A study of more than 250,000 service members begun in 2001 released some preliminary findings on Friday, to celebrate the effort’s 20th anniversary.

Among them is that a plurality of male troops and veterans report tinnitus, or ringing of the ears, as their No. 1 health complaint. For women, the biggest issue is depression, though among women in the reserve component, migraines slightly edge out depression.

The Millennium Cohort Study, inspired by concerns about the health effects of serving in Vietnam and the Gulf War, began in 2001 and has enrolled new waves of subjects every few years.

“The goal of the study is to understand the impact of military service, including deployments and other occupational exposures, on the long-term physical health, mental health, and quality of life of service members,” according to a report released Friday, which presents data from 2001 to 2016.

One of the principal findings is top health concerns among troops. Among men, 24 percent report tinnitus, 23 percent report high blood pressure, 20 percent high cholesterol, 17 percent sleep apnea and 17 percent acid reflux. Those levels are roughly the same for active-duty and reserve troops, as well as veterans.

The top concerns are different for women: 25 percent report depression, 24 percent migraine, 18 percent sinusitis, 17 percent acid reflux and 14 percent tinnitus.

For the reserve component, migraines came in at 18 percent, with depression at 15 percent.

The study also took a specific look at deployments and how they affect health. It did not compare the findings against the civilian population.

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“A 2013 study from the Millennium Cohort Team showed that combat-related trauma and pre-deployment insomnia symptoms were significantly associated with developing post-traumatic stress disorder, depression, and anxiety following deployment at 3-year follow-up,” according to the report.

Data is also organized by health markers, like getting enough sleep, maintaining a healthy weight and not smoking, and compares them against outcomes.

“We followed participants from their first survey for 3-12 years afterwards, to look at patterns of continued unhealthy alcohol use [defined as heavy weekly, heavy episodic, and problem drinking (an assessment of consequences related to drinking too much)],” according to the report. “Our findings showed that among those who were unhealthy alcohol users at their first survey, 70 percent continued unhealthy use at their follow-up surveys, around 3- 5 years later, which suggests chronic use.”

For all of the services, including the Coast Guard, the percentage of study participants who quit smoking went up over the course of the study, despite the fact that deployments were associated with picking up tobacco use.

But the percentage who got enough sleep ― between seven to nine hours a night ― and who stayed at a healthy weight went down.

“Participants who were normal weight, never/former smoker, or who did not report depression were more likely to meet physical activity guidelines,” according to the report.

And, by the same token, subjects who stayed away from tobacco products, got enough sleep and exercised regularly were less likely to become overweight.

Ongoing results of the study have also been folded into other research and initiatives. In 2020, the National Defense Authorization Act called for MCS to work up an annual report about gynecological and perinatal health in troops and veterans.

The congressionally mandated study will continue through 2068.