Complex Comorbidity Clusters in OEF/OIF Veterans: The Polytrauma Clinical Triad and Beyond

Background: A growing body of research on US Veterans from Afghanistan and Iraq [Operations Enduring and Iraqi Freedom, and Operation New Dawn (OEF/OIF)] has described the polytrauma clinical triad (PCT): traumatic brain injury (TBI), posttraumatic stress disorder (PTSD), and pain. Extant research has not explored comorbidity clusters in this population more broadly, particularly co-occurring chronic diseases. Objectives: The aim of the study was to identify comorbidity clusters among diagnoses of deployment-specific (TBI, PTSD, pain) and chronic (eg, hypertension, diabetes) conditions, and to examine the association of these clusters with health care utilization and adverse outcomes. Research Design: This was a retrospective cohort study. Subjects: The cohort comprised OEF/OIF Veterans who received care in the Veterans Health Administration in fiscal years (FY) 2008–2010. Measures: We identified comorbidity using validated ICD-9-CM code–based algorithms and FY08–09 data, followed by which we applied latent class analysis to identify the most statistically distinct and clinically meaningful patterns of comorbidity. We examined the association of these clusters with process measures/outcomes using logistic regression to correlate medication use, acute health care utilization, and adverse outcomes in FY10. Results: In this cohort (N = 191,797), we found 6 comorbidity clusters. Cluster 1: PCT + Chronic Disease (5%); Cluster 2: PCT (9%); Cluster 3: Mental Health + Substance Abuse (24%); Cluster 4: Sleep, Amputation, Chronic Disease (4%); Cluster 5: Pain, Moderate PTSD (6%); and Cluster 6: Relatively Healthy (53%). Subsequent health care utilization patterns and adverse events were consistent with disease patterns. Conclusions: These comorbidity clusters extend beyond the PCT and may be used as a foundation to examine coordination/quality of care and outcomes for OEF/OIF Veterans with different patterns of comorbidity.