Correlation between Upper Airway and Lower Airway Function in Current Smokers, Never Smokers and Former Smokers
Authors: Ravi Rojan , Pal Indranil , Kumar Saumitra , Babu Anindita Sinha , Halder Indranil , Roy Suman 
Published: July 2023

Introduction: Smoking is the major risk factor for the development of chronic lung disease and airway malignancy. The development of biomarkers for disease onset and early progression is hindered by the accessibility of the primary tissue in the lungs, so there is a need to evaluate alternative sites for surrogate biomarkers. The harmful effects seen in the lower and distal airways are also mirrored in the nasal epithelium as one airway and one disease.

Objective: To study the correlation between nasal mucosal cytology, mucociliary function, nasal airflow and lung function among the current smokers, never smokers, and former smokers.

Methods: Cross sectional, observational study from a tertiary care hospital.105 subjects were randomly distributed on the basis of smoking pattern into 3 groups, never smoker, current smoker and former smoker. Nasal mucosal cytology and function were assessed by saccharin transit time test (STT), peak nasal inspiratory flow(PNIF) and nasal ciliated cells & goblet cell ratio. The lower airway was assessed by spirometry.

Results: The increase in saccharin transit time was statistically significant (p <.001) in current smokers and former smokers compared to never smokers. The lower mean goblet cell count of the former smoker group was statistically significant when compared to the never smoker and current smoker groups, (p.023) while the change in ciliated cell/ goblet cell ratio remained statistically insignificant. The decrease in FEV1/FVC is statistically significant (p 0.036) in former smokers compared to both never smokers and current smokers.

Conclusion: Nasal mucociliary function is reduced in smokers and this reduction is permanent as cessation of smoking does not improve the mucociliary function.

Lay Summary: The study is focused to find out whether harmful effects seen in the lower and distal airways are also mirrored in the nasal epithelium as one airway and one disease in current smokers, never smokers and former smokers and thus to find out an early predictor of chronic lung disease so that intervention may be initiated to counsel and help the smokers taking part in the study to quit smoking. It was a Cross sectional, observational study from a tertiary care hospital.105 subjects were randomly distributed on the basis of smoking pattern into 3 groups, never smoker, current smoker and former smoker. Nasal mucosal cytology and function were assessed by saccharin transit time test (STT), peak nasal inspiratory flow (PNIF) and nasal ciliated cells & goblet cell ratio (CC/GC). Lower airway was assessed by spirometry.The increase in saccharin transit time is statistically significant (p <.001) in current smoker and former smoker compared to never smoker which implied that nasal mucociliary function is reduced in smokers. The lower mean goblet cell count of the former smoker group was statistically significant when compared to the never smoker and current smoker groups. (p.023) while the changes in ciliated cell and goblet cell ratio remained statistically insignificant. The decrease in FEV1/FVC is statistically significant (p 0.036) in former smokers compared to both never smokers and current smoker which lead us to the conclusion that  this reduction is permanent and cessation of smoking does not improve the mucociliary function.