Many of the studies had other limitations. Few studies measured the stress that troops experienced during deployment; rather, most asked veterans about exposure to possible stressors after their return from deployment. Some studies—such as the congressionally mandated National Vietnam Veterans Readjustment Study (NVVRS), the Vietnam Experience Study (VES), and some Gulf War studies—assessed veterans’ war-zone exposures many years after they had returned home. Furthermore, many studies did not verify veterans’ reported exposures against military records. Finally, although many studies used various scales, such as the Combat Exposure Scale, to determine possible exposures during deployment, the scales did not ascertain the emotional response of the veterans to the exposures; that is, the studies asked only whether exposure to a stressor occurred and not about the degree to which the veterans found the experience to be stressful. Studies that did ascertain veterans’ reactions to stressors, such as seeing a comrade wounded or firing a gun at the enemy, and that asked veterans to rate their responses on a scale, such as “never” to “always,” are rare.
The committee acknowledges that many of the health effects associated with deployment were discussed in a previous volume of the Gulf War and Health series, Volume 4: Health Effects of Serving in the Gulf War. In that volume, the health effects that had been found in deployed Gulf War veterans were identified, and their prevalence compared with the prevalence of the same effects in nondeployed Gulf War veterans. However, that review was restricted to Gulf War veterans; veterans of other conflicts—such as the Vietnam War, World War II, the Korean War, and Operation Enduring Freedom (OEF) and Operation Iraqi Freedom (OIF)—were not considered. Furthermore, that report did not seek to establish whether there was any association between being deployed and specific health effects. As a consequence, although the present committee reviewed many of the same studies as the committee that prepared Volume 4, the assessment process used here is different, as are some of the conclusions because a broader array of studies were considered using defined categories of association.
Each year over a million people receive a diagnosis of cancer in the United States. About one of two American men and one of three American women will have cancer at some point in their lives. Cancer can develop at any age, but about 77% of all cancers are diagnosed in people 55 years old or older. Military personnel during the Gulf War had a mean age of 28 years and therefore are now in their mid-40s. Insufficient time had elapsed for most forms of cancer to be detected among Gulf War veterans by surveys conducted in the 1990s and early 2000s. That is not the case, however, for veterans of the Vietnam War, many of whom are now at an age when most cancers are likely to be diagnosed. Therefore, given the substantial differences in ages between veterans of the Vietnam War and the Gulf War, the studies are discussed separately.
Primary studies for this health effect were those that compared deployed vs nondeployed veteran populations from either the Vietnam War or the Gulf War. A primary study must have indicated that the presence of cancer or death from cancer was confirmed, as by physical examination, medical record review, or death certificates. Of particular concern in studies of Vietnam veterans is possible confounding from exposure to Agent Orange, a toxic herbicide sprayed on foliage in Vietnam.
Most of the studies reviewed in this section did not distinguish between the type of cancers that were seen in or reported by veterans, so the occurrence of cancer is addressed as a specific endpoint. The few studies reporting specific results on testicular cancer, which occurs