Abstract
BACKGROUND: Individuals who present with acute myocardial infarction in the absence of standard modifiable cardiovascular risk factors (ie, SMuRF-less) seem to have a significantly increased risk of mortality; however, it remains unclear whether the "SMuRF paradox" would be influenced by patients' baseline body mass index (BMI) status. METHODS: Using data from the CCC-ACS (Improving Care for Cardiovascular Disease in China-Acute Coronary Syndrome) project from November 2014 to July 2019, we analyzed patients with acute myocardial infarction with and without SMuRFs and categorized their BMI as underweight (<18.5 kg/m(2)), normal weight (18.5-24 kg/m(2)), overweight (24-28 kg/m(2)), and obese (>28 kg/m(2)). The primary outcome was in-hospital all-cause mortality. Multivariable logistic regression models were used to estimate BMI-stratified associations between SMuRF-less status and outcomes. RESULTS: The study included 44 538 patients with first-presentation acute myocardial infarction, of whom 4454 were SMuRF-less. The incidence of SMuRF-lessness declined from 16.2% to 6.5% as BMI increased by category, and it prevailed more frequently among women and older people regardless of their BMI status. Patients who were SMuRF-less had a significant increase in in-hospital mortality than patients with ≥1 SMuRF (adjusted odds ratio [OR], 1.750 [95% CI, 1.057-2.896], P<0.001). The highest mortality rate was observed in the group who were SMuRF-less and underweight (3.5%). Considering patients with ≥1 SMuRF and obesity as the reference group, the group who were SMuRF-less underweight exhibited the highest increase in mortality (adjusted OR, 3.854 [95% CI, 2.130-6.973], P<0.001). CONCLUSIONS: Among patients with first-presentation acute myocardial infarction, compared with those with ≥1 SMuRF, patients who were SMuRF-less have a significantly higher risk of in-hospital mortality, especially in those underweight, whereas in-hospital survival was the most favorable among patients with ≥1 SMuRF and obesity. REGISTRATION: URL: https://www.clinicaltrials.gov; Unique identifier: NCT0230661.