Cold climate dual threats: lagged and nonlinear effects of air pollution and meteorological extremes on acute myocardial infarction risk

INTRODUCTION: Acute myocardial infarction (AMI) remains a major health concern in cold regions, where extreme meteorological conditions and air pollution can jointly elevate cardiovascular risk. However, the nonlinear and delayed impacts of diverse environmental stressors on different AMI subtypes remain insufficiently understood. METHODS: We conducted a retrospective time-series study including daily ST-elevation myocardial infarction (STEMI, ST refers to the ST segment on electrocardiograms) and non-ST-elevation myocardial infarction (NSTEMI) cases recorded in Heilongjiang Province, China from 2014-2023. Environmental exposures included key meteorological indicators (mean air temperature, surface temperature, snow depth, atmospheric pressure, sunshine duration, and ultraviolet intensity) and major air pollutants (PM[Formula: see text], PM[Formula: see text], NO[Formula: see text], SO[Formula: see text]). Extreme cold and heat were defined primarily using mean air temperature thresholds based on regional climatic characteristics (<-20[Formula: see text]C and >30[Formula: see text]C), while the full spectrum of non-extreme weather conditions was also assessed. Distributed Lag Nonlinear Models (DLNMs) were used to characterize nonlinear and lag-response relationships. RESULTS: STEMI risk significantly increased under stress, with acute effects observed at extremely low (<-20[Formula: see text]C) and high (>30[Formula: see text]C) mean air temperatures. NSTEMI showed a more gradual response, particularly to sustained heat exposure. Short-term PM[Formula: see text] exposure had a stronger effect on STEMI, whereas NO[Formula: see text] was more strongly associated with delayed NSTEMI risk. Atmospheric pressure between 990-1010 hPa elevated risk, while greater snow depth appeared inverse association. Non-linear patterns were also noted for sunshine duration and ultraviolet intensity. CONCLUSION: In cold-climate regions, both meteorological extremes and air pollution substantially affect AMI, but with distinct temporal and exposure-response characteristics between STEMI and NSTEMI. These findings highlight the need for subtype-specific environmental early warning systems and climate-adaptive cardiovascular prevention strategies.