Cigarette smoking behavior and respiratory alterations during sleep in a healthy population

Background and study objective: The importance of tobacco smoking in the origin of sleep ventilatory abnormalities is disputed. The purpose of our study was to evaluate the influence of cigarette smoking behavior on the sleep respiratory alterations in a healthy population. Design and methods: We studied 38 healthy volunteers (21 M, 17 F; age 42 ± 12 years; BMI 23.7 ± 3.6 kg/m2) who were divided into two matched groups: current tobacco smokers (n = 18; over 10 pack-years) and nonsmokers (n = 20). All individuals underwent a single nocturnal domiciliary polygraphic study (Polygraphics CNS, Minneapolis, Minnesota). Apnea (AI), apnea-hypopnea (AHI), and desaturation (DI) indexes were defined according to conventional criteria. A nocturnal hypoxia index (NHI) was calculated as an index of the magnitude and duration of oxyhemoglobin desaturation during sleep. The mean transcutaneous oxygen saturation (SpO2) of the first 60 seconds of oxymetric registration (subject supine and awake) was considered basal SpO2. Venous carboxyhemoglobin (COHb) levels were measured (CO- Oximeter AVL-912, Basel, Switzerland) in all individuals before (22:00 h) and after (10:00 h) sleep. A correction factor of 0.9 x COHb was applied to the basal SpO2 values to calculate the corrected basal SpO2 (SpO2 corr). Results: AI, AHI, and DI were not significantly different between smokers and nonsmokers. The smokers have significantly higher NHI than nonsmokers [median (25th percentile-75th percentile): 5.3 (0-39.7) vs. 0.5 (0-1.7); p=0.017]. There were significant correlations (P<0.05) in smokers between NHI and pack-year index, between NHI and COHb levels, and between current smoking intensity and COHb levels. As expected, smokers had higher COHb levels at 10:00 as well as at 22:00 hours. The SPO2 corr was significantly lower (p<0.001) among smokers than nonsmokers (88.9 ± 3.3% vs. 94.7 ± 1.3%). In multiple regresion analyses, AHI and DI showed a significant correlation (p=0.02 and p=0.05, respectively) with habitual snoring, and NHI with pack-years and BMI (p=0.02 and p=0.04, respectively). Conclussion: Cigarette smoking does not seem to be associated with increased apneic activity during sleep. However, it is associated with a decrease in nocturnal oxygen saturation.