European Journal of Epidemiology

, Volume 23, Issue 2, pp 79–87 | Cite as

Prior health care utilization as a potential determinant of enrollment in a 21-year prospective study, the Millennium Cohort Study

  • Timothy S. Wells
  • Isabel G. Jacobson
  • Tyler C. Smith
  • Christina N. Spooner
  • Besa Smith
  • Robert J. Reed
  • Paul J. Amoroso
  • Margaret A. K. Ryan
  • For the Millennium Cohort Study Team


Results obtained from self-reported health data may be biased if those being surveyed respond differently based on health status. This study was conducted to investigate if health, as measured by health care use preceding invitation, influenced response to invitation to a 21-year prospective study, the Millennium Cohort Study. Inpatient and outpatient diagnoses were identified among more than 68,000 people during a one-year period prior to invitation to enroll. Multivariable logistic regression defined how diagnoses were associated with response. Days spent hospitalized or in outpatient care were also compared between responders and nonresponders. Adjusted odds of response to the questionnaire were similar over a diverse range of inpatient and outpatient diagnostic categories during the year prior to enrollment. The number of days hospitalized or accessing outpatient care was very similar between responders and nonresponders. Study findings demonstrate that, although there are some small differences between responders and nonresponders, prior health care use did not affect response to the Millennium Cohort Study, and it is unlikely that future study findings will be biased by differential response due to health status prior to enrollment invitation.


Cohort studies Military medicine Military personnel Response bias Veterans 



Confidence interval


International Classification of Diseases, Ninth Revision, Clinical Modification


Odds ratio



We are indebted to the Millennium Cohort Study participants, without whom these analyses would not be possible. We thank Scott L. Seggerman from the Management Information Division, Defense Manpower Data Center, Seaside, California. Additionally, we thank Laura Chu, MPH; Lacy Farnell; Gia Gumbs, MPH; Cynthia LeardMann, MPH; Travis Leleu; Steven Spiegel; Damika Webb; Keri Welch, MA; and Jim Whitmer from the Department of Defense Center for Deployment Health Research, Naval Health Research Center, San Diego, California; and Michelle Stoia, also from the Naval Health Research Center. We appreciate the support of the Henry M. Jackson Foundation for the Advancement of Military Medicine, Rockville, Maryland.


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Copyright information

© Springer Science+Business Media B.V. 2008

Authors and Affiliations

  • Timothy S. Wells
    • 1
  • Isabel G. Jacobson
    • 2
  • Tyler C. Smith
    • 2
  • Christina N. Spooner
    • 2
  • Besa Smith
    • 2
  • Robert J. Reed
    • 2
  • Paul J. Amoroso
    • 3
  • Margaret A. K. Ryan
    • 2
  • For the Millennium Cohort Study Team
    • 4
  1. 1.Biomechanics Branch, Air Force Research LaboratoryWright-Patterson Air Force BaseDaytonUSA
  2. 2.Department of Defense Center for Deployment Health ResearchNaval Health Research CenterSan DiegoUSA
  3. 3.Madigan Army Medical CenterTacomaUSA
  4. 4.San DiegoUSA

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