Obesity paradox in stroke - Myth or reality? A systematic review

Background and purpose Both stroke and obesity show an increasing incidence worldwide. While obesity is an established risk factor for stroke, its influence on outcome in ischemic stroke is less clear. Many studies suggest a better prognosis in obese patients after stroke ("obesity paradox"). This review aims at assessing the clinical outcomes of obese patients after stroke by performing a systematic literature search. Methods The reviewers searched MEDLINE from inception to December 2015. Studies were eligible if they included outcome comparisons in stroke patients with allocation to body weight. Results Twenty-five studies (299'750 patients) were included and none was randomised. Ten of 12 studies (162'921 patients) reported significantly less mortality rates in stroke patients with higher BMI values. Seven of 9 studies (92'718 patients) ascertained a favorable effect of excess body weight on non-fatal outcomes (good clinical outcome, recurrence of vascular events). Six studies (85'042 patients) indicated contradictory results after intravenous thrombolysis (IVT), however. Several methodological limitations were observed in major part of studies (observational study design, inaccuracy of BMI in reflecting obesity, lacking body weight measurement, selection bias, survival bias). Conclusion Most observational data indicate a survival benefit of obese patients after stroke, but a number of methodological concerns exist. No obesity paradox was observed in patients after IVT. There is a need for well-designed randomized controlled trials assessing the effects of weight reduction on stroke risk in obese patients.