Kynurenine 3-Monooxygenase Protein and its Association on the Sleep Quality in Cigarette Smokers and Non-smokers

Objectives: Cigarette smoking significantly impacts sleep quality by altering neurochemical pathways. Nicotine, an agonist of nicotinic acetylcholine receptors, stimulates the release of dopamine, serotonin and norepinephrine, which can hinder the initiation and maintenance of sleep. This study focuses on the kynurenine pathway, where nicotine-induced Kynurenine 3-monooxygenase (KMO) activity leads to elevated levels of neurotoxic metabolites, such as quinolinic acid, that impair sleep quality in smokers. Methods: This cross-sectional study included 260 participants, equally divided into smokers and non-smokers, with informed consent obtained from all participants. Sleep quality was assessed using the Pittsburgh Sleep Quality Index (PSQI), covering parameters such as sleep latency, duration and disturbances. Saliva samples were collected and analyzed via ELISA to measure KMO biomarker levels. Statistical analyses, including Chi-Square and Mann-Whitney U tests, were employed to examine the relationship between KMO levels and sleep quality while acknowledging the limitations of self-reported data and potential confounders. Results: KMO levels were significantly higher in smokers (1.03±0.13) compared to non-smokers (0.95±0.09). Overall, 57.31% of participants reported good sleep, while 42.69% experienced poor sleep. Among smokers, 32.31% experienced poor sleep and only 17.69% had good sleep. Conversely, 39.62% of non-smokers reported good sleep, while 10.38% experienced poor sleep. Statistical analysis confirmed the association between smoking and disturbed sleep quality, though subgroup analyses by smoking intensity were not explored. Conclusion: The study confirms that smokers exhibit higher KMO levels and poorer sleep quality compared to non-smokers. These findings highlight the potential of targeting KMO levels as a therapeutic approach to mitigate sleep disturbances in smokers. Future research should explore pharmacological and behavioral interventions, while addressing broader public health implications and improving study methodologies.