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VA Cooperative Studies Program (CSP)

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CSP #505: Millennium Cohort Study


Investigator Access

What's Available

Research data

  • Questionnaire data: Self-reported, individual participant data collected during the 5 survey cycles (2001, 2004, 2007,2011, 2014). (SAS format)
  • Department of Defense records: Defense Manpower Data Center (DMDC) electronic military personnel data, and Military Health System Data Repository (MDR) data. (SAS format)
  • VA records: Electronic health, benefits, and disability records (EHR) on all Millennium Cohort Study participants who have VA records. (SAS format, available mid-2019)
  • Millennium Cohort study data is distinct from VA Electronic Health Record (EHR) Modernization data. Researchers can contact the VA Information Resource Center (VIReC) for information about EHR modernization data.

Available Documentation 

Dates Data are Available 

  • Questionnaire data: Currently available, no end date
  • DoD records: Currently available, no end date
  • VA records: Currently available, no end date

Access Criteria 

VA investigators: To request access to data, interested VA investigators should submit a Research Resource Request form to the CSP #505 Project Manager at Investigators whose request forms are approved by CSP #505 and Naval Health Research Center (NHRC) are invited to submit a Secondary Data Analyses Proposal. The Secondary Data Analyses Proposal will be reviewed by VA’s CSP #505 Executive Committee and NHRC’s Millennium Cohort Study Scientific Review Committee. For approved proposals, the VA investigator will scientifically lead the project and paper, while data analyses may be performed in one of the following ways:

  1. Analyses performed at NHRC by NHRC study staff under the direction of VA investigator

      a. VA investigator doesn’t have direct access to the individual-level data
      b. Might not require a Data Use Agreement (DUA) between CSP #505 and the VA investigator’s institution

  2. Analyses performed at VA by VA investigator/investigator’s data manager/analyst 

      a. VA investigator has direct access to the individual-level data
      b. DUA required between CSP #505 of the VA investigator’s institution
      c. VA investigator must be capable of performing data management activities and analyses, or providing their own data manager/analyst

Non-VA investigators: : Non-VA investigators may also submit a Research Resource Request form to the CSP #505 Project Manager at Approved request forms will be invited to submit a Secondary Data Analyses Proposal template which must be approved by the CSP #505 Executive Committee and the Naval Health Research Center (NHRC) Scientific Review Committee. Visit Research Collaborations1 study webpage or contact for more information. 

Study Characteristics


This study investigates the long-term health effects of military service by capturing the entirety of the military life cycle from entry into service to transition back into civilian life as a Veteran. The cohort now includes more than 200,000 servicemembers, 70% of which are Veterans. The original objectives included building a cohort of ~150,000 and assessing chronic diagnosed and subjective health problems among military members, in relationship to exposures of military concern.

Era of Service

Primarily Gulf War, Operation Enduring Freedom (OEF), Operation Iraqi Freedom (OIF), Operation New Dawn (OND)


U.S. military personnel (active duty, Reserves, and National Guard) serving in the Army, Navy, Coast Guard, Air Force, and Marine Corps from October 1, 2000 - present.

As of 2017, 31% of Millennium Cohort Study participants identified as female and 70% identified as non-Hispanic white. Approximately 47% of participants were current or former members of the Army, 29% Air Force, 19% Navy/Coast Guard, and 5% Marine Corps; 70% of survey participants were Veterans.

Study Design 

Prospective cohort 

Time Period 

2001 - 2068

Participants surveyed every 3-5 years over a 67-year period.


National and international


≥200,000 for all 4 panels enrolled in 2001, 2004, 2007, and 2011

Response Rate

  2001 2004 2007 2011 2014 
Panel 1 77,047 (35.9%) 55,021 (71.4%) 54,790 (71.1%) 51,678 (67.1%)

 51,156 (68.4%)

Panel 2 N/A 31,110 (21%) 17,152 (55.1%) 15,149 (48.7%)  14,800 (48.2%)
Panel 3 N/A N/A 43,439 (22%) 22,071 (50.8%)  20,000 (46.4%)
Panel 4 N/A N/A N/A 50,052 (20%)  27,236 (54.5%)

A new data collection cycle began in 2019.  Those data will be collected through 2020, and possibly into 2021.

Panel 5 is beginning enrollment in August 2020. More information on study panels can be found at (Recommend viewing with a browser other than Internet Explorer)

Recruitment Method    

A probability-based sample of active-duty, Reserve, and National Guard members from all services was constructed by the DMDC. Individuals are contacted via mail or email and invited to complete a study questionnaire either on the paper copy received in the mail or through the online version. A modified-Dillman approach is implemented using mailed postcard and email reminders to increase response rate among participants.


Nominal incentives provided (variable over time) with maximum value of $5 in form of t-shirt, coin, hat, or gift card.

Data Collected

  • Demographic and military-specific data obtained from electronic personnel files maintained by DMDC
  • Study questionnaire1 collects data on a broad range of topics such as general health, health behaviors, health conditions/symptoms, health care utilization, military and combat history, and potential exposures.

Data Collection Methods

Survey data collected via structured questionnaire, mailed or online, with linkage to medical records and other databases for active duty personnel (e.g., inpatient, outpatient, pharmaceuticals, vaccination information, and mortality data) and with linkage to VA records for separated personnel in the VA system.

Funding Sources

Department of Defense through the Defense Health Board


Principal Investigator: Rudy Rull, PhD, MPH
Study Chair: Edward J. Boyko, MD, MPH


CSP #505 Project Manager:
CSP #505 Study Chair:

Selected Publications

Gray GC, Chesbrough KB, Ryan MA, Amoroso P, Boyko EJ, Gackstetter GD, Hooper TI, Riddle JR; Millennium Cohort Study Group. The millennium Cohort Study: a 21-year prospective cohort study of 140,000 military personnel. Mil Med. 2002 Jun;167(6):483-8.

Smith TC, Millennium Cohort Study Team. The US Department of Defense Millennium Cohort Study: career span and beyond longitudinal follow-up. J Occup Environ Med. 2009 Oct;51(10):1193-201.

Crum-Cianflone NF, Naval Health Research Center San Diego CA. The Millennium Cohort Study: Answering Long-Term Health Concerns of US Military Service Members by Integrating Longitudinal Survey Data with Military Health System Records. Part 2. Pre-Deployment. 2013 Jan. 

Belding JN, Castañeda SF, Jacobson IG, LeardMann CA, Porter B, Powell TM, Kolaja CA, Seelig AD, Matsuno RK, Carey FR, Rivera AC, Trone DW, Sheppard BD, Walstrom JL, Boyko EJ, Rull RP, Millennium Cohort Study Team. The Millennium Cohort Study: The first 20 years of research dedicated to understanding the long-term health of US Service Members and Veterans. Ann Epidemiol. 2022 Mar;67:61-72. doi: 10.1016/j.annepidem.2021.12.002. 

Additional publications(Recommend viewing with a browser other than Internet Explorer)

More Information

Millennium Cohort study website(Recommend viewing with a browser other than Internet Explorer)

August 2018 VA Research Currents newsletter article: Data-sharing milestone


1 This link takes you to a non-U.S. government website. VA isn't responsible for the content or privacy policies on that site and doesn't endorse the content or its sponsor.