Frailty score does not explain differences in mortality between underweight black and white veterans after stroke

Abstract

Background Previous studies suggest being underweight may increase risk of mortality after stroke. Paradoxically, in several studies of U.S. Veterans, black stroke patients have better survival compared to whites, even at lower body mass index (BMI). We hypothesized that frailty status may explain the observed differences. Methods A nationwide sample of Veterans hospitalized for first ischemic stroke in the Veterans Health Administration (VA) between 2002-2012 were studied. Veterans had a frailty index derived from the electronic health record and calculated on those over age 65 years. BMI (kg/m2) was calculated using VA outpatient measurements. Death was determined using the National Death Index. We grouped the cohort by race (non-Hispanic white, non-Hispanic black) and frailty status (frail, not frail). Hazard ratios (HRs) for mortality for eight BMI categories were estimated from Cox models with high normal BMI (22.5 Results There were 8,541 incident ischemic strokes; 1,772 were black veterans (21%) and 6,769 white veterans (79%). Average age and BMI were 76.4±7 years and 28.1±5.3 respectively. There were 5,697 deaths; 2,428 (43%) within one year after stroke and 1,025 (18%) within 30 days. Underweight non-frail and frail black veterans (BMI Conclusion Underweight white veterans have higher risk of 1-year mortality after stroke, despite frailty. The prevalence of AF between races may contribute to the increased risk for underweight white veterans, given that AF may cause more severe strokes. Factors contributing to higher mortality for underweight stroke patients likely include characteristics beyond frailty, including race and specific comorbidities.