Sex-specific impact of mild obesity on the prognosis of ST-segment elevation myocardial infarction

This study aimed to clarify the existence of the mild obesity paradox in patients with ST-segment elevation myocardial infarction (STEMI) and assess the impact of mild obesity on the prognosis of STEMI. A retrospective cohort study was conducted on STEMI patients who underwent percutaneous coronary intervention at Xiangtan Central Hospital from January 1, 2020 to July 31, 2022. After excluding individuals with a body mass index (BMI) of no less than 35 kg/m 2 , subjects were divided into the mildly obese group (BMI, 30–35 kg/m 2 ) and non-obese group (BMI < 30 kg/m 2 ). The cardiovascular events and death were deemed the composite endpoints and were employed as the outcome event. The study recruited 664 patients with STEMI, including 515 males and 149 females. The mildly obese group of male patients exhibited a lower incidence of composite endpoints than the non-obese group (22.4% vs. 41.3%, P < 0.001). For female patients, no significant difference was observed in the incidence of composite endpoints between the two groups (43.6% vs. 43.8%, P = 0.987). After adjusting for confounding factors, the multivariable Cox regression analysis revealed mild obesity as an independent protective factor for male patients [hazard ratio (HR) 0.47; 95% confidence interval (CI) 0.32–0.69; P < 0.001]. Nevertheless, mild obesity was not associated with the prognosis of female patients (HR 0.96; 95% CI 0.47–1.94; P = 0.9). In male STEMI patients, mild obesity presented a paradoxical effect in improving the prognosis and functioned as an independent protective factor for the prognosis of STEMI. However, no association between mild obesity and prognosis was found in female patients, possibly due to distinct physiological and metabolic characteristics between male and female patients, which deserved further investigation and validation.