What We Can Learn in 21 Years

The DoD and VA have formed an aggressive partnership to care for Operation Enduring Freedom and Operation Iraqi Freedom service members who have become wounded, ill or injured. Thanks to this partnership, the medical issues these servicemembers face are treated expediently, and their health status is consistently monitored by VA and DoD. But what is being done for those service-members who don’t develop medical problems until years after they’ve left the military? Often, they are left wondering if something that happened during their service could be responsible for illnesses and ailments that afflict them later in life. Sadly, veterans have had to contend with this issue for decades.

This concern became one of the medical lessons learned from the 1990-1991 Gulf War. In order to address this issue, the military services and the VA began working together in 1999 to design a prospective study that would evaluate the impact of military service on long-term health. Launched in the summer of 2001, the Millennium Cohort Study observes a population of randomly selected participants (active duty, Reserve and National Guard) who will complete health-related questionnaires every three years until 2022. An important caveat of the Millennium Cohort Study is that the information compiled is all self-reported by the individuals who are enrolled. Therefore, because the study relies on participants to accurately report their own symptoms or exposures, there are some limitations to its overall precision.

The researchers managing the Millennium Cohort Study at the Naval Health Research Center in San Diego, CA, are joined by investigators from each military service, the VA and academic research institutions. Through a series of regular questionnaires, researchers collect information about study participants’ physical and psychological health, use of complementary and alternative medicine, occupational exposures, smoking and drinking habits, and any health outcomes or symptoms they might be experiencing. Those enrolled are highly encouraged to continue participating in the study, even after leaving the military, so that the information will be as complete as possible. Just over 150,000 individuals currently participate in the study and in early 2010 an additional 50,000 service members will be invited to enroll. During 2010, participants will be asked to complete their fourth triennial questionnaire.

Although this is a long-term prospective study that will take 21 years to complete, its results are not being sealed in a time capsule until its completion in 2022. Results comparing non-deployed and deployed servicemembers, combat and non-combat veterans, active duty, Reserve and National Guard personnel, and men and women from all ethnicities and demographics are being regularly reported and are better informing DoD, VA and other medical providers on how to best care for those who are serving our nation. In fact, more than 30 publications of findings from the Millennium Cohort Study have already appeared in medical and scientific journals.

So far the study’s findings have given valuable insights into important issues including psychological health and substance abuse. For example, nearly 60% of those enrolled have served in a combat theater. Out of that number, those who have experienced combat have reportedly suffered from, or been diagnosed with, PTSD at rates of 10%. Alternatively, those who deployed but were not exposed to combat report PTSD at rates of 2%, while those who did not deploy report PTSD at rates of 5%. In addition, smoking has increased by 57% (17% at baseline to 26% at follow-up over three years) in deployed servicemembers and alcohol abuse was higher in those returning with combat experience, especially among Reserve and Guard members. Hypertension was a new finding in 7% returning from deployment. When asked about new symptoms of shortness of breath or persistent or recurring cough, some 14% of deployers and 10% of non-deployers answered positively. While these data cannot explain what caused the symptoms, they can guide further studies to do just that. These issues are critical to enabling DoD and VA to institute programs to educate and care for those individuals on their “journey home.”

Besides adding a new panel of service members to the Millennium Cohort Study in 2010, some 10,000 spouses of those already enrolled will be added to the cohort in order to assess the impact of military service on family members’ (spouses and coresident children) health and relationships. By adding spouses to the mix, the Millennium Cohort Study researchers are breaking new ground – this has never been done in a military research population.

Prospective cohort studies have provided medical science with valuable information that is not possible to develop while looking at individuals when they present with medical conditions. What we understand about heart disease risks is based, in large part, by the observational studies of the civilian population of Framingham, MA, over several decades. Conducting a prospective, 21-year study that begins with a military population that works in locations around the world and later becomes a part of our civilian community is a daunting task for the researchers working on the Millennium Cohort Study. But their success will come from the commitment of the study participants who realize that their continued involvement will provide the answers to many long-standing questions and will undoubtedly lead to new innovations to protect the long-term health of those who follow them in serving our nation in uniform.

By Dr Michel E. Kilpatrick

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