The Millennium Cohort Study, which was launched in 2001 to help address health outcomes related to Service members' deployments, will soon be increasing its enrollment to more than 200,000 participants.
The next survey cycle, which begins this year, will add 50,000 new Cohort members plus 10,000 spouses of Service members to the study. "Surveying family members is difficult and new," said the cohort study's principal investigator Dr. Tyler C. Smith, MS, PhD, Director of the DoD Center for Deployment Health Research at the Naval Health Research Center in San Diego.
The cohort study originally enrolled a three-panel sample of about 152,000 military personnel representing all of the Services, including active duty and Reserve/Guard members. Participants agreed to provide important and secure information about their deployment exposures and health conditions throughout their service time and beyond, for up to 21 years. The study oversampled for Reserve/National Guard members, women, and those who had deployed to Southwest Asia, Kosovo and Bosnia (1998 and 2000) in order to ensure sufficient power to detect differences in smaller subgroups.
Dr. Smith provided an update on the cohort study before a group of military and veterans service organizations (MSO/VSO) at the FHP&R offices in Falls Church, Va., in late February. He explained that the need for such a study arose out of lessons learned and research gaps stemming from the 1991 Gulf War. "The Institute of Medicine recommended this type of longitudinal study, it was put into legislation, and DoD in a short amount of time launched this large-scale study to measure health of service members over their career and post military service," he said.
Dr. Smith said more than half of the original Cohort participants have deployed in support of OEF/OIF in the last nine years since the research began in the summer of 2001 before 9/11. The key aspect of the study is that it established their pre-deployment baseline health measures and is examining the impact of their deployment exposures on health outcomes, including subjective measures of physical and mental health and objective measures of diseases, mortality, and vaccinations. "What we have consistently found is that our military members are healthy and our deploying members are selectively healthier, but there are exposures in theater such as combat exposures that are impacting post deployment health," Dr. Smith advised.
The cohort study includes survey questions about alcohol use, smoking, sleep, exercise, complementary and alternative medicine use, supplement use, occupation, vaccinations, deployment exposures, mental and physical health, and behavioral health. "We've added questions to assess reproductive outcomes, resiliency, injuries, and have linked to military trauma registries and the DoD Birth and Infant Health Registry (greater than 900,000 babies of Service members that tracks birth defects and other infant health outcomes)," Dr. Smith said. "The key to answering veteran and public health concerns is to understand baseline health, and to follow that forward while differentiating between deployment and other military occupational exposures in order to quantify any health impact from military service. Though we report our findings early at military and scientific conferences, publishing in high-level peer-reviewed journals gives our research credibility in the science community and puts us on par with important academic levels of scientific quality. This also allows the findings to be more widely available to both clinicians and policymakers."
Following many validation and foundation papers published in 2007, the second round of Cohort studies were published in 2008-09. One showed for the first time a 2-3 times risk of new onset and persistent PTSD symptoms among deployed Service members who were exposed to combat compared to those who did not deploy or who deployed but were not exposed to combat. [In the February 2008 British Medical Journal, Millennium Cohort Study researchers wrote that self-reported PTSD symptoms or diagnoses were about five times higher in Service members who deployed to Iraq or Afghanistan and were exposed to combat exposures, which include witnessing death, trauma, injuries, prisoners of war, or refugees, compared to deployers not exposed to combat.]
"This was a crucial finding because it differentiated new onset PTSD symptoms from persistent or chronic symptoms and highlighted the impact of combat experiences on the PTSD symptoms rather than deployment in general," Dr. Smith said.
An audience member at February's MSO/VSO meeting added that the increase in multiple deployments among Reserve and Guard members may also cause stress in deployers who may have the feeling of "waiting to be attacked" while in the field. They may be at increased risk of alcohol abuse, post-deployment, for example. "We conjecture that when they go home away from their units and back to their families there can be issues with the transition," Dr. Smith said.
Sure enough, in the Aug. 13, 2008 Journal of the American Medical Association, Cohort researchers found that Reserve/National Guard members and younger active duty Service members who reported being exposed to combat during deployments to Iraq or Afghanistan are at increased risk of new-onset heavy weekly drinking, binge drinking and alcohol-related problems compared to those who deployed, but reported no combat exposures. In the December 2008 issue of the American Journal of Preventive Medicine the Cohort study also showed that deployments to Iraq or Afghanistan especially prolonged ones, multiple deployments or those with combat exposures, lead Service members to start smoking or previous smokers to resume the habit.
Latest Round of Studies
One of the most recent papers to arise from the Millennium Cohort Study examines newly reported hypertension following combat deployment, while another investigates respiratory symptoms among military personnel who have deployed on-land to Iraq or Afghanistan. A third paper (British Medical Journal, April 2009) shows that Service members who were in poor functional health to begin with were at a greater risk of PTSD after deployment, illustrating the need for pre-deployment resiliency training among certain groups.
In the study that appeared in Hypertension on September 14, 2009 and was led by Dr. Nisara Granado, deployers who reported multiple combat exposures were 1.33 times more likely to experience hypertension compared with noncombat deployers, signaling that such high stress situations can be a potential risk factor for the disorder. Meanwhile another paper led by Dr. Besa Smith in the October 22, 2009 American Journal of Epidemiology showed higher rates of respiratory outcomes due to a higher occurrence of persistent and recurring cough among Army and Marine Corps personnel who deployed on land to Iraq and Afghanistan and recurring shortness of breath among Army personnel, but no increased risk of such symptoms in Air Force or Navy personnel. Dr. Smith highlighted the need for additional research that focuses on in-theater exposures, such as the open air trash burning pits and particulate matter exposures, and a follow-up of those with increased symptom reporting to see if the symptoms were transient or progressed into chronic illness.
An audience member also expressed concern that the number of Reserve forces with severe exposures to trauma from the OEF/OIF war theater who are treated in Landstuhl Regional Medical Center in Germany, for example, may put military healthcare providers there at risk for mental health issues after a while because of the high amount of trauma they see and attend to. "What we found with deployed caregivers is that there may be an increase in depression post-deployment, but that trend does not look consistent with PTSD symptoms," Dr. Smith advised.
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