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.