A new study by researchers in the US has found that cigarette smokers don’t sleep as well as non smokers: they are four times more likely to report feeling unrested after a night’s sleep than non smokers.
The study is published in the February printed issue of the journal Chest and is the work of Dr Naresh M Punjabi, who is Associate Professor of Medicine and Epidemiology based at the Johns Hopkins University School of Medicine in Baltimore, Maryland, and colleagues.
The researchers also found that smokers spent more time in light sleep and less time in deep sleep compared to non smokers. The biggest differences occurred in the early stages of sleep, they said.
Speculating on their findings, the researchers suggested nicotine withdrawal as the most likely cause.
“It is possible that smoking has time-dependent effects across the sleep period,” said Punjabi.
“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”, he added.
Punjabi and colleagues compared the electroencephalogram (EEG) sleep patterns of 40 smokers with those of a matched group of 40 non smokers. None of the participants had any potentially confounding health or medication issues that could have interfered with the findings, said the researchers.
As Punjabie explained:
“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.”
“In the absence of several medical conditions, sleep abnormalities in smokers could then be directly associated with cigarette use,” he added.
The analysis was considered more robust than many studies that rely on EEGs, because the researchers used spectral analysis and not just visual methods of classifying the EEG patterns. Spectral analysis uses mathemeatics to analyse the different frequencies in the EEG sleep patterns.
“Previous sleep studies have relied on visual scoring of sleep stages, which is time-consuming and subject to misclassification”, explained 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,” he added.
Visual scoring of the EEG sleep stage patterns showed little difference between the smokers and non smokers.
But when they analysed the patterns using spectral analysis, the smokers had a lower percentage of “delta power” which equates to less deep sleep, and a higher percentage of “alpha power” which equates to more light sleep, compared to the non smokers.
The researchers also asked the participants about their sleep quality.
22.5 per cent of smokers reported lack of restful sleep. This compared to 5.0 per cent only of non smokers.
Spectral analysis showed that the biggest differences in the sleep patterns of smokers versus non smokers happened at the beginning of sleep. This was in keeping with the idea that nicotine exerts its strongest effect in the early stages of sleep and then lessens as sleep progresses.
The researchers suggested that their findings could help design programmes to help smokers quit.
“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 minimize the withdrawal effects that smokers experience, particularly during sleep,” he added.
Surprisingly, although smokers reported more caffeine consumption than non smokers, this was not found to have an effect on either the EEG patterns or reported sleep quality.
Commenting on the findings, Dr Alvin V Thomas, Jr, President of the American College of Chest Physicians, said:
“The long-term effects of smoking on respiratory and cardiovascular health are well-known.”
“However, this study is significant because it suggests that smokers may also be deprived of the much-needed restorative effects of sleep. This study provides yet one more reason to stop smoking or to never start”, said Thomas.
“Power Spectral Analysis of Electroencephalographic Activity during Sleep in Cigarette Smokers.”
Lin Zhang, Jonathan Samet, Brian Caffo, Isaac Bankman, and Naresh M. Punjabi.
Chest, Prepublished online October 9, 2007.
DOI:10.1378/chest.07-1190
Source: American College of Chest Physicians news release.
Written by: Catharine Paddock, PhD