New-Onset Asthma and Combat Deployment: Findings From the Millennium Cohort Study

Longitudinal changes in lung function following post-9/11 military deployment in symptomatic veterans

RATIONALE

Exposure to burn pit smoke, desert and combat dust, and diesel exhaust during military deployment to Southwest Asia and Afghanistan (SWA) can cause deployment-related respiratory diseases (DRRDs) and may confer risk for worsening lung function after return.

METHODS

Study subjects were SWA-deployed veterans who underwent occupational lung disease evaluation (n = 219). We assessed differences in lung function by deployment exposures and DRRD diagnoses. We used linear mixed models to assess changes in lung function over time.

RESULTS

Most symptomatic veterans reported high intensity deployment exposure to diesel exhaust and burn pit particulates but had normal post-deployment spirometry. The most common DRRDs were deployment-related distal lung disease involving small airways (DDLD, 41%), deployment-related asthma (DRA, 13%), or both DRA/DDLD (24%). Those with both DDLD/DRA had the lowest estimated mean spirometry measurements five years following first deployment. Among those with DDLD alone, spirometry measurements declined annually, adjusting for age, sex, height, weight, family history of lung disease, and smoking. In this group, the forced expiratory volume in the first second/forced vital capacity (FEV1/FVC) ratio declined 0.2% per year. Those with more intense inhalational exposure had more abnormal lung function. We found significantly lower estimated FVC and total lung capacity five years following deployment among active duty participants (n = 173) compared to those in the reserves (n = 26).

CONCLUSIONS

More intense inhalational exposures were linked with lower post-deployment lung function. Those with distal lung disease (DDLD) experienced significant longitudinal decline in FEV1/FVC ratio, but other DRRD diagnosis groups did not.

Burn Pit Smoke Condensate-Mediated Toxicity in Human Airway Epithelial Cells

Burn pits are a method of open-air waste management that was common during military operations in Iraq, Afghanistan, and other regions in Southwest Asia. Veterans returning from deployment have reported respiratory symptoms, potentially from exposure to burn pit smoke, yet comprehensive assessment of such exposure on pulmonary health is lacking. We have previously shown that exposure to condensates from burn pit smoke emissions causes inflammation and cytotoxicity in mice. In this study, we explored the effects of burn pit smoke condensates on human airway epithelial cells (HAECs) to understand their impact on cellular targets in the human lung. HAECs were cultured at the air-liquid interface (ALI) and exposed to burn pit waste smoke condensates (plywood, cardboard, plastic, mixed, and mixed with diesel) generated under smoldering and flaming conditions. Cytotoxicity was evaluated by measuring transepithelial electrical resistance (TEER) and lactate dehydrogenase (LDH) release; toxicity scores (TSs) were quantified for each exposure. Pro-inflammatory cytokine release and modulation of gene expression were examined for cardboard and plastic condensate exposures. Burn pit smoke condensates generated under flaming conditions affected cell viability, with flaming mixed waste and plywood exhibiting the highest toxicity scores. Cardboard and plastic smoke condensates modulated cytokine secretion, with GM-CSF and IL-1β altered in more than one exposure group. Gene expression of detoxifying enzymes (ALDH1A3, ALDH3A1, CYP1A1, CYP1B1, NQO1, etc.), mucins (MUC5AC, MUC5B), and cytokines was affected by several smoke condensates. Particularly, expression of IL6 was elevated following exposure to all burn pit smoke condensates, and polycyclic aromatic hydrocarbon acenaphthene was positively associated with the IL-6 level in the basolateral media of HAECs. These observations demonstrate that exposure to smoke condensates of materials present in burn pits adversely affects HAECs and that aberrant cytokine secretion and altered gene expression profiles following burn pit material smoke exposure could contribute to the development of airway disease.

