Number of standard modifiable risk factors and mortality in patients with first-presentation ST-segment elevation myocardial infarction: insights from China Acute Myocardial Infarction registry

Background Recent publications reported a paradoxical finding that there was an inverse association between the number of standard modifiable risk factors (SMuRFs; smoking, hypertension, diabetes, and hyperlipidemia) and mortality in patients with myocardial infarction. However, the current evidence is only limited to those highly developed countries with advanced medical management systems. Methods The China Acute Myocardial Infarction registry is a prospective observational study including patients with acute myocardial infarction from three-level hospitals across 31 administrative regions throughout mainland China. A total of 16,228 patients with first-presentation ST-elevation myocardial infarction (STEMI) admitted to hospitals from January 2013 to September 2014 were enrolled in the current analysis. Cox proportional hazard models adjusting for baseline characteristics, clinical profiles at presentation, and in-hospital treatments were used to assess the association of the number of SMuRFs with all-cause mortality at 30 days after STEMI presentation. Results A total of 1918 (11.8%), 11,503 (70.9%), and 2807 (17.3%) patients had 0, 1-2, and 3-4 SMuRFs at presentation, respectively. Patients with fewer SMuRFs were older and more likely to be females, experienced longer pre-hospital delays, and were less likely to receive primary percutaneous coronary intervention and evidence-based medications. Compared with those without any SMuRF, patients with 1-2 SMuRFs and 3-4 SMuRFs were associated with an HR of 0.74 (95% CI, 0.63-0.87) and 0.63 (0.51-0.77) for all-cause mortality up to 30 days in the unadjusted model (P-trend < 0.0001). However, after multivariate adjustment, the number of SMuRFs was positively associated with increased mortality risk (HR for 1-2 SMuRFs, 1.15 [0.95-1.39]; HR for 3-4 SMuRFs, 1.31 [1.02-1.68]; P-trend = 0.03), and the association was only significant among patients admitted to hospitals beyond 12 h from onset (HR for 1-2 SMuRFs, 1.39 [1.03-1.87]; HR for 3-4 SMuRFs, 2.06 [1.41-3.01]) but not their counterparts (P-interaction = 0.01). Conclusions The increased crude mortality risk among patients without SMuRFs is explained by confounding factors related to their poor risk profiles (old age, longer pre-hospital delays, and poor clinical management). After multivariate adjustment, a higher risk-factor burden was associated with poor prognosis among patients with STEMI.