Those questions and more may be answered by a new joint-service Millenium Cohort Study headed by Navy doctor Lt. Cmdr. Margaret A.K. Ryan, director of the DoD Center for Deployment Health Research at the Naval Health Research Center in San Diego.

The 21-year-long project will be the most ambitious study of military personnel ever undertaken, Ryan said. Investigators will track 100,000 military people through health surveys mailed every three years. Of the 100,000 members, 70,000 will be veterans and active-duty members who have not served in Southwest Asia, Bosnia or Kosovo since 1997. The other 30,000 will be military people who served in these areas after Jan. 1, 1998.

The study will "over sample" reservists and female service members to get additional information on their health risks as increasing numbers are them are being deployed, she explained.

"The study will focus on determining if military service, especially deployments, puts military members at risk for disease," said Ryan. "We’ll examine military members’ incidence of chronic disease such as cancer, heart disease and diabetes."