Predicting asthma using imbalanced data modeling techniques: Evidence from 2019 Michigan BRFSS data

Studies in the past have examined asthma prevalence and the associated risk factors in the United States using data from national surveys. However, the findings of these studies may not be relevant to specific states because of the different environmental and socioeconomic factors that vary across regions. The 2019 Behavioral Risk Factor Surveillance System (BRFSS) showed that Michigan had higher asthma prevalence rates than the national average. In this regard, we employ various modern machine learning techniques to predict asthma and identify risk factors associated with asthma among Michigan adults using the 2019 BRFSS data. After data cleaning, a sample of 10,337 individuals was selected for analysis, out of which 1,118 individuals (10.8%) reported having asthma during the survey period. Typical machine learning techniques often perform poorly due to imbalanced data issues. To address this challenge, we employed two synthetic data generation techniques, namely the Random Over-Sampling Examples (ROSE) and Synthetic Minority Over-Sampling Technique (SMOTE) and compared their performances. The overall performance of machine learning algorithms was improved using both methods, with ROSE performing better than SMOTE. Among the ROSE-adjusted models, we found that logistic regression, partial least squares, gradient boosting, LASSO, and elastic net had comparable performance, with sensitivity at around 50% and area under the curve (AUC) at around 63%. Due to ease of interpretability, logistic regression is chosen for further exploration of risk factors. Presence of chronic obstructive pulmonary disease, lower income, female sex, financial barrier to see a doctor due to cost, taken flu shot/spray in the past 12 months, 18-24 age group, Black, non-Hispanic group, and presence of diabetes are identified as asthma risk factors. This study demonstrates the potentiality of machine learning coupled with imbalanced data modeling approaches for predicting asthma from a large survey dataset. We conclude that the findings could guide early screening of at-risk asthma patients and designing appropriate interventions to improve care practices.

Military burn pit exposure and airway disease: Implications for our Veteran population

Millions of veterans have been exposed to burn pit smoke during combat deployments throughout the last three decades. Toxic compounds present in burn pit fumes that may cause or exacerbate upper and lower airway diseases include dioxins, polyaromatic hydrocarbons, and particulate matter, among others. There have been several observational studies evaluating the potential role of burn pit exposure in the development of a multitude chronic health conditions, and the veterans Administration has established the Airborne Hazards and Open Burn Pit Registry in 2014. However, specific causality of airway disease from burn pits has been difficult to prove, and there are multiple barriers toward etiologic research. Preclinical models have demonstrated airway dysfunction and inflammation but modeling human exposures remains challenging. Here, we review the current literature on the potential impact of burn pit exposure on chronic airway disease.

Impact of poor air quality while deployed on respiratory health: a systematic review

INTRODUCTION

British military personnel deploy internationally to areas with high levels of ambient air pollution. Air pollution can cause acute respiratory symptoms which lead to concern about potential long-lasting health effects. There is a requirement for evidence-based policy on chronic respiratory disease associated with military deployments to areas with poor air quality (AQ). This literature review examines the published evidence relating to the development of chronic respiratory disease in military personnel after exposure to poor AQ while deployed.

METHODS

A literature search was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines. Embase, MEDLINE and Global health databases were searched for English language studies published since 2014 examining the respiratory health of military personnel deployed to Southwest Asia since 2001. A quality appraisal of selected articles was conducted using the Critical Appraisals Skills Programme checklist and a descriptive review completed.

RESULTS

Eleven studies were found, eight of which had objective outcome measures. Two prospective cohort studies were included; the remainder of the data were retrospective.

CONCLUSION

High rates of respiratory symptoms are reported by personnel who deploy to areas of poor AQ, giving rise to high levels of concern. Spirometry testing has found mild deficits, mostly of an obstructive nature, in a third of those with ongoing symptoms post deployment. These have not been consistently linked with deployment length. An increased risk of asthma appears to be multi-factorial in aetiology and there is no evidence for an increased risk of chronic obstructive pulmonary disease or histological pathology post deployment. At present, there is no definitive evidence of chronic respiratory disease due to exposure to poor AQ while deployed. Further objective longitudinal studies are required to continue to investigate the association, diagnosis and management of those with ongoing symptoms.

Deployment-Related Respiratory Disease: Where Are We?

