Seasonal Variations in the Pathogenesis of Acute Coronary Syndromes

BACKGROUND: Seasonal variations in acute coronary syndromes (ACS) have been reported, with incidence and mortality peaking in the winter. However, the underlying pathophysiology for these variations remain speculative. METHODS AND RESULTS: Patients with ACS who underwent optical coherence tomography were recruited from 6 countries. The prevalence of the 3 most common pathologies (plaque rupture, plaque erosion, and calcified plaque) were compared between the 4 seasons. In 1113 patients with ACS (885 male; mean age, 65.8±11.6 years), the rates of plaque rupture, plaque erosion, and calcified plaque were 50%, 39%, and 11% in spring; 44%, 43%, and 13% in summer; 49%, 39%, and 12% in autumn; and 57%, 30%, and 13% in winter (P=0.039). After adjusting for age, sex, and other coronary risk factors, winter was significantly associated with increased risk of plaque rupture (odds ratio [OR], 1.652; 95% CI, 1.157–2.359; P=0.006) and decreased risk of plaque erosion (OR, 0.623; 95% CI, 0.429–0.905; P=0.013), compared with summer as a reference. Among patients with rupture, the prevalence of hypertension was significantly higher in winter (P=0.010), whereas no significant difference was observed in the other 2 groups. CONCLUSIONS: Seasonal variations in the incidence of ACS reflect differences in the underlying pathobiology. The proportion of plaque rupture is highest in winter, whereas that of plaque erosion is highest in summer. A different approach may be needed for the prevention and treatment of ACS depending on the season of its occurrence. REGISTRATION: URL: https://www.clini​caltr​ials.gov. Unique identifier: NCT03479723.