Effects of Smoking on the Sleep-Wakefulness Cycle: Actigraphic Research Among University Students

Sleep is one of the most important biological processes of human beings, and its functions are essential to cognitive and emotional as well as mental and physical health. Nicotine, a chemical stimulant in cigarettes and e-cigarettes, acts both as a stimulant and a relaxant on the human central nervous system. Cigarette and e-cigarette smoking may not only delay sleep onset and reduce total sleep time but also alter the normal sleep stage architecture. In addition to lower academic performance, inadequate sleep quality and disrupted circadian rhythms are also known to cause various other poor health outcomes in both physical and mental health, including increases in chronic disease, especially in university students. This study aimed to assess the effect of cigarette and e-cigarette smoking on the sleep-wakefulness cycle in students of the University of Georgia, Tbilisi, objectively, using wearable actigraphy. Questionnaires were collected to assess the same effects subjectively.

This study design was a cross-sectional observational design of 18-25-year-old university students categorized into current cigarette/e-cigarette users (smokers) and current non-smokers who reported at least one year without smoking/vaping. The data for the sleep-wakefulness parameters were collected using wrist-worn wearable devices manufactured by Huawei Technologies Co., Ltd. and Zepp Health Corporation and measured for seven continuous days of the total sleep duration, rapid eye movement sleep duration (REM-SD), deep sleep duration, and number of nocturnal awakenings. A questionnaire was distributed via Google Forms to university students to assess their sleep patterns and associated behaviors. Sleep-wakefulness data were then statistically analyzed using IBM SPSS Statistics version 23.0. An independent-samples t-test was used to compare parameters between smokers and non-smokers; p <0.05 was considered statistically significant.

A total of 47 smokers and 50 non-smokers had successfully collected their sleep-wakefulness data using an actigraphy device. A total of 107 responses from the surveys were collected, with 96 smokers and 11 non-smokers. The sleep parameters results showed that total sleep time was significantly shorter in smokers compared to non-smokers (381.60±163.22 minutes vs. 410.37±133.71 minutes, p = 0.012), whereas REM-SD was also significantly reduced in smokers compared to non-smokers (55.09± 57.55 minutes vs. 63.89±39.94 minutes, p = 0.020). There was no significant difference in deep sleep duration between smokers and non-smokers (81.10 vs. 60.79 minutes vs. 88.78 vs. 45.89 minutes, p = 0.061). The survey data showed that many smokers had smoked a cigarette close to bedtime, slept lighter, took a longer time to sleep, woke up frequently during the night, and felt fatigued during the morning.

Our study results found that cigarette and e-cigarette smoking may cause poorer sleep quality by altering two of the main sleep parameters. Nicotine usage leads to significant reductions in sleep quality parameters, including total sleep time and REM-SD, and thus it may also adversely affect other physiological benefits, including improved mental health and physical health. Therefore, programs focused on health education may target smokers who are involved in these poor sleep characteristics as one of the interventions to help them with cessation and to improve their overall well-being.