Military personnel and veterans who have deployed to Afghanistan, Iraq, and parts of Southwest Asia (SWA) since 1990 are at risk of developing a host of respiratory symptoms and deployment-related respiratory diseases (DRRDs). This review aims to summarize our current understanding of DRRD and inform pulmonary practitioners of recent updates to DRRD screening, diagnosis, evaluation, and management. The most common respiratory diseases in these patients include asthma, chronic sinonasal disease, laryngeal disease/dysfunction, and distal lung disease. Pulmonary function testing and chest imaging are the most commonly used diagnostic tools, but techniques such as lung clearance index testing via multiple breath washout, forced oscillation testing/impulse oscillometry, and quantitative chest computed tomography (CT) assessment appear promising as noninvasive modalities to aid in lung disease detection in this population. We also summarize guidance on conducting an occupational and deployment exposure history as well as recommendations for testing. Finally, we discuss the Sergeant First Class Heath Robinson Honoring our Promise to Address Comprehensive Toxics Act of 2022 (PACT Act) that includes a list of health conditions that are "presumptively" considered to be related to SWA military deployment toxic exposures, and provide resources for clinicians who evaluate and treat patients with DRRD.

Contributions of particulate and gas phases of simulated burn pit smoke exposures to impairment of respiratory function

OBJECTIVE

Inhalation of smoke from the burning of waste materials on military bases is associated with increased incidences of cardiopulmonary diseases. This study examined the respiratory and inflammatory effects of acute inhalation exposures in mice to smoke generated by military burn pit-related materials including plywood (PW), cardboard (CB), mixed plastics (PL), and a mixture of these three materials (MX) under smoldering (0.84 MCE) and flaming (0.97 MCE) burn conditions.

METHODS

Mice were exposed nose-only for one hour on two consecutive days to whole or filtered smoke or clean air alone. Smoldering combustion emissions had greater concentrations of PM (∼40 mg/m3) and VOCs (∼5-12 ppmv) than flaming emissions (∼4 mg/m3 and ∼1-2 ppmv, respectively); filtered emissions had equivalent levels of VOCs with negligible PM. Breathing parameters were assessed during exposure by head-out plethysmography.

RESULTS

All four smoldering burn pit emission types reduced breathing frequency (F) and minute volumes (MV) compared with baseline exposures to clean air, and HEPA filtration significantly reduced the effects of all smoldering materials except CB. Flaming emissions had significantly less suppression of F and MV compared with smoldering conditions. No acute effects on lung inflammatory cells, cytokines, lung injury markers, or hematology parameters were noted in smoke-exposed mice compared with air controls, likely due to reduced respiration and upper respiratory scrubbing to reduce the total deposited PM dose in this short-term exposure.

CONCLUSION

Our data suggest that material and combustion type influences respiratory responses to burn pit combustion emissions. Furthermore, PM filtration provides significant protective effects only for certain material types.

Potential for repurposing oral hypertension/diabetes drugs to decrease asthma risk in obesity

OBJECTIVE

Risk for asthma in the overweight/obese may be mediated by adiponectin and peroxisome proliferator activated receptor pathways and may be reduced by the use of oral drugs impacting these pathways, such as angiotensin converting enzyme inhibitors (ACE-I), thiazolidinediones (TZD), and angiotensin receptor blockers (ARB). Our study objective was to determine whether ACE-I, TZD, and/or ARB use in overweight/obese adults with diabetes mellitus and/or hypertension is associated with a lower risk for incident asthma.

METHODS

Using an existing cohort of American veterans, we performed a longitudinal data analysis over 15 years. Exposure was defined by the prescription pickup of ACE-I, TZD, and/or ARB for at least 4 weeks. The outcome, time until new-onset of clinician-diagnosed asthma, was studied using survival analysis. The propensity scoring method controlled for treatment selection bias.

RESULTS

2.83 million eligible veterans, including 77,278 with incident asthma, were studied. As compared to those unexposed, the use of ACE-I alone, TZD alone, or their combinations were each associated with decreased risk for incident asthma (hazard ratios of 0.88, 0.74, and 0.20, respectively; p < 0.001 for all analyses in the fully adjusted statistical models). TZD lowered the risk among racial/ethnic minority subjects more than among White participants (p < 0.001). On the other hand, ARB use alone or in combination with TZD was associated with a higher risk for incident asthma.

CONCLUSIONS

Use of ACE-I and/or TZD was associated with a lower risk for incident asthma in overweight/obese patients with diabetes mellitus and/or hypertension.

