Application of a New Method for Linking Anonymous Survey Data in a Population of Soldiers Returning from Iraq

PurposeThis study provides a unique application of a procedure to link anonymous survey records as a means to assess mental health problems among soldiers after return from deployment to Iraq. The research purpose is to validate the use of a linkage method on anonymous survey data for longitudinal analysis.MethodsThis research analyzes surveys completed by soldiers at three (N = 4,903), six (N = 3,110), and 12 (N = 2,544) months post–Operation Iraqi Freedom (OIF) deployment. To protect anonymity while also allowing for longitudinal analysis, the survey includes four self-generated codes for matching the surveys from individual soldiers. The surveys were linked using Link Plus (Centers for Disease Control and Prevention, Atlanta, GA). Three matched groups (3–6 months, 6–12 months, and 3–12 months) were created, matching on the anonymous codes and demographic variables. An internal validation of the linkage results was performed and selection bias was assessed.ResultsThe matched records showed very high agreement in variables not included in the matching procedure and were similar to the unmatched records with regard to demographics and post-traumatic stress disorder (PTSD) prevalence.ConclusionsThe use of self-generated codes protects anonymity while the method utilized and validated in this paper allows for longitudinal data analysis. The results support an absence of any notable selection bias.