Smoking History and Nicotine Dependence Alter Sleep Features in Patients with Obstructive Sleep Apnea-Hypopnea Syndrome

<b>Introduction:</b> There are many aspects in the relationship between smoking and sleep that have not been investigated thoroughly yet, especially in regards to obstructive sleep apnea-hypopnea syndrome (OSAHS). <b>Methods:</b> In this cross-sectional study, 2359 participants, who have visited the sleep clinic of our hospital during a 13-year period and were former or current smokers, were included. Their smoking history, measured in packyears of smoking, and their nicotine dependence, measured with the Fagerström scale, were correlated with various epidemiological and sleep-related variables. <b>Results:</b> Patients with respiratory, cardiovascular and metabolic comorbidities were older, more obese and presented a significantly greater history in packyears of smoking. Packyears were positively correlated with the Epworth sleepiness scale (ESS) (r = 0.06, <i>p</i> = 0.007), with %REM sleep time (r = 0.19, <i>p</i> = 0.042), apnea-hypopnea index (AHI) (r = 0.10, <i>p</i> < 0.001), oxygen desaturation index (ODI) (r = 0.10, <i>p</i> < 0.001), mean and maximum apnea duration (r = 0.10, <i>p</i> < 0.001 and r = 0.11, <i>p</i> < 0.001, respectively), while they were negatively correlated with mean and minimum SaO₂ (r = -0.18, <i>p</i> < 0.001 and r = -0.13, <i>p</i> < 0.001, respectively). Furthermore, smoking history exhibited a significantly increasing trend with increasing OSA diagnosis and severity (<i>p</i> < 0.001). Patients with abnormal movements during sleep and those with restless sleep showed a significantly higher nicotine dependence, measured with the Fagerström scale, compared to those without abnormal movements or restless sleep (5.4 ± 2.8 vs. 4.7 ± 2.8, <i>p</i> = 0.002 and 5.1 ± 2.9 vs. 4.7 ± 2.7, <i>p</i> = 0.043). <b>Conclusions:</b> Smoking history in packyears probably affects OSAHS characteristics, while nicotine dependence seems to be related more with abnormal sleep behaviors.