Military deployment-related respiratory problems: an update

PURPOSE OF REVIEW

Military personnel deployed to Southwest Asia and Afghanistan were potentially exposed to high levels of fine particulate matter and other pollutants from multiple sources, including dust storms, burn pit emissions from open-air waste burning, local ambient air pollution, and a range of military service-related activities that can generate airborne exposures. These exposures, individually or in combination, can have adverse respiratory health effects. We review exposures and potential health impacts, providing a framework for evaluation.

RECENT FINDINGS

Particulate matter exposures during deployment exceeded U.S. National Ambient Air Quality Standards. Epidemiologic studies and case series suggest that in postdeployment Veterans with respiratory symptoms, asthma is the most commonly diagnosed illness. Small airway abnormalities, most notably particularly constrictive bronchiolitis, have been reported in a small number of deployers, but many are left without an established diagnosis for their respiratory symptoms. The Promise to Address Comprehensive Toxics Act was enacted to provide care for conditions presumed to be related to deployment exposures. Rigorous study of long-term postdeployment health has been limited.

SUMMARY

Veterans postdeployment to Southwest Asia and Afghanistan with respiratory symptoms should undergo an exposure assessment and comprehensive medical evaluation. If required, more advanced diagnostic considerations should be utilized in a setting that can provide multidisciplinary expertise and long-term follow-up.

Short-term PM exposure and social stress cause pulmonary and cardiac dysfunction

Ambient particulate matter (PM) exposure increases risk for cardiopulmonary health problems which may be exacerbated in a stressful environment. Co-exposure to PM and stress characterizes the experience of many deployed military personnel and first responders but has not been thoroughly investigated. This is especially relevant to military personnel who have been exposed to high PM levels in conjunction with stressful military conflict situations. To understand the mechanisms and time-course of the health consequences following burn pit exposure, we exposed mice to moderate levels of ambient PM less than 2.5 μM in diameter (PM_2.5) alone or in combination with psychological stress. We found male mice exposed to PM_2.5 alone or in combination with stress had significantly reduced pulmonary function when subjected to methacholine, indicating increased airway hyperreactivity. These mice experienced increased goblet cell hyperplasia in their lungs, with no change in alveolar density. Mice exposed to PM_2.5 and/or stress also exhibited reduced cardiac contractility, right ventricular (RV) output, and changes in RV capillary density and cardiac inflammatory markers. Taken together, these data indicate that short-term exposure to PM_2.5 with or without stress causes a clear reduction in pulmonary and cardiac function. We believe that this model is well-suited for the study of military and other occupational exposures, and future work will identify potential mechanisms, including the inflammatory progression of these co-exposures.

Characterization of Immunopathology and Small Airway Remodeling in Constrictive Bronchiolitis

Rationale: Constrictive bronchiolitis (ConB) is a relatively rare and understudied form of lung disease whose underlying immunopathology remains incompletely defined. Objectives: Our objectives were to quantify specific pathological features that differentiate ConB from other diseases that affect the small airways and to investigate the underlying immune and inflammatory phenotype present in ConB. Methods: We performed a comparative histomorphometric analysis of small airways in lung biopsy samples collected from 50 soldiers with postdeployment ConB, 8 patients with sporadic ConB, 55 patients with chronic obstructive pulmonary disease, and 25 nondiseased control subjects. We measured immune and inflammatory gene expression in lung tissue using the NanoString nCounter Immunology Panel from six control subjects, six soldiers with ConB, and six patients with sporadic ConB. Measurements and Main Results: Compared with control subjects, we found shared pathological changes in small airways from soldiers with postdeployment ConB and patients with sporadic ConB, including increased thickness of the smooth muscle layer, increased collagen deposition in the subepithelium, and lymphocyte infiltration. Using principal-component analysis, we showed that ConB pathology was clearly separable both from control lungs and from small airway disease associated with chronic obstructive pulmonary disease. NanoString gene expression analysis from lung tissue revealed T-cell activation in both groups of patients with ConB with upregulation of proinflammatory pathways, including cytokine-cytokine receptor interactions, NF-κB (nuclear factor-κB) signaling, TLR (Toll-like receptor) signaling, T-cell receptor signaling, and antigen processing and presentation. Conclusions: These findings indicate shared immunopathology among different forms of ConB and suggest that an ongoing T-helper cell type 1-type adaptive immune response underlies airway wall remodeling in ConB.

