Forced vital capacity of healthy Iranian adults in Tehran

The global prevalence of chronic respiratory diseases is increasing, necessitating accurate lung function assessment. Forced Vital Capacity (FVC) is an important spirometric indicator of respiratory health. This study aims to determine the normal FVC values in healthy Iranian adults in Tehran, considering variables such as age, sex, environmental exposure, education, occupation, and comorbidities. A cross-sectional study was conducted on 732 healthy participants aged ≥ 40 years from 22 districts of Tehran. Spirometry was performed via a calibrated spirometer, and demographic data were collected via standardized questionnaires. Exclusion criteria included smoking, recent surgery, respiratory symptoms, and a history of lung disease. Data analysis was performed via SPSS, with p-values < 0.05 considered significant. The mean FVC was 3.3 ± 0.86 L in men and 2.4 ± 0.62 L in women (p < 0.001). FVC declined with age and showed a positive correlation with height (p < 0.001) and a negative correlation with body mass index (BMI, p = 0.012). Significant variations in FVC were observed across different districts, with the highest values in District 2 (3.09 ± 0.82 L) and the lowest in District 16 (2.32 ± 0.57 L). FVC was lower in individuals with comorbidities such as heart disease, hypertension, and diabetes. It was also reduced in unemployed men and increased with higher educational attainment. This study provides baseline FVC values for healthy Iranian adults, highlighting the influence of demographic and environmental factors. Region-specific values are vital for accurate respiratory disease assessment and management.