Smoking linked to sleep disturbances.

• Position: Nicotine Dependence

Cigarette smokers are four times as likely as nonsmokers to report feeling unrested after a night's sleep, according to research by the American College of Chest Physicians, Northbrook, Ill. The study reveals that smokers spend less time in deep sleep and more in light sleep than nonsmokers, with the greatest differences in sleep patterns seen in the early stages of slumber.

Researchers speculate that the stimulating effects of nicotine could cause smokers to experience withdrawal each night, which may contribute to these disturbances. "It is possible that smoking has time-dependent effects across the sleep period," explains study author Naresh M. Punjabi, Johns Hopkins University School of Medicine, Baltimore, Md. "Smokers commonly experience difficulty falling asleep due to the stimulating effects of nicotine. As night evolves, withdrawal from nicotine may further contribute to sleep disturbance."

Punjabi and his colleagues compared the sleep architecture of smokers with that of a matched group of nonsmokers, all of whom underwent home polysomnography. Previous studies comparing smokers and nonsmokers primarily have used subjective measures of sleep. Punjabi's study included smoking and nonsmoking subjects who were free of most medical comorbidities and medication use. "Finding smokers with no health conditions was challenging but, in order to isolate the effects of smoking on sleep...