Abstract Background Seasonal variation in the incidence and presentation of acute coronary syndrome (ACS) has been reported worldwide, with higher rates typically observed during colder months. Climatic factors such as temperature, humidity, and atmospheric pressure may influence cardiovascular stress, plaque instability, and thrombosis. However, available evidence remains inconsistent across regions and climates. Assessing these seasonal patterns may help elucidate geographic disparities and guide preventive strategies. Purpose To compare the clinical characteristics and outcomes of patients admitted with ACS during warm versus cold seasons, and to assess potential seasonal differences in in-hospital course. Methods A single-centre study of 1455 patients with ACS between October 2010 and June 2025, included in a voluntary, observational, prospective registry. Patients were divided according to time of event into warm (spring–summer) versus cold (autumn–winter) season. Baseline characteristics and in-hospital complications were analysed. Results A total of 1455 patients were included, with a mean age of 64.0 ± 12.8 years (range 29–96), and the majority were male (72.9%). The study cohort was composed of 518 patients in the warm season group (35.6%) and 937 patients in the cold season group. Baseline characteristics including age (67.03 vs. 66.98 years, p = 0.093), body mass index and cardiovascular risk factors were similar between groups. The warm season group had more previous chronic renal disease (5.0% vs. 3.0%, p = 0.048) as well as higher creatinine at admission (1.14 vs. 1.03 mg/dL, p = 0.029). In terms of ACS type, almost half of patients in both groups presented with ST-Elevation Myocardial Infarction (STEMI), with no differences in Killip class (p = 0.321) or left ventricular ejection fraction at discharge (median LVEF: 51 14–73 vs. 50 18–75, p = 0.461). Heart failure therapy at discharge was also comparable between groups. No differences were observed in in-hospital mortality, heart failure, or rhythm complications. A composite outcome including in-hospital mortality, cardiogenic shock, and reinfarction was created, showing no significant difference between warm and cold season groups (p = 0.4). Conclusions Although baseline characteristics and ACS type were largely similar across seasons, the higher prevalence of chronic renal disease in the warm season group warrants further investigation. Seasonal patterns did not significantly affect in-hospital mortality or major complications.
Fernandes et al. (Fri,) studied this question.