Associations Between Systemic Inflammation, Lung Function, and Respiratory Symptoms in Wildland Firefighters in Northern Thailand

Wildland firefighters are at risk of respiratory impairment and systemic inflammation. However, integrated assessments of inflammatory biomarkers, lung function, and symptoms are limited, especially among Thai firefighters. This study aimed to examine the associations between inflammatory biomarkers, lung function, respiratory symptoms, and related health factors in wildland firefighters in Northern Thailand. This cross-sectional study surveyed 146 wildland firefighters from eight Phayao stations using interviewer-administered questionnaires, including a Thai-adapted ATS-DLD-78-A questionnaire to assess demographics, lifestyle, health, work factors, and respiratory symptoms. High-sensitivity C-Reactive Protein (hs-CRP) levels, fractional exhaled nitric oxide (FeNO), and Pulmonary function (FVC%-predicted, FEV₁%-predicted, FEV₁/FVC%, FEF_25-75%-predicted) were measured. Data were analyzed using Mann-Whitney U, Kruskal-Wallis, and Spearman's correlation tests. Median hs-CRP was 1.44 µg/l, and median FeNO was 11.83 ppb. Significant positive associations were identified between hs-CRP levels and BMI (P=0.003) and FeNO (P<0.001). Lung function parameters (FVC%-predicted, FEV₁%-predicted, FEF_25-75%-predicted) were negatively correlated with hs-CRP levels (P<0.05). Elevated hs-CRP and reduced lung function were significantly associated with increased respiratory symptoms (P<0.05). Lifestyle factors, such as smoking and alcohol, were not significantly associated with hs-CRP. This study highlights associations between systemic inflammation, lung function decline, and respiratory symptoms in wildland firefighters, emphasizing the need for integrated biomarker and lung function monitoring for early detection in occupational health surveillance.