Although an association between deployment and respiratory effects was noted in some studies that assessed respiratory effects on the basis of self-reports of symptoms, studies that used more objective markers of respiratory disease (such as pulmonary-function tests and respiratory examinations) did not document a consistent relationship between deployment and respiratory disease.

None of the primary studies considered for respiratory effects (one study in Vietnam veterans and six in Gulf War veterans) found a higher risk of chronic respiratory effects in deployed than in nondeployed veterans on the basis of objective measures of pulmonary function and disease. However, deployed veterans reported more symptoms of respiratory effects, such as cough and shortness of breath, in one Gulf War study and of asthma and chronic bronchitis in a second Gulf War study than did the nondeployed veterans. In both studies, on examination, pulmonary function was not compromised in the deployed groups. Of the 12 secondary studies that relied on self-reports of respiratory effects, 11 found that deployed Gulf War veterans reported more symptoms of respiratory effects. The one secondary study that assessed hospitalizations of Gulf War veterans for respiratory disease found no increase in risk.

Results regarding the relationship between PTSD and respiratory effects are mixed. No primary studies were identified; in the secondary studies, although modest increases in respiratory symptoms were reported in Vietnam veterans and in female veterans with PTSD, no such increase was seen in a small study of Gulf War veterans.

Respiratory conditions are common in veterans regardless of deployment status. The population burden of asthma and COPD in all U.S. adults is high, but COPD takes many years to develop and is uncommon in people under the age of 50 years. The prevalence of respiratory disease is even higher in adults with a history of cigarette-smoking. Thus, with additional followup of the veterans, future studies might show an effect of war-related stress. Many studies fail to make clear whether there is a direct relationship between deployment stress and increased pulmonary complaints as opposed to some other mediating or moderating factor. Veterans of the Gulf War were exposed to numerous air pollutants, including smoke from oil-well fires, pesticides, exhaust from tent heaters, and possibly chemical-warfare agents. Veterans of other conflicts may have similar exposures to toxicants and to other agents, such as Agent Orange in the case of Vietnam veterans. Many of the studies considered by the committee identified other possible exposures of veterans, particular those who were deployed to the Gulf War, but were unable to eliminate possible confounding when assessing risks. The association between increased Gulf War deployment and cigarette-smoking is unknown. Cigarette-smoking was not controlled in the analyses in a number of the studies so it is unclear to what degree smoking may account for any increase in respiratory symptoms, complaints, or disease.

The few studies that collected more-objective data on respiratory outcomes—such as data on pulmonary-function testing, data from physical examinations, and data on verified pulmonary events from medical-record review or physician questionnaires—did not find strong indications of increased risk among veterans with combat deployment. The vast majority of available studies of veterans with respiratory diseases were not specifically designed to focus on these outcomes as primary variables but derived information from a larger nonspecific self-administered symptom checklist.

The committee concludes that there is inadequate/insufficient evidence to determine whether an association exists between deployment to a war zone and chronic respiratory effects.

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