Spirometric Lung Function Among Smokers and Non-Smokers: A Cross-Sectional Study in University Students

Background: With the increasing use of cigarettes and electronic nicotine delivery systems (ENDS) in young adults, growing concern exists regarding lung health among university students. While the adverse respiratory effects of smoking are well established in older populations, early functional changes among young adults remain less well studied. Identifying such changes in this vulnerable population is crucial due to the risk of detrimental long-term health effects and the role of implementing early preventive measures. This study aims to compare the effects of nicotine use, sex, and body mass index (BMI) on the spirometric lung function parameters, including FEV1, FVC, and FEV1/FVC ratio, of smokers (including cigarette, ENDS, shisha, and midwakh users) and non-smokers in a university population. Methods: This cross-sectional study was conducted at Ajman University, United Arab Emirates. A convenience sample of 652 smokers and non-smokers students was initially recruited voluntarily, of whom 630 participants met the spirometry acceptability criteria and were included in the final analysis. Lung function was assessed using spirometry performed according to the guidelines of the American Thoracic Society and European Respiratory Society. Forced expiratory volume in one second (FEV1), forced vital capacity (FVC), and the FEV1/FVC ratio were recorded and expressed as percentages of predicted values based on Global Lung Function Initiative reference equations. Lung function parameters were compared according to smoking status, sex, and BMI. Results: A total of 630 students were included (60.5% males; the majority aged 20–22 years). The prevalence of smoking was 28.9% and was significantly higher among males than females (38.6% vs. 14.1%; OR = 3.86, p < 0.001). Smokers demonstrated a significantly lower FEV1/FVC ratio compared with non-smokers (0.84 ± 0.07 vs. 0.86 ± 0.07, p < 0.001), despite slightly higher predicted FEV1 and FVC values. Males exhibited higher predicted lung volumes than females, whereas females had higher FEV1/FVC ratios (p < 0.001). Lung function varied significantly across BMI categories (p < 0.001), with increasing BMI associated with higher predicted lung volumes but lower FEV1/FVC ratios. Stratified analysis showed that male smokers had the lowest FEV1/FVC ratios, while female non-smokers had the highest. Conclusions: Smoking, sex, and BMI significantly influenced lung function in this cohort. Smokers demonstrated reduced FEV1/FVC ratios, indicating early airflow limitation. Males were more likely to smoke and had higher lung volumes, while females showed higher FEV1/FVC ratios. Increasing BMI was associated with higher lung volumes but lower FEV1/FVC ratios. These findings suggest that early pulmonary changes may occur in young adults, highlighting the importance of early screening, careful interpretation of spirometry, and the implementation of targeted public health interventions to reduce nicotine use, promote smoking cessation, and support lung health among university students.