Smoking Disturbs the Beneficial Effects of Continuous Positive Airway Pressure Therapy on Leptin Level in Obstructive Sleep Apnea

Background: This study aimed to determine how smoking alters the effect of positive airway pressure (PAP) therapy on metabolic syndrome in obstructive sleep apnea (OSA). Methods: In this clinical trial, morphometric measures, metabolic syndrome parameters, and apnea-hypopnea index (AHI) in OSA patients were recorded and compared between active smokers and non-smokers. The mean change in metabolic syndrome parameters measured before and after 3 months of PAP therapy was determined. The study included 72 males and 43 females. Results: Morphometric values and mean AHI did not differ between active smokers and non-smokers. When the percentage of unchanged, increased, or decreased metabolic parameters measured before and after treatment was analyzed, leptin level tended to increase in active smokers with OSA after PAP therapy compared with nonsmokers (P=0.034, adjusted for confounders). Conclusion: Serum leptin level was stable or decreased in non-smokers, while 40% of active smokers had increased leptin level. Therefore, smoking plays a predisposing role in leptin resistance despite PAP therapy in OSA patients.