The Gulf War was short in duration but the consequences linger 8 years after the fighting ceased. Some veterans of that conflict report debilitating health problems that they believe are connected to service in the Gulf.* Once healthy and fit soldiers report they are no longer able to engage in normal daily activities, much less the rigorous tasks they completed in the military. Symptoms commonly described include fatigue, memory loss, severe headaches, muscle and joint pain, and rashes (Fukuda et al., 1998; Iowa Persian Gulf Study Group, 1997). These veterans want to know why they are ill, what can be done to make them better, and whether the government is doing all it can to help them. They have taken their case to the media, to Congress, to the Department of Veterans Affairs (VA), and to the Department of Defense (DoD).

With concern about the veterans' reports escalating, numerous activities were launched to investigate veterans' health concerns. Various aspects of the problem have been studied by a Presidential Advisory Committee (PAC), the General Accounting Office (GAO), a special investigation unit of the Committee on Veterans Affairs of the U.S. Senate, the Centers for Disease Control and Prevention (CDC), the Institute of Medicine (IOM), and independent researchers. The federal government has spent more than $230 million to fund research efforts and diagnostic programs to answer the many questions raised.

Research studies have compared Gulf War veterans to other contemporary military veterans to determine whether they have higher hospitalization rates

(Gray et al., 1996; Knoke and Gray, 1998), a greater incidence of reproductive problems (Araneta et al., 1997; Cowan et al., 1997), or higher mortality rates (Kang et al., 1996). One study has compared the health of Iowa Gulf War veterans to that of Iowa veterans who were not deployed to the war (Iowa Persian Gulf Study Group, 1997). Reviews of scientific literature and new research have been conducted to try to determine whether any veterans' Gulf War exposures could be responsible for their symptoms, and various approaches to treatment of veterans' problems have been tried.

The findings of these studies, evidence from the many efforts to evaluate Gulf War veterans' health conducted by the aforementioned bodies, and additional independent research support several conclusions:

• No single diagnosable illness or set of symptoms with a known etiology characterizes either Gulf War veterans in general or a subset of veterans who are experiencing some kind of health problem.
• VA and DoD data systems do not demonstrate a higher incidence of hospitalizations or deaths among Gulf War veterans than among other veterans. The incidence of birth defects in children and the incidence of health problems among spouses are not higher for the Gulf War cohort than for other veteran cohorts.
• There does seem to be a higher prevalence of some symptoms among veterans who served in the Gulf War as compared to nondeployed veterans. The primary symptoms include fatigue, difficulty concentrating, memory loss, skin rash, headache, and muscle and joint pain.
• Many Gulf War veterans receive no diagnosis that explains their symptoms. Many of these complaints produce no observably physiological indicators, and must be measured by self-reports of those experiencing them. For some veterans, the symptoms are severe enough to be disabling; others experience milder symptoms that still allow some level of normal daily activity, while others report no problems at all.
• Several possible explanations for the symptoms experienced by Gulf War veterans have been suggested. They include exposure to vaccines, toxic chemicals, chemical and biological warfare agents, and depleted uranium, as well as stress associated with either exposure to battlefield stimuli or rapid deployment with associated uncertainty about time and circumstances of return home. Veterans' symptoms have not been found to be correlated with exposure to any particular physical or psychological stimulus. Although future epidemiological studies may show such an association, the extant literature is limited and results are inconclusive.
• No strong evidence exists for any effective treatment of these symptoms as a single disease entity. There is little published evidence of successful treatment of symptom clusters.

Many areas of uncertainty remain. For example, no one has yet determined the extent of the problem, that is, the number of veterans who have symptoms or

illnesses that they attribute to service in the Gulf War. Also, no one yet knows whether the health status of the Gulf War veteran population is better than, worse than, or the same as that of veterans who were not deployed to the Gulf War, although some studies have found higher levels of reported symptoms among Gulf War veterans. There has been no systematic evaluation of whether the health status of these veterans is changing and, if so, how.

In December 1997, the VA and the DoD asked the IOM to convene a group of experts to consider the numerous questions regarding the health of Gulf War veterans and then to determine how best to address the issues of measuring and monitoring the health of these veterans. The charge to the IOM was to: "(1) identify relevant questions regarding the evaluation of the health status of active-duty troops and veterans deployed to the Gulf War; (2) identify issues to be addressed in the development of study designs and methods that would be used to answer such questions; and (3) develop a research design(s) and methods that could be used to address such questions."

The IOM convened the Committee on Measuring the Health of Gulf War Veterans, which is composed of experts in outcomes analysis, study design, research methods, statistics, epidemiology, health status measurement, military health databases, clinical medicine, and Gulf War veterans' health. Between May 1998 and April 1999, the committee met five times. In addition, a workshop was held in May 1998 to obtain background information on the health concerns of Gulf War veterans and an overview of relevant research. During subsequent meetings the Committee reviewed and analyzed additional information on: symptoms, complaints, and diagnoses of veterans; completed population-based and sample-survey research on the health of Gulf War veterans from the United States, Canada, and the United Kingdom; VA and DoD health databases; the reports of the PAC, the GAO, and other IOM committees; and books and articles describing and evaluating approaches to and instruments for measuring health status.

