Climatic determinants of antibiotic use in Southern Thailand: Retrospective longitudinal study during 2021 to 2023

Background: Antibiotic consumption is influenced by multiple factors, including environmental conditions. In tropical regions, climate variability may contribute to seasonal patterns of infectious diseases and prescribing behaviors. This study examined the association between climatic variables and antibiotic use in a tertiary hospital in southern Thailand. Methods: We analyzed 7,696 prescriptions of tetracyclines (n = 971), beta-lactams and penicillins (n = 4,208), and macrolides (n = 2,517) dispensed from 2021 to 2023. Defined daily doses (DDDs) were modeled using generalized additive models and distributed lag nonlinear models to assess associations with temperature, humidity, and rainfall, incorporating delayed and nonlinear effects. Results: Tetracycline use peaked in January with over 120 DDDs/biweek and declined sharply thereafter. Distributed lag nonlinear models revealed a 45-60% increase in tetracycline use following temperature drops of ≥2 °C after 3-4 biweeks. Beta-lactam use rose by 20-30% in response to rising temperatures within 1-2 biweeks. Macrolide prescribing decreased by up to 25% in periods of high humidity (>80%) and increased with sudden temperature fluctuations. Increased rainfall (>100 mm/biweek) was significantly associated with higher beta-lactam DDDs. Conclusion: Climatic factors influence antibiotic consumption patterns in class-specific ways. Incorporating environmental surveillance into antimicrobial stewardship programs may improve preparedness and resource allocation. Further multicenter studies are needed to confirm these findings and assess pathogen-specific implications.