Evaluation of Pulmonary Function Changes in Smokers versus Non-Smokers Using Spirometry

Background: Cigarette smoking is a major preventable cause of morbidity and mortality worldwide, contributing significantly to chronic respiratory diseases. Pulmonary function testing using spirometry provides an objective means of assessing smoking-related airway impairment and detecting early subclinical changes. Objective: This study aimed to evaluate pulmonary function changes among smokers compared to non-smokers using spirometry in a tertiary care setting in Punjab, Pakistan. Methods: A Cross-sectional comparison study was conducted at two tertiary care facilities between March 2024 and March 2025. Using purposive sampling, 90 individuals between the ages of 20 and 60 were enrolled, 45 of them were smokers and the remaining 45 were non-smokers. Using a systematic questionnaire, demographic and clinical data, including smoking history, were collected. The American Thoracic Society (ATS) recommendations were followed while doing the spirometry, and the findings were assessed for peak expiratory flow rate (PEFR), forced expiratory volume in one second (FEV1), forced vital capacity (FVC), and FEV1/FVC ratio. The Statistical Package for Social Sciences (SPSS) software version 26 was used to analyze the data. Pearson's correlation test was used to determine the relationship between smoking exposure and spirometric indices, and independent t tests were used for group comparisons. Results: Smokers demonstrated significantly reduced mean FEV1 (2.29 ± 0.61 L vs. 3.01 ± 0.55 L, p < 0.001), lower FEV1/FVC ratios (68.5% ± 7.2 vs. 81.1% ± 6.5, p < 0.001), and decreased PEFR (314.6 ± 72.8 L/min vs. 386.2 ± 68.9 L/min, p < 0.001) compared to non-smokers. Obstructive patterns were observed in 42.2% of smokers versus 8.9% of non-smokers. Pack-year analysis showed a significant inverse correlation with both FEV1 (r = –0.41, p = 0.004) and FEV1/FVC ratio (r = –0.38, p = 0.006). Conclusion: Smoking is strongly associated with impaired pulmonary function, particularly obstructive airway changes. Spirometry is a valuable tool for early detection, highlighting the need for routine screening and targeted smoking cessation interventions to prevent progressive lung disease.