INTRODUCTION Obstructive sleep apnea (OSA) is a serious sleep disorder characterized by repetitive episodes of paused or shallow breathing during sleep. Patients with OSA often have excessive daytime sleepiness. The role of cigarette smoking in OSA remains controversial. The aim of this study was to examine the relationship between cigarette smoking and OSA. METHODS In this retrospective chart review, we reviewed 18-month sleep laboratory charts in central Taiwan. We collected data regarding sleep, current cigarette smoking status, sex, age, body mass index (BMI), neck circumference, Epworth Sleepiness Scale score, and polysomnographic sleep parameters. In total, 733 subjects were recruited; among these, 151 were smokers and 582 were nonsmokers. RESULTS Smokers had significantly higher apnea--hypopnea index (p<0.001) for non-rapid eye movement sleep stage, higher apnea--hypopnea index (p<0.001) for total sleep time, and higher snore frequency (p<0.001) in t-test analysis. They also demonstrated higher Epworth Sleepiness Scale scores, shorter sleep times, lower percentage of slow-wave (deep) sleep, and longer snore times. However, no significant association was found between cigarette smoking and OSA after adjusting for sex, age, and BMI (OR=1.02, 95% CI: 0.66--1.57). CONCLUSIONS We did not find any significant association between cigarette smoking and OSA after adjusting for age, sex, and BMI. Further well-designed prospective controlled cohort studies might clarify the relationship between cigarette smoking and OSA. [ABSTRACT FROM AUTHOR]