The study also reveals that smokers spend less time in deep sleep and more time in light sleep than non-smokers, with the greatest differences in sleep patterns seen in the early stages of sleep.

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Researchers speculate that the stimulating effects of nicotine could cause smokers to experience nicotine withdrawal each night, which may contribute to disturbances in sleep.

“It is possible that smoking has time-dependent effects across the sleep period,” said study author Dr Naresh M. Punjabi from Johns Hopkins University School of Medicine. “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.”

Smokers compared to non-smokers
Unlike most studies on sleep comparing smokers and non-smokers, Punjabi’s study included smoking and non-smoking subjects who were free of most medical co-morbidities and medication use.

“Finding smokers with no health conditions was challenging. But in order to isolate the effects of smoking on sleep architecture, we needed to remove all factors that could potentially affect sleep, in particular, coexisting medical conditions,” said Punjabi.

“In the absence of several medical conditions, sleep abnormalities in smokers could then be directly associated with cigarette use.”

An additional strength of this study was that sleep architecture was analysed using both the conventional method of visual classification of electroencephalogram (EEG) patterns and through power spectral analysis of the EEG, which relies on a mathematical analysis of different frequencies contained within the sleep EEG.

Previous sleep studies have relied on visual scoring of sleep stages, which is time-consuming and subject to misclassification,” said Punjabi. “Spectral analysis allows us to more objectively classify the sleep EEG signals and helps detect subtle changes that may have been overlooked with visual scoring.”

Visual scoring of sleep staging showed similar results between smokers and non-smokers.

Smokers has less deep sleep
However, spectral analysis showed that smokers had a lower percentage of delta power, or deep sleep, and a higher percentage of alpha power, or light sleep.

When asked about sleep quality, 22.5 percent of smokers reported lack of restful sleep compared with 5 percent of non-smokers. Spectral analysis also showed that the largest difference in sleep architecture occurred at the onset of sleep, which supports the premise that nicotine’s effects are strongest in the early stages of sleep and potentially decrease throughout the sleep cycle.

The researchers speculate the results of their study may have significant future implications in the area of smoking cessation.

“Many smokers have difficulty with smoking cessation partly because of the sleep disturbances as a result of nicotine withdrawal,” said Punjabi. “By understanding the temporal effects of nicotine on sleep, we may be able to better tailor nicotine replacement to minimise the withdrawal effects that smokers experience, particularly during sleep.” – (EurekAlert!) Source: CHEST

Read more:
Smoking Centre
Sleep Centre

February 2008
 

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