The first component of the study charge directed the committee to identify questions important in evaluating the health and well being of active-duty troops and veterans who were deployed to the Gulf War. Through a review of statements and presentations by major interested groups, the committee identified questions that appear critical to those groups (see Table 1). Some of these questions can be addressed by research, others are in the realm of policy.

Furthermore, many individuals and groups are now beginning to ask if these questions apply only to the health of Gulf War veterans or if they also apply to the health of veterans of any conflict.

The committee concluded that a single study cannot satisfy all information needs concerning the health of Gulf War veterans. Because these questions are diverse and require the application of various types of research and health measurement to address them thoroughly, the committee has developed and recommends a "portfolio" of research activities that includes population studies, health services research, and clinical and biomedical investigations.

Of fundamental importance is the need to know how many Gulf War veterans are suffering from health problems that affect their ability to function; whether the prevalence of such problems among Gulf War veterans is consistent with their prevalence among the general public or among other veterans groups; and whether the health of veterans is getting better, staying the same, or deteriorating with time.

Because these fundamental questions address both the health of Gulf War veterans at specific time points and changes over time, the committee recommends that a prospective cohort study of the population of Gulf War veterans be conducted. Such a study should include appropriate comparison groups.

Additionally, the committee recommends that the prospective cohort study investigate the following four questions:

1.	How healthy are Gulf War veterans?
2.	In what ways does the health of Gulf War veterans change over time?
3.	Now and in the future, how does the health of Gulf War veterans compare with that of

• the general population;
• persons in the military at the time of the Gulf War but not deployed;
• persons in the military at the time of the Gulf War who were deployed to nonconflict areas; and
• persons in the military deployed to other conflicts, such as Bosnia, Somalia?

Key comparison groups must be included in the study design to provide a basis for drawing conclusions about reasons for levels and trends in the health status of Gulf War veterans. Comparisons with the general population provide a basis for ascertaining whether the health experience of Gulf War veterans simply reflects levels and trends in the general population, or is different because of some aspect of military service. Additionally, a general population comparison

group will provide a basis for distinguishing changes in health of Gulf War veterans that are attributable to factors such as economic conditions experienced by veterans since the War versus participation in the War. For example, decline in health may be attributable to economic recession, as was found for the general population in an analysis of the Health and Activity Limitation Index over the 1984–1994 interval (Erickson, in press). Comparisons with those in the military at the time of the Gulf War but not deployed provide a basis for ascertaining whether selection for deployment is associated with differences in health levels and trends.

Comparisons with a sample of individuals who were in the military and who were deployed to theater but were deployed to a "safe" area provide a basis for ascertaining whether selection for war-theater deployment had health consequences or whether health levels and trends resulted simply from selection for deployment to the Gulf region. Finally, comparisons with a sample of veterans of other conflicts (e.g., Bosnia and Somalia) provide a basis for ascertaining whether health levels and trends of Gulf War veterans are a consequence of serving in any conflict or the result of unique aspects of the Gulf War situation.

The committee recognizes that many completed studies have made important contributions to our understanding of the issues and problems affecting the health of Gulf War veterans and that other valuable studies are currently underway or will be undertaken in the coming years. Various agenda-setting bodies are directing the flow of resources to these investigations. The committee believes, however, that the contributions of future individual studies will be enhanced if a mechanism exists for linking these studies through the collection of a core set of key data elements, thereby allowing comparisons across all research undertaken. Linking studies in this manner is an essential feature of the committee's research portfolio concept.

The committee believes that this portfolio approach, which encompasses various study designs and related methods, will, if implemented, lead to a greater understanding of the longer-term health effects of service in the Gulf War. Therefore, the committee recommends that multiple studies be initiated through a research portfolio with three components: population studies, health services research studies, and biomedical and clinical investigations.

The committee recommends that a core set of data on health be collected in all studies and include measures of:

• death and duration of life,
• impairment,
• functional status,
• health perceptions, and
• opportunity [the capacity for health, the ability to withstand stress, and physiological reserve].

The committee recommends that a core set of data on the correlates of health be collected in all studies. These data should include measures of individual and environmental characteristics that are associated with differences in health. Individual characteristics of interest include:

• biology and life course,
• lifestyle and health behavior,
• illness behavior,
• personality and motivation, and
• values and preferences.

Environmental characteristics of interest include:

• social and cultural,
• economic and political,
• physical and geographic, and
• health and social care.

The committee further recommends that the prospective cohort study of Gulf War veterans (and appropriate comparison groups) serve as the foundation for the entire portfolio of activities.

