Body Mass Index and Outcomes in Patients with Takotsubo Syndrome: A Nationwide Retrospective Cohort Study

Abstract

<b><i>Background:</i></b> Takotsubo syndrome (TTS) is a cardiac disorder that mimics acute coronary syndrome at presentation. While previous studies have demonstrated a relationship between body mass index (BMI) and outcomes in acute coronary syndrome, few have examined its relationship with TTS. <b><i>Methods:</i></b> Using the Japanese Diagnosis Procedure Combination database, we retrospectively identified 14,551 patients admitted for TTS between 2010 and 2021. By applying multivariable regressions with restricted cubic splines, we examined the association between BMI and in-hospital mortality after adjusting for potential confounders. <b><i>Results:</i></b> Mean BMI was 21.1 kg/m<sup>2</sup>, classifying patients into severe underweight (<16.0 kg/m<sup>2</sup>, 7.1%), mild/moderate underweight (16.0–18.4 kg/m<sup>2</sup>, 18.3%), normal weight (18.5–22.9 kg/m<sup>2</sup>, 46.8%), overweight (23.0–27.4 kg/m<sup>2</sup>, 22.2%), and obese (≥27.5 kg/m<sup>2</sup>, 5.6%) groups. Patients with severe or mild/moderate underweight were older and had a higher prevalence of impaired physical activity, malignancy, chronic pulmonary disease, and pneumonia. In-hospital mortality was the highest (9.4%) in the severe underweight group, followed by the mild/moderate underweight group (5.4%), with the lowest being in the obese group (2.1%). Severe underweight (adjusted odds ratio = 2.05; 95% confidence interval [CI] = 1.54–2.73) and mild/moderate underweight (1.26; 95% CI = 1.01–1.57) were significantly associated with higher mortality compared with normal weight, while no significant association was noted with obesity. A nonlinear association between continuous BMI and mortality was observed, with mortality increasing when BMI decreased <20.0 kg/m<sup>2</sup> but nearly plateauing in BMI >20.0 kg/m<sup>2</sup>. <b><i>Conclusions:</i></b> The present nationwide analysis demonstrated a nonlinear association between BMI and in-hospital mortality of TTS. BMI is an easily available and clinically relevant marker for the risk stratification of TTS.