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Vaping, cigarette smoking worsen sleep quality in women
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Women who use electronic cigarettes in addition to conventional cigarettes experience more sleep disturbances than nonsmokers and those who only use one product, researchers reported in the American Journal of Respiratory and Critical Care Medicine.
“It is known that cigarette smoking disrupts sleep, through numerous mechanisms. We had noticed that users of e-cigarettes (vapers) tend to take puffs off these nicotine delivery devices immediately prior to bedtime (even keeping their e-cigarettes on their nightstand for quick access,” Laura E. Crotty Alexander, MD, associate professor of medicine in the division of pulmonary critical care and sleep at the University of California, San Diego (UCSD), and staff physician in the VA San Diego Healthcare System, wrote in an email to Healio Pulmonology. “This led to our hypothesis that inhaling nicotine immediately prior to bedtime would lead to similar sleep disruption as conventional smoking if nicotine was the primary driver of those effects.”
Worse sleep in women
In 274 study participants, Crotty Alexander and colleagues assessed sleep, cough and tobacco or e-cigarette use using the Pittsburgh Sleep Quality Index (PSQI), the Leicester Cough Questionnaire (LCQ) and the UCSD inhalant use questionnaire.
According to the data, PSQI scores were highest for participants who used e-cigarettes and conventional cigarettes (8.77) compared with those who used e-cigarettes only (6.87), those who smoked conventional cigarettes only (7.88) and nonsmokers (7.09; P = .027), with notable between-group differences among women but not men.
Additionally, among women, use of both products was linked to higher PSQI scores when compared with nonsmokers (P < .001), e-cigarette-only users (P = .001) and conventional cigarette-only users (P = .029). For men, however, PSQI scores appeared to be unaffected by dual use vs. no smoking, conventional cigarette-only use or e-cigarette-only use.
Also, among women only, users of both e-cigarettes and conventional cigarettes were more likely to have increased sleep latency than nonsmokers (P < .001) and e-cigarette-only users (P = .01). In both men and women, conventional cigarette use, as compared with no smoking, was linked to increased sleep latency.
When analyzing cough, the researchers noted that dual users had higher rates of chronic cough in the previous 30 days than nonsmokers, e-cigarette-only users or conventional cigarette-only users, and that dual use was associated with a more than twofold increase in the likelihood of experiencing chronic cough in the past 30 days (adjusted OR = 2.51; 95% CI, 1.21-5.19).
Dual use of e-cigarettes and conventional cigarettes was also associated with worse LCQ scores when compared with e-cigarette-only use (P = .017) and no smoking (P = .051). Worse sleep quality was also noted with the presence of cough, with a modest correlation between PSQI and LCQ scores in participants who reported cough.
Differences between women, men
Crotty Alexander noted that the researchers expected that the greatest effects on sleep would be observed in participants who used both cigarettes and e-cigarettes, “as dual users have been shown to take in higher quantities of nicotine than use of either product alone.”
The researchers did not expect, however, to see a difference between men and women.
“We were surprised that sleep quality in men was not affected by e-cigarette use, cigarette smoking or dual use of both. Along those same lines, we were surprised that sleep latency (the amount of time it takes to fall asleep) was so profoundly affected in women,” Crotty Alexander said.
Several factors may contribute to these differences, though.
“Women have greater nicotine withdrawal effects and less successful cessation attempts compared with men, which suggests that they have a greater susceptibility to nicotine via addiction and other pathways in the central nervous system (CNS). Also, gender plays a role in the prevalence of sleep disturbance in relation to insomnia, obstructive sleep apnea and chronic nocturnal cough,” Crotty Alexander said.
For instance, she noted, a recent large-scale study indicated that young women, as compared with men, are more vulnerable to sleep disturbances, independent of depression, socioeconomic status and lifestyle factors. Moreover, other studies have shown that women have an increased risk for insomnia, and chronic nocturnal cough secondary to gastroesophageal reflux disease (GERD), which may result in sleep fragmentation, is more severe in women.
“Nicotine has been identified as a known etiological factor for acid reflux due to its ability to cause lower esophageal sphincter dysfunction. Thus, we think that women are more susceptible to the effects of nicotine via increased insomnia (increased CNS activation) and increased nocturnal cough (due to greater incidence of GERD secondary to nicotine),” Crotty Alexander told Healio Pulmonology.
In terms of future research, there is much to explore, she added.
“We are actively working to expand our studies to better define the population at risk for the sleep-disturbing effects of inhaled nicotine. Also, we are examining mechanistically the effects of nicotine on nicotinic pathways and sleep centers in the brains of males and females, to better understand the gender differences at play,” Crotty Alexander said. – by Melissa Foster
For more information:
Laura E. Crotty Alexander, MD, can be reached at lcrotty@ucsd.edu; Twitter: @crottyalexander.
Disclosures: This study was supported by grants from the American Heart Association, the NIH, the American Thoracic Society, the VA of San Diego and the Tobacco-Related Disease Research Program. Crotty Alexander reports no relevant financial disclosures.