Seasonal variation and first-time acute myocardial infarction in a public tertiary hospital

BACKGROUND: Cardiovascular diseases are the leading cause of death worldwide, with acute myocardial infarction (AMI) accounting for a large proportion of mortality. Seasonal variation has been proposed as a short-term trigger of AMI, yet findings remain inconsistent, particularly in low- and middle-income countries. This study aimed to evaluate the association between seasonality and first-time AMI hospitalizations in a hospital-based adult population. METHODS AND MATERIALS: This was a hospital-based analytic cross-sectional study using retrospective clinical records from a public tertiary referral hospital (March 2023–March 2025). Adults aged ≥18 years hospitalized in Internal Medicine, Cardiology, or the Coronary Care Unit were included. First-time AMI admissions were identified, excluding prior AMI or incomplete records. Seasonality was categorized as warm (March 21–September 22) and cold (September 23–March 20). Demographic and clinical data were obtained from medical records. Frequencies and percentages were calculated. Poisson regression models with a log link and an offset for total admissions estimated prevalence ratios (PRs) and 95% confidence intervals (CIs). RESULTS: Among 5126 admissions, 334 (6.5%) were first-time AMI. A greater proportion occurred during the cold season (54.5% vs. 45.5%). The cold season was associated with higher AMI prevalence (adjusted PR = 1.25; 95% CI: 1.02–1.54), particularly among adults ≥65 years and smokers. CONCLUSION: First-time AMI hospitalizations were more frequent during the cold season. These findings highlight seasonality as a clinically relevant contextual factor that may help anticipate periods of increased cardiovascular burden and inform preventive and resource-planning strategies in hospital settings. However, findings should be interpreted within this specific healthcare and socioeconomic context.