The Effect of Body Mass Index on Outcome after Endovascular Treatment in Acute Ischemic Stroke Patients: A Post Hoc Analysis of the MR CLEAN Trial

Abstract

Background: Though obesity is a well-known risk factor for vascular disease, the impact of obesity on stroke outcome has been disputed. Several studies have shown that obesity is associated with better functional outcome after stroke. Whether obesity influences the benefit of endovascular treatment (EVT) in stroke patients is unknown. We evaluated the association between body mass index (BMI) and outcome in acute ischemic stroke patients with large vessel ­occlusion (LVO), and assessed whether BMI affects the ­benefit of EVT. Methods: This is a post hoc analysis of the Multicenter Randomized Clinical Trial of Endovascular Treatment for Acute Ischemic Stroke in the Netherlands trial (­ISRCTN10888758). BMI was used as a continuous and categorical variable, distinguishing underweight and normal weight (BMI <25), overweight (BMI 25–30), and obesity (BMI ≥30). We used multivariable ordinal logistic regression analysis to estimate the association of BMI with functional outcome (shift analysis), assessed with modified Rankin Scale (mRs) at 90 days. The impact of BMI on EVT effect was tested by the use of a multiplicative interaction term. Results: Of 366 patients, 160 (44%) were underweight or normal weight, 145 (40%) overweight, and 61 (17%) were obese. In multivariable analysis with BMI as a continuous variable, we found a shift toward better functional outcome with higher BMI (mRS adjusted common OR 1.04; 95% CI 1.0–1.09), and mortality was inversely related to BMI (aOR 0.92; 95% CI 0.85–0.99). Safety analysis showed that higher BMI was associated with lower risk of stroke progression (aOR 0.92, 95% CI 0.87–0.99). Additional analysis showed no interaction between BMI and EVT effect on functional outcome, mortality, and other safety outcomes. Conclusion: Our study confirms the effect of obesity on outcome in acute ischemic stroke patients with LVO, meaning better functional outcome, lower mortality, and lower risk of stroke progression for patients with higher BMI. As we found no interaction between BMI and EVT effect, all BMI classes may expect the same benefit from EVT.