Longitudinal Changes in Spirometry in Deployed Air Force Firefighters

INTRODUCTION

Inhalational exposures are common among service members who deploy to southwest Asia. The objective of this study is to determine if deployed Air Force firefighters have any decline in spirometry related to deployment.

METHODS

This study is a retrospective chart review.

RESULTS

The database search identified 302 firefighters with documentation of two separate spirometry examinations. For deployed firefighters, mean change in forced expiratory volume at 1 second (FEV1) percent predicted was -1.01 ± 7.86, forced vital capacity (FVC) was -0.46 ± 10.26 predicted, and mid-expiratory flow (FEF25-75) was -0.13 ± 12.97. For firefighters who had never deployed, mean change in FEV1 percent predicted was +0.08 ± 7.09, FVC was +0.72 ± 7.75, and FEF25-75 was -0.66 ± 16.17.

CONCLUSION

There does not appear to be evidence that deployment causes a significant change in lung function as measured by spirometry.

The Millennium Cohort Study: The First 20 Years of Research Dedicated to Understanding the Long-Term Health of US Service Members and Veterans

The Millennium Cohort Study, the US Department of Defense's largest and longest running study, was conceived in 1999 to investigate the effects of military service on service member health and well-being by prospectively following active duty, Reserve, and National Guard personnel from all branches during and following military service. In commemoration of the Study's 20th anniversary, this paper provides a summary of its methods, key findings, and future directions. Recruitment and enrollment of the first 5 panels occurred between 2001 and 2021. After completing a baseline survey, participants are requested to complete follow-up surveys every 3 to 5 years. Study research projects are categorized into 3 core portfolio areas (psychological health, physical health, and health-related behaviors) and several cross-cutting areas and have culminated in more than 120 publications to date. For example, some key Study findings include that specific military service-related factors (e.g., experiencing combat, serving in certain occupational subgroups) were associated with adverse health-related outcomes and that unhealthy behaviors and mental health issues may increase following the transition from military service to veteran status. The Study will continue to foster stakeholder relationships such that research findings inform and guide policy initiatives and health promotion efforts.

Respiratory symptoms, lung function, and fraction of exhaled nitric oxide before and after assignment in a desert environment-a cohort study

BACKGROUND

Inhalation of small particulate matter (PM 2.5) may be associated with development of respiratory disease. Increased respiratory symptoms have been reported among military staff after service in countries with recurrent desert storms.

OBJECTIVE

The aim was to investigate whether an assignment in a desert environment and exposure to desert storms are associated with negative effects on respiratory health.

METHODS

In two cohorts of Swedish soldiers serving in Mali as part of the United Nations stabilization forces, examination with spirometry, determination of fraction of exhaled nitric oxide (FeNO), and a questionnaire including participant characteristics, symptoms, and exposure was performed before and after service. Ambient air sampling was conducted on-site. Paired t-test was used to compare pre- and post-variables on lung function data, FeNO and symptom level.

RESULTS

Most indoor and outdoor air measurements of dust and silica were within the Swedish occupational exposure limit for PM2.5 and silica (<0.10-2.7 mg/m³ and <0.002-0.40 mg/m³, respectively) as well as for respirable dust and silica (0.056-0.078 mg/m³and 0.0033-0.025 mg/m³, respectively). In the subgroup of participants with reported exposure to desert storms during the stay in Mali, forced expiratory volume in 1 s (FEV₁) was significantly lower after exposure than before the mission (mean litres (SD) 4.21 ± 0.66 vs 4.33 ± 0.72, p = 0.021).

CONCLUSION

Exposure to a desert storm was associated with a decrease in FEV₁. Exposure to small particulate matter may contribute to the development of respiratory disease and thus spirometry should be performed after occupational exposure to desert storms.

The Impact of Deployment and Combat Exposure on Physical Health Among Military Personnel: A Systematic Review of Incidence, Prevalence, and Risks

OBJECTIVES

The impact of deployment and combat on mental health of military personnel is well described. Less evidence is available to demonstrate and summarize the incidence, prevalence, and risks of these exposures on physical health. This study aims to (1) systematically review the available literature to determine the incidence and prevalence of physical health conditions among military personnel during and after deployment and (2) investigate the risks of deployment and combat exposure on physical health.

