate and applicable results. Such advancements would contribute significantly to our understanding of how nocturnal duties impact cardiometabolic health and inform effective intervention strategies.

CONCLUSION

The research by Lin et al[5] significantly advances our understanding of the health challenges faced by military personnel due to nocturnal duties. It underscores the critical need for comprehensive strategies that address both the immediate and long-term health impacts of partial sleep deprivation. By integrating biomarker analysis with lifestyle interventions, we can better safeguard the health and operational readiness of armed forces personnel. Future studies should explore the mechanistic pathways underlying these associations and evaluate the efficacy of potential interventions.