Cause and Effect

The Millennium Cohort Study focuses on the long-term health-care consequences of deployment.

Agent Orange in Vietnam. Pills intended to protect troops against nerve-gas attacks in the Gulf War. Burn pits to dispose of military waste in Iraq.

Thousands of Americans have gone off to war and returned with ailments they suspect were caused by these or other exposures they liken to friendly fire – conditions caused by routine wartime service rather than enemy attack.

The true causes of many war-based ailments remain elusive, even after billions of dollars in federal research and years of investigation have been exhausted on the matter. The fact remains that precious little information is available to connect the dots between armed service and the effects that often follow later in life.

Since 2001, the Department of Defense has been conducting a large-scale, long-term study of military personnel and veterans to help close the information gap. The Millennium Cohort Study (MCS) randomly selected the first of what were eventually about 150,000 participants from all service branches, the National Guard and the reserves, asking them to answer health-related questionnaires once every three years over a span of 21 years. Of those invited to join the cohort, 36 percent agreed to participate.

MCS participants have the option to respond by mail or online, and 88 percent chose to do so online in the most recent response. Along with their questionnaires, additional information is gathered by linking to health-related databases such as inpatient and outpatient information from both military and civilian facilities, and exposure and disability data.

The study is conducted from DoD’s Center for Deployment Health Research, located at the Naval Health Research Center in San Diego. The MCS team is working with VA, along with British researchers who have undertaken a similar study of their country’s military personnel.

Thus far, the MCS has been the basis for about 30 peer-reviewed publications and 150 scientific presentations. These findings indicate that servicemembers exposed to combat in Iraq or Afghanistan are at a higher risk for some health problems, including high blood pressure, respiratory symptoms, post-traumatic stress disorder (PTSD), and increased smoking and alcohol use. Some subgroups appear to be more vulnerable to these risks than others, and the hope is that the study will help target such individuals for intervention to prevent adverse effects.

Unlike previous studies of U.S. military personnel, the MCS is a “prospective cohort study” following a group of similar individuals over time to determine how various factors might affect outcomes. The timing of the study, which began enrolling participants just months before 9/11, allows researchers to examine the effects among those deployed in the war on terror before, during and after they went. That’s important, since many veterans claim to have not experienced problems until years after they returned home. Some Vietnam War veterans, for example, didn’t suffer from PTSD until 10 to 15 years after discharge.

With that long-term focus, veterans participating in the study are playing a vital role in the search for answers.

“Continued participation, even after separation from military service, is critical to understanding any long-term health effects that may be associated with military service and deployment,” says Dr. Tyler Smith, the MCS’ principal investigator. About 20 percent of cohort participants have since been discharged from the military.

The catalyst for the Millennium Cohort Study was complaints among veterans that deployments in the 1991 Gulf War may have led to long-term health problems. In response, the Institute of Medicine urged that a study be undertaken, Congress authorized it, and the project had this stated objective: “Determine how the health of U.S. military servicemembers and veterans changes over time, and determine the health impact of military deployments/exposures upon the adjusted incidence of chronic disease.”

“We’ll examine military members’ incidence of chronic diseases such as cancer, heart disease and diabetes,” Dr. Margaret Ryan, former principal investigator of the study, said in 2001.

But the questionnaire has only one question with an open-ended box involving cancer. There is nothing on neurological problems or heart problems, except high blood pressure.

In fact, most of the published studies are related to psychological and behavioral conditions rather than physical problems, even though those complaining of Gulf War illnesses had charged that past DoD studies were too quick to point to stress as the cause of their mysterious maladies.

“Study choices to date have been chosen based on the requirements, needs and concerns of veterans, providers and leadership in DoD and VA,” Smith explained. “Because of the longitudinal design of the Millennium Cohort Study, broad assessments of rare outcomes like cancer were not included early on, though they will be expanded on in later questionnaires as the cohort ages.”

He adds that other studies are under way,  with focuses on cancer, heart disease, auto-immune disorders and chronic multisymptom illness. Future research will include neurological testing.

In the past nine years, thousands of military servicemembers and veterans have taken the time to fill out MCS questionnaires. About 77,000 enrolled in the cohort’s first phase, beginning in July 2001. More than 30 percent had been deployed. About 31,000 more enrolled in 2004, and 40,000 more in 2007. Plans call for adding 60,000 more this year. About 70 percent of those in the cohort have provided at least one follow-up response. More than half have deployed since 2001.

Additional responses on the impact of military service and deployment on family health are to be gathered during the 2010-2011 survey cycle. An estimated 10,000 spouses are expected to enroll, about half of whose husbands or wives will be, or will have been, deployed at least once to Iraq or Afghanistan.

With so many responses, the MCS is one of the largest cohort studies in military history, but few seem to be aware of it.

“There needs to be greater outreach,” says  Joe Sharpe, director of The American Legion’s Economic Division and the Legion’s representative on the MCS Scientific Steering and Advisory Committee. Sharpe calls the study’s preliminary data “fascinating,” but says  he would like to see more published findings.

Existing and future MCS studies offer the promise of a better understanding of the health effects of deployments and the resulting possibility of improving the health of past, current and future military personnel.

“We try to transition this data into real-world benefits for the servicemembers,” Smith says. “Participants should feel confident that they are contributing to an effort of profound public-health importance.”

Margaret Davidson is a freelance writer who specializes in covering medical issues.

 

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