Association of Elevated Body Mass Index with Functional Outcome and Mortality following Acute Ischemic Stroke: The Obesity Paradox Revisited

Previous literature has identified a survival advantage in acute ischemic stroke (AIS) patients with elevated body mass indices (BMIs), a phenomenon termed the "obesity paradox."The aim of this study was to evaluate the independent association between obesity and clinical outcomes following AIS.Weighted discharge data from the National Inpatient Sample were queried to identify AIS patients from 2015 to 2018. Multivariable logistic regression and Cox proportional hazards modeling were performed to evaluate associations between obesity (BMI ≥ 30) and clinical endpoints following adjustment for acute stroke severity and comorbidity burden.Among 1,687,805 AIS patients, 216,775 (12.8%) were obese. Compared to nonobese individuals, these patients were younger (64 vs. 72 mean years), had lower baseline NIHSS scores (6.9 vs. 7.9 mean score), and a higher comorbidity burden. Multivariable analysis demonstrated independent associations between obesity and lower likelihood of mortality (adjusted odds ratio [aOR] 0.76, 95% confidence interval [CI]: 0.71, 0.82, p < 0.001; hazard ratio 0.84, 95% CI: 0.73, 0.97, p = 0.015), intracranial hemorrhage (aOR 0.87, 95% CI: 0.82, 0.93, p < 0.001), and routine discharge to home (aOR 0.97, 95% CI: 0.95, 0.99; p = 0.015). Mortality rates between obese and nonobese patients were significantly lower across stroke severity thresholds, but this difference was attenuated among high severity (NIHSS > 20) strokes (21.6% vs. 23.2%, p = 0.358). Further stratification of the cohort into BMI categories demonstrated a "U-shaped" association with mortality (underweight aOR 1.58, 95% CI: 1.39, 1.79; p < 0.001, overweight aOR 0.64, 95% CI: 0.42, 0.99; p = 0.046, obese aOR 0.77, 95% CI: 0.71, 0.83; p < 0.001, severely obese aOR 1.18, 95% CI: 0.74, 1.87; p = 0.485). Sub-cohort assessment of thrombectomy-treated patients demonstrated an independent association of obesity (BMI 30-40) with lower mortality (aOR 0.79, 95% CI: 0.65, 0.96; p = 0.015), but not with routine discharge.This cross-sectional analysis demonstrates a lower likelihood of discharge to home as well as in-hospital mortality in obese patients following AIS, suggestive of a protective effect of obesity against mortality but not against all poststroke neurological deficits in the short term which would necessitate placement in acute rehabilitation and long-term care facilities.