METHODS

A systematic review using the PubMed and EMBASE databases was performed. The literature search was limited to articles written in English, published from 2000 through 2019. The quality of studies was assessed with the Joanna Briggs Institute Appraisal Checklist. The results were grouped per system or condition of physical health and presented by forest plots without a combined effect size estimate.

RESULTS

Thirty-two studies were found eligible for this review. We identified a wide variety of incidence and prevalence rates of numerous physical health conditions and a high heterogeneity across the included studies. Acute respiratory symptoms, diarrhea, musculoskeletal injuries, pain, and tinnitus were found to be the most incident or prevalent conditions. Except for hearing loss, no associations with deployment and physical health problems were observed. An increased risk for asthma, headache, hearing loss, and pain was reported in relation to the combat exposure.

CONCLUSION

Given the characteristics of included studies and extracted data, the magnitude of the found differences in incidence and prevalence rates is most likely to be due to methodological heterogeneity. The specific exposures (e.g., infrastructure, environmental conditions, and activities during deployment) are suggested to be the determinants of (post) deployment physical health problems and need to be addressed to decrease the impact of deployment. Findings from this systematic review highlight which conditions should be addressed in response to service members' health and wellness needs in the (post)deployment phase and may be used by clinicians, researchers, and policy-makers. However, knowledge gaps regarding the potential risk factors during deployment and combat still exist. Studies using consistent methods to define and measure the physical health conditions and specific exposures are needed.

Exercise-Induced Bronchoconstriction in Iraq and Afghanistan Veterans With Deployment-Related Exposures

INTRODUCTION

Acute exposure to high-levels of ambient fine particulate matter while exercising results in airway narrowing, but the long-term effects of repeated exposure on exercise-induced bronchoconstriction (EIB) are not well known. The goal of this preliminary study is to determine the rate of EIB among a sample of non-treatment seeking veterans deployed to Iraq and Afghanistan.

MATERIALS AND METHODS

Twenty-four veterans (median [interquartile range]: 35.0 [27.3, 45] years) without history of asthma volunteered for this study. Spirometry was assessed before and after a standardized exercise challenge. A positive EIB response was defined as an exercise-induced fall in forced expiatory volume in 1 second ≥10%. Secondary criteria (peak flow ≥10% or mid-expiratory flow ≥15%) were also considered as an estimate of probable EIB.

RESULTS

A positive EIB response was observed in 16.7% and probable EIB response was observed in 41.7% of our sample. Median deployment length to Iraq or Afghanistan was 13.0 [10.3, 17.5] months and the median time since deployment was 4.2 [2.7, 7.7] years. At the time of testing, veterans reported persistent cough (58.3%), wheeze (37.5%), and shortness of breath (37.5%). During deployment, veterans reported exposure to dust and sand (70.8%), smoke from burn pits (66.7%), vehicle exhaust (83.3%), and regional air pollution (26.0%) on most days or daily.

CONCLUSIONS

Approximately 17% of our sample of non-treatment seeking deployed Iraq and Afghanistan veterans demonstrated EIB, similar to the general population prevalence. However, persistent respiratory symptoms and alternative indices of probable EIB supports continued monitoring of this population.

Respiratory Health after Military Service in Southwest Asia and Afghanistan. An Official American Thoracic Society Workshop Report

