ABSTRACT
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/m
@affil2:2) 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-years 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 Sp02 corr was significantly lower (p < 0.001) among smokers than nonsmokers (88.9 ± 3.3% vs.
94.7 ± 1.3%). In multiple regression 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). Conclusions: 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.
KEYWORD
Apnea-hypopnea index - carboxyhemoglobin - cigarette smoking - healthy subjects -
nocturnal oxygen saturation