Pulmonary Function and Respiratory Health of Military Personnel Before Southwest Asia Deployment

Discussion

During the First Gulf War and the recent Southwest Asian conflicts, there have been unique airborne hazards, including oil well and sulfur mine fires, burn pits, chemical munitions, urban air pollution, and Southwest Asian geologic dusts. Neither the short- nor long-term effects on pulmonary health have been fully elucidated, but the potential detriment to lung function from airborne particulate matter remains. Understanding the underlying respiratory health of deploying military personnel may be critical in identifying potentially susceptible individuals with preexisting respiratory problems and pulmonary dysfunction. Specific interventions could be taken to assure these at risk individuals minimize their exposure to airborne environmental hazards.

This is the first prospective study of deploying military personnel designed to understand and delineate factors potentially associated with development of pulmonary disease in this population. A primary finding is that the current deploying force is older (mean age 32.2 y) and heavier (mean body mass index 27.1 kg/m²) and may have underlying undiagnosed lung disease. Although many individuals reported asthma without a documented formal evaluation, a reported history of asthma was predictive of abnormal spirometry. Wheezing, a clinical surrogate for asthma in many population studies, also increased the odds of abnormal spirometry. Finally, every minute increase in the 2-mile run time increased the odds for abnormal spirometry.

This study is consistent with previous studies demonstrating increased respiratory symptoms in service members deployed to Southwest Asia. The data refute the assumption that all deploying service members are young, fit, and without respiratory symptoms. The study also shows that many deploying service members failed their fitness test or were unable to run 2 miles. Additionally, a sizeable proportion of the deploying force reported a history of asthma regardless of deployment history. Finally, these results correlate conditions such as posttraumatic stress disorder, smoking, and obesity with increased respiratory symptoms. Future studies should take pre-deployment pulmonary function, functional status, and comorbidities into account when analyzing the effect of deployment on the respiratory health of service members.

Deployment-related respiratory symptoms were reported as early as the First Gulf War. Army investigators examining the health effects of the 1991 Kuwaiti oil fires found increased upper-respiratory tract irritation, dyspnea, and cough associated with fire proximity.⁸ However, a cohort study of 1,560 veterans 5 y after that conflict showed no correlation between self-reported asthma and bronchitis and modeled proximity to the oil fires.⁹ Additionally, 10 y post-deployment, there were no PFT differences between a deployed and never-deployed cohort, suggesting no measurable effect from the reported exposures.²⁰ The Millennium Cohort Study, an ongoing Naval Health Research Center survey evaluating the longitudinal health of military personnel, provides additional information. Baseline and follow-up surveys of 46,077 service members (10,753 deployed) found higher rates of newly reported respiratory symptoms in previously deployed compared with never-deployed personnel (14% vs 10%). Similar rates of chronic bronchitis/emphysema (1%) and asthma (1%) were observed in both cohorts.¹¹ Notably, short-term respiratory health effects due to specific exposures have not been identified. United States Army Public Health Command epidemiologic research at enhanced particulate matter surveillance sites found no association with increased particulate matter exposures (primarily geologic dusts) and cardiorespiratory events requiring medical encounters.²¹ The United States Army Public Health Command evaluated trends in rates of chronic lung diseases in the military population from 2001 through 2013. Over the 13-y study period, rates of asthma and chronic bronchitis steadily decreased, whereas an increase in nonspecific bronchitis drove an overall increase in chronic respiratory disease.²²

Ongoing clinical studies are being conducted to characterize chronic respiratory diseases in the redeploying population but are generally limited by a lack of pre-deployment pulmonary data, including PFTs. In 2014, Department of Defense investigators prospectively evaluated 50 military members who reported new-onset dyspnea within 6 months of returning from deployment. Participants completed a standardized evaluation, including full PFTs, methacholine challenge, chest CT imaging, and fiberoptic bronchoscopy. Forty-two percent of subjects had normal findings, whereas another 40% had either asthma or evidence of increased airway hyperreactivity.³ Veterans Affairs investigators completed PFTs on 124 deployed veterans as part of a post-deployment evaluation. Longer deployments were associated with increased bronchodilator responsiveness with a trend toward increased air flow limitation²³