Since 2001, more than 2.7 million U.S. military personnel have been deployed in support of operations in Southwest Asia and Afghanistan. Land-based personnel experienced elevated exposures to particulate matter and other inhalational exposures from multiple sources, including desert dust, burn pit combustion, and other industrial, mobile, or military sources. A workshop conducted at the 2018 American Thoracic Society International Conference had the goals of: 1) identifying key studies assessing postdeployment respiratory health, 2) describing emerging research, and 3) highlighting knowledge gaps. The workshop reviewed epidemiologic studies that demonstrated more frequent encounters for respiratory symptoms postdeployment compared with nondeployers and for airway disease, predominantly asthma, as well as case series describing postdeployment dyspnea, asthma, and a range of other respiratory tract findings. On the basis of particulate matter effects in other populations, it also is possible that deployers experienced reductions in pulmonary function as a result of such exposure. The workshop also gave particular attention to constrictive bronchiolitis, which has been reported in lung biopsies of selected deployers. Workshop participants had heterogeneous views regarding the definition and frequency of constrictive bronchiolitis and other small airway pathologic findings in deployed populations. The workshop concluded that the relationship of airway disease, including constrictive bronchiolitis, to exposures experienced during deployment remains to be better defined. Future clinical and epidemiologic research efforts should address better characterization of deployment exposures; carry out longitudinal assessment of potentially related adverse health conditions, including lung function and other physiologic changes; and use rigorous histologic, exposure, and clinical characterization of patients with respiratory tract abnormalities.

Clinical Evaluation of Deployed Military Personnel With Chronic Respiratory Symptoms: Study of Active Duty Military for Pulmonary Disease Related to Environmental Deployment Exposures (STAMPEDE) III

BACKGROUND

Chronic respiratory symptoms are frequently reported after Southwest Asia deployment in support of combat operations. The full spectrum of clinical lung diseases related to these deployments is not well characterized.

METHODS

Military personnel with chronic symptoms, primarily exertional dyspnea, underwent a standardized cardiopulmonary evaluation at two tertiary medical centers. Pulmonary function testing consisted of spirometry, lung volume, diffusing capacity, impulse oscillometry, and bronchodilator testing. Further testing included methacholine challenge, exercise laryngoscopy, high-resolution CT scan, ECG, and transthoracic echocardiography.

RESULTS

A total of 380 participants with a mean age of 38.5 ± 8.4 years completed testing. Asthma was the most common diagnosis in 87 patients (22.9%) based on obstructive spirometry/impulse oscillometry and evidence of airway hyperreactivity, whereas another 57 patients (15.0%) had reactivity with normal spirometry. Airway disorders included 25 (6.6%) with laryngeal disorders and 16 (4.2%) with excessive dynamic airway collapse. Interstitial lung disease was identified in six patients (1.6%), whereas 11 patients (2.9%) had fixed obstructive lung disorders. Forty patients (10.5%) had isolated pulmonary function abnormalities and 16 (4.2%) had miscellaneous disorders. The remaining 122 patients (32.1%) with normal studies were classified as undiagnosed exertional dyspnea. Significant comorbidities identified included elevated BMI > 30 kg/m² (34.2%), smoking (36.4%), positive allergy testing (43.7%), sleep apnea (38.5%), and esophageal reflux (13.6%). Mental health disorders and posttraumatic stress disorder were likewise common.

CONCLUSIONS

Postdeployment pulmonary evaluation should focus on common diseases, such as asthma and airway hyperreactivity, and include testing for upper airway disorders. Diffuse lung diseases were rarely diagnosed, whereas numerous comorbidities were common.

Environmental Exposures and Asthma in Active Duty Service Members

PURPOSE OF REVIEW

Reports of respiratory symptoms, including asthma and hyper-reactive airway disease, have been more numerous in the media and medical literature since active duty service members (SM) began to support campaigns in South West Asia (SWA). Numerous environmental exposures have been reported and this review assesses the available evidence surrounding exposures, confounding conditions, and attempts to develop screening mechanisms.

RECENT FINDINGS

While particulate matter exposures and particularly exposure to burn pits have garnered much attention, a 2010 Armed Forces Health Surveillance Center report and 2011 Institute of Medicine publication did not identify a link between exposure to particulate matter with SM respiratory disease. The "Study of Active Duty Military for Pulmonary Disease related to Environmental Deployment Exposure," (STAMPEDE) and STAMPEDE II have not identified effective forms of routine screening and these and other sources point to the importance of other factors in SM respiratory disease. These include higher than anticipated rates of tobacco use in deployed settings, impacts of obesity, recurrence of childhood asthma, and of confounding conditions such as Paradoxical Vocal Fold Motion. As with the general population, a complex set of clinical inputs and environmental exposures surround asthma and similar respiratory processes in SM. Concrete relationships and mechanisms for assessment continue to be assessed and refined, but clear associations and pathways have remained elusive.