Impact of Cold Spells on Community-Acquired Pneumonia Incidence

Background Climate change, characterized by extreme temperature fluctuations, has emerged as a significant risk factor for respiratory diseases, including pneumonia. Most previous studies have focused on hospital-acquired pneumonia or ICD-based data, which may have led to misclassification. This study aimed to evaluate the impact of extreme temperature events, particularly cold spells, on the incidence of community-acquired pneumonia in XXX, a coastal city in the Mediterranean region. Methods Meteorological data were obtained from the XXX Meteorology Station, and pneumonia cases diagnosed by pulmonologists were collected from six hospitals between January 2 and December 30, 2024. Generalized Additive Poisson Regression Models were applied to assess the lag effects (lag 0–3 days) of maximum and minimum temperatures on pneumonia incidence, adjusting for long-term trends and seasonality. Results A total of 13,651 pneumonia cases were recorded, of whom 51.5% (n = 7034) were male. Minimum temperature at lag 1 day was significantly associated with an increased risk of pneumonia (RR: 0.984, 95% CI: 0.973–0.996, p < 0.05), with the effect being more pronounced among the elderly (> 65 years). Conclusions Exposure to cold temperatures was associated with an increased incidence of pneumonia, particularly one day after exposure. These findings highlight the need for targeted public health interventions during cold spells, especially for vulnerable populations. Considering the longer incubation periods of pathogenic microbiomes, this association may be linked to the increased virulence of colonizing microorganisms triggered by cold weather conditions.