A strong association between smoking and OSA has been demonstrated in observational studies. In one small cross-sectional study, investigators found a smoking prevalence of 35% in patients with OSA (apnea-hypopnea index [AHI] > 10) compared with only 18% in an unmatched group of patients without OSA (AHI < 5) (P < .01).21 Kim et al22 examined 28 male smokers and 29 male nonsmokers without COPD who underwent uvulopalatopharyngoplasty for OSA. The smokers had a higher mean AHI than did the nonsmokers (mean ± SD, 30 ± 15 vs 22 ± 11; P = .03). In a study of 301 randomly chosen Israeli driver’s license applicants, smoking several times daily was found to be the third most important predictor for sleep-disordered breathing, after age and sleepiness (Epworth Sleepiness Scale), but before BMI.23 The University of Wisconsin Sleep Cohort Study, one of the largest cohort studies to investigate OSA in the United States, reported the results of overnight polysomnography of, and health interviews with, 811 participants. Current smokers had a greater odds of moderate or severe OSA compared with nonsmokers (OR, 4.4; 95% CI, 1.5-13).24 This result persisted after adjustment for sex, age, BMI, education, daily amount of caffeinated beverages consumed, and weekly number of alcoholic beverages consumed. Persons smoking at least two packs of cigarettes each day had the greatest risks of mild OSA (OR, 6.7; 95% CI, 1.2-38) and moderate or severe OSA (OR, 40; 95% CI, 1.4-50). Former smoking, however, was not related to OSA (OR, 1.3; 95% CI, 0.8-2.3), suggesting that the predominant effect of smoking on OSA risk may be short term or the sample size of this large epidemiologic study was not sufficient to detect a difference. It appears from these studies that, even in the absence of COPD, there is a relationship between smoking and OSA.