Abstract Background and aims An increasing share of ST-segment elevation myocardial infarction (STEMI) occurs in patients without standard modifiable cardiovascular risk factors (SMuRFs). These SMuRF-less patients paradoxically experience worse outcomes, and the underlying drivers remain unclear. Environmental exposures such as air pollution, noise, temperature and residential green may contribute. We investigated, in a 9-year national Belgian cohort, whether SMuRF-less STEMI patients experience different environmental exposures and whether they are more susceptible to environmental triggers influencing STEMI onset and in-hospital mortality. Methods We analysed national health insurance data for all STEMI admissions in Belgium between 2012 and 2021 (excluding 2015). SMuRF-less patients had no hypertension, diabetes, smoking or dyslipidemia. Acute and chronic exposures to PM2.5, PM10, NO2, O3, temperature, noise and green space were estimated at residential address using high-resolution models. Socioeconomic data were individually linked. A time-stratified case-crossover design assessed associations between same-day air pollution and STEMI onset. Multivariable logistic regression examined chronic exposure - in-hospital mortality associations, adjusting for demographics, temporal and regional trends, socioeconomic and revascularisation status. Interaction analyses explored effect modification by SMuRF-less status in both associations between acute exposures and STEMI admission, and chronic exposures and in-hospital mortality. Results We identified 40,228 first-time STEMI admissions (mean age 66.6±14.1 years, 71% male). SMuRF-less cases accounted for 17.7%, decreasing by 0.44% per year (p=0.001). Compared to SMuRF-positive patients, SMuRF-less individuals were older (72.1±15.1 vs 65.4±13.7 years), more often female (36% vs 27%), less frequently revascularised (62% vs 79%), and had higher in-hospital mortality (25.9% vs 8.6%, all p0.001). In the month before STEMI, SMuRF-less patients had higher PM2.5 exposure (12.5±5.9 vs 12.1±5.5 µg/m³) and higher chronic roadway noise (56.6±7.2 vs 55.1±7.5 dB). SMuRF-less status independently conferred a 2.5-fold higher mortality risk (95% CI 2.3–2.7). Same-day IQR increases in PM2.5, PM10 and NO2 were associated with 2–4% more STEMI admissions (p0.05), with no modification by SMuRF-less status. Chronic monthly PM2.5 and NO2 exposures were associated with higher in-hospital mortality, but no environmental factor significantly interacted with SMuRF-less status. Conclusion In a national 9-year cohort, nearly one in five STEMI patients were SMuRF-less and had substantially higher in-hospital mortality. Although they experienced higher chronic PM2.5 and noise exposure, SMuRF-less patients did not exhibit increased susceptibility to acute or chronic environmental triggers. Further research should explore alternative biological or systemic mechanisms underlying the disproportionate worse outcomes in SmuRF-less STEMI.Example of daily STEMI cases & exposuresFor image description, please refer to the figure legend and surrounding text. Acute air pollution - STEMI associationsFor image description, please refer to the figure legend and surrounding text.
Potter et al. (Mon,) studied this question.