Supplementary Material for: Body mass index and outcomes in patients with Takotsubo syndrome: a nationwide retrospective cohort study

Background: 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.
Methods: Using the Japanese Diagnosis Procedure Combination database, we retrospectively identified 14,551 patients admitted for TTS between 2010-2021. By applying multivariable regressions with restricted cubic splines, we examined the association between BMI and in-hospital mortality after adjusting for potential confounders.
Results: Mean BMI was 21.1 kg/m2, classifying patients into severe underweight (<16.0 kg/m2, 7.1%), mild/moderate underweight (16.0-18.4 kg/m2, 18.3%), normal weight (18.5-22.9 kg/m2, 46.8%), overweight (23.0-27.4 kg/m2, 22.2%), and obese (≥27.5 kg/m2, 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% CI=1.54-2.73]) and mild/moderate underweight (1.26 [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/m2 but nearly plateauing in BMI >20 kg/m2.
Conclusions: 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.