The committee has not attempted to develop detailed design specifications for such a study, but it has identified key methodological considerations. Specifically, the committee recommends the prospective cohort study incorporate the following features:

• multiple cohorts, one for each group of interest;
• multistage sampling with initial cluster sampling followed by stratified random sampling within clusters; and
• random and representative selection of participants within clusters; hypothesis-driven oversampling of specific population subgroups; and multiple modes of interviewing, including telephone and in-person interviewing.

Although the committee is persuaded that a prospective cohort study is a necessary and appropriate method for monitoring the health of Gulf War veterans, it recognizes that such a study requires a major commitment of resources. Therefore, the committee recommends a pilot study be conducted to determine the feasibility and cost of the prospective cohort study. The pilot study should include an assessment of the following points:

• for each of the five cohorts, identification of the universe from which the sample is to be drawn, especially the Gulf War veteran sample;
• willingness of members of each cohort to participate in the baseline study;

• modes of data collection; and
• use of incentives to maximize response rates.

An independent advisory board should be established to ensure high-quality research throughout the program and to set policies for and monitor the progress of the long-term survey and research portfolio of studies of the health of Gulf War veterans. This advisory board should be independent in order to ensure its scientific integrity and the public perception of validity of research results.

The committee sees several benefits of such an advisory board. First, it would provide a means for engaging a broad range of expertise in the oversight of this major, and complicated, effort to monitor and improve the health of veterans of military conflict. Second, its agenda can be quite broad and encompass more than might be accomplished by any single federal department. Third, it would provide a visible mechanism for public accountability. Finally, such an advisory board can command national attention when it speaks or acts; it is thus in a position to call for direct, immediate, and meaningful action on the conclusions and implications of critical findings.

Specific functions of the advisory board should include a review of the scientific and methodological merit of proposed and ongoing studies in the research portfolio. This review would take into account not only the research activities being supported or carried out within the structure proposed in this report, but also changes in various other programs within the federal government and the private sector.

Specifically, the committee recommends that an independent advisory board oversee the conduct of the prospective cohort study. The advisory board should

• be an independent, scientific, and policy-oriented body composed of experts in clinical medicine, epidemiology, health status and health outcomes assessment; veterans' health issues; health services research; social, behavioral, physical, and biomedical sciences; survey research; statistics; national health databases; health policy; and members of the public who represent Gulf War veterans.
• review, in a timely fashion, requests for proposals developed by the funding agencies to conduct the prospective cohort study recommended by the committee.
• evaluate the methodological design of the cohort study.
• set the minimum requirements for policies on:
• • methods for locating and retaining study participants,
  • informed consent,
  • respondent burden,
  • confidentiality and security of data,
  • use of incentives, and

• responsibility for reporting identified individual or public health threats.
• • evaluate the success of the prospective cohort study at the end of the 10-year study period.
  • submit a report to Congress every 2 years.

As this report is being prepared, 8 years have elapsed since the last U.S. troops returned from the Gulf War. During that time enormous effort has been expanded in attempts to solve the puzzle of the effects of the Gulf War on the health of those deployed to fight in that war. Veterans have lobbied extensively to ensure that their concerns are heard and problems are addressed. Numerous investigations by Congress, the GAO, the PAC, and the IOM have attempted to tease out factors contributing to those problems. VA and DoD have established examination programs focused on diagnosing and treating Gulf War veterans' complaints. The Department of Health and Human Services (HHS), VA, and DoD have funded more than 120 research projects aimed at various aspects of the problem. Independent researchers have engaged in additional research focused on the health of Gulf War veterans.

VA has undertaken the enormous task of coordinating research efforts through the Research Working Group of the Persian Gulf Veterans Coordinating Board, chaired by the secretaries of Defense, HHS, and VA. Yearly reports of activity have been submitted to Congress. Much has been learned, but much remains to be accomplished.

The Committee on Measuring the Health of Gulf War Veterans believes that the recommendations in this report will contribute answers to many of the remaining questions. We must learn the extent of the health problems experienced by Gulf War veterans, both those using the DoD and VA health systems and those seeking health care in the private sector. We must also ascertain how and in what ways the health problems of Gulf War veterans differ from those of the general public and other veterans groups. We must determine how the health status of all these groups changes through time, thereby enabling us to understand whether and to what extent Gulf War veterans differ from other groups. The prospective cohort study designed by the committee will provide the basis for answering these fundamental questions.

Additionally, given the enormous amount of time, effort, and resources devoted to numerous studies of the health of Gulf War veterans, it is important that a mechanism be implemented to allow comparisons across these studies on key health correlates and health outcomes. The research portfolio recommended by the committee is designed to accomplish this.

Finally, to assure the public, the veterans, Congress, the scientific community, and others that all efforts to resolve these issues are being conducted with

the greatest scientific integrity and public accountability, the committee believes it is necessary to establish an independent advisory board to oversee the implementation of the prospective cohort study and related research portfolio, with periodic reports on these efforts to Congress.