BACKGROUND AND AIMS: Recent studies suggest that patients without standard modifiable cardiovascular risk factors (SMuRFs), hypertension, hypercholesterolemia, diabetes, or smoking, may experience higher short-term mortality after acute coronary syndrome (ACS) than those with risk factors. This study examined the relationship between SMuRF burden, ACS-free survival, and short-term outcomes, and explored potential mechanisms including index-event and dilution bias. METHODS: We analyzed data from 70,953 Caucasian patients with first-time ACS enrolled between 2005 and 2021 in the ISACS-TC Registry (NCT04008173). Patients with prior coronary heart disease were excluded. Traditional SMuRFs were identified from clinical history. The primary outcome was 30-day all-cause mortality; secondary measures included age at ACS onset and early death from hospital admission (≤1 day). Inverse probability weighting models adjusted for baseline imbalance. RESULTS: At least one SMuRF was present in 84 % of patients. Increasing SMuRF number was associated with progressively younger age at ACS (women: 67.1 vs 61.9 years; men: 62.8 vs 58.9 years; both P < 0.001). Conversely, 30-day mortality showed an inverse pattern, being highest in SMuRF-less patients and lowest among those with multiple SMuRFs (women: 16.3 % vs 7.7 %; men: 11.5 % vs 4.8 %). Diabetes alone conferred excess mortality (RR 1.29 [95 % CI 1.06-1.57] in women; 1.40 [1.16-1.69] in men), whereas isolated smoking, hypertension, or hypercholesterolemia were associated with lower risk. Early deaths at admission (≤1 day) were more frequent in SMuRF-less patients (36.8 % vs 31.7 %), suggesting arrhythmic mechanisms. CONCLUSIONS: SMuRFs remain strong determinants of earlier ACS onset and shorter ACS-free survival. The apparent paradox of higher mortality in SMuRF-less patients likely reflects index-event and dilution bias. Prevention strategies targeting smoking, hypercholesterolemia, and diabetes remain crucial to extend ACS-free life expectancy.