Both asthma and airway hyperreactivity are common in military personnel with respiratory complaints.²¹ These conditions no longer automatically disqualify individuals from military service, and personnel may remain on active duty with well-controlled disease. Extreme Southwest Asian climate conditions, geologic dust, and burn pit smoke exposures may worsen asthma control and increase exacerbations. Roop et al¹⁵ surveyed deploying Army personnel and identified 5% of troops with a pre-deployment diagnosis of asthma. Both asthma subjects and non-asthma subjects had increased respiratory symptoms during deployment; asthma subjects reported poor symptom control in theater. A single-center review of 6,000 Veterans Affairs medical records (ICD-9 diagnostic codes with minimal PFT data) noted higher rates of new-onset asthma in deployed personnel from 2004 to 2007 compared with never-deployed personnel (6.6% vs 4.3%).⁵ The study did not address any asthma symptoms or related conditions that existed pre-deployment. Department of Defense investigators conducted an in-depth medical record review of 400 individuals diagnosed with asthma undergoing a medical fitness-for-duty evaluation. Asthma was confirmed with PFTs in only 78% of the subjects. Fifty percent had never deployed, 25% were diagnosed pre-deployment, and 25% of the asthma subjects were diagnosed post-deployment. There were inadequate data to determine whether this was either undiagnosed preexisting disease aggravated by airborne exposures or new-onset disease in the post-deployment group. However, there were no differences in PFTs or asthma severity based on time of diagnosis or deployment history.²⁴

A workshop at the 2011 Department of Defense/Veterans Affairs Airborne Hazards Conference addressed the adoption of screening spirometry in military personnel. Four issues were raised as potential barriers to implementation: cost, reliability, pre- and post-deployment spirometry, and use of spirometry to detect new pulmonary disease²⁵ The United States Army Public Health Command provided an in-depth analysis for a single spirometry examination and projected start-up costs to be nearly $35 million. Primary issues in periodic spirometry evaluation are to establish good baseline measurement, maintain quality and within-person reproducibility, and identify individuals with excessive lung function decline.²⁶ Currently, the Department of Defense electronic medical record cannot support tracking individual examinations to establish any trend. Furthermore, if the proportion who develop pulmonary disease is limited, as suggested by current epidemiologic data, there would be no benefit in obtaining baseline spirometry for the vast majority of military personnel who never develop pulmonary disease.

Finally, the workshop addressed limiting testing to pre- and post-deployment spirometry. Implementation of pre- and post-deployment spirometry would have significant logistic implications given the numbers (>2.5 million personnel deployed) and the numerous pre-deployment locations. The data in this study suggest possible value in implementing a pre-deployment screening questionnaire for respiratory symptoms and preexisting pulmonary disease. Those with positive responses could then undergo pre-deployment spirometry testing with repeat testing when returning. This approach may better identify personnel with demonstrable post-deployment PFT reductions due to underlying lung disease; however, many personnel may not honestly answer the questions due to a perception that it may prevent deployment or compensation for deployment-related lung disease.

This study had several weaknesses. First, the participants were all soldiers from a single centralized deployment center. Although this is a large single-center sample, the histories, medical conditions, and exposures may not fully represent the entire Army. Other bases and deployment centers may have soldiers with more intense exposures and worse lung function. Additionally, only the Army was represented in this cohort. The conditions endured during deployment of the Marine Corps may be like those of the Army, but the Air Force and Navy have distinct missions that will entail their own unique hazards.

Additionally, all participants had been deemed fit for deployment. It is possible that individuals with severe exposures and subsequent lung disease were unfit for deployment or had separated from the service, thus underestimating the effect of previous deployments on pulmonary function. Many of these questions should be answered with the post-deployment cohort analysis. Additionally, all potential recruits were informed that PFT results would remain confidential, but it is possible that select soldiers with ongoing respiratory problems may have declined participation for fear it might damage their careers. Finally, our study relied nearly completely on self-reporting symptoms and conditions. Most of those reporting a history of asthma did not have an asthma diagnosis in the chart, but as noted above, those with the reported history were more likely to have abnormal PFTs. This strengthens the reliability of the self-reporting in this study.