Smoking and sleep disorders (population-based study under the WHO “MONICA-psychosocial” program)

Objective: to study the connection between smoking and sleep disorders in the open population of 45–64 year old in Novosibirsk. Patients and methods. IV screening of the population was carried out in 2003–2005, 1650 persons were examined (576 men, mean age – 54.23±0.2 years, response – 61%; 1074 women, mean age – 54.27±0.2 years, response – 72%). Attitudes towards smoking were studied using the scale “Knowledge and attitude to one's health” of the WHO “MONICA-psychosocial” program. To study sleep disorders and sleep duration, a standard Jenkins questionnaire was used. Results and discussion. In an open population of 45–64 years of age, 65.8% of men experienced sleep problems (satisfactory sleep – 53.6%, poor sleep – 12.2%) and 78.6% of women (satisfactory sleep – 58.9%, poor sleep – 19.7%; χ 2 =38.553; df=2; p<0.001). 78.9% of men and 34.7% of women smoked ( χ 2 =313.175; df=5; p<0.001). Men who smoke more often rated sleep as “bad” (82.9%) than “good” (76.2%; χ 2 =32.267; df=10; p<0.001). Women who tried to quit smoking were more likely to have “bad” sleep (4.7%) than “good” sleep (2.6%; χ 2 =69.747; df=10; p<0.001). Among male smokers, the duration of sleep was 5–6 hours (76.9%) more often than 9–10 hours (67.6%; χ 2 =3.696; df=2; p>0.05). Women who smoke were more likely to report 5–6 hours of sleep (30%) than 9–10 hours (18.2%). Conclusion. It has been established that smoking men and women aged 45–64 are more likely to experience both sleep disorders and lack of sleep.

Smoking can contribute to insufficient duration of sleep, since smokers need more time to fall asleep, and have a longer latent sleep delay [11]. Night smoking, a common cause of poor and insufficient sleep, occurs in approximately 41% of smokers [12]. Unhealthy sleep before and during smoking cessation is considered an independent cause of relapse, and insomnia is a clinically confirmed symptom of withdrawal [13].
Although it is well known that smokers are more vulnerable to unhealthy sleep, the alleged relationship between usual sleep and smoking has been less studied. Population studies are needed to measure a degree of insufficient sleep duration which can be a viable risk factor for continuing smoking. To date, studies of the relationship between the quality of sleep and smoking are limited. Understanding this relationship is crucial for the development of innovative clinical interventions and, as a result, improvement of the outcomes of smoking cessation [11].
Thus, the purpose of our study was to analyze the relationship between smoking and sleep disturbances among residents of Novosibirsk aged 45-64 years.  Smoking status was studied using the scale "Knowledge and Attitude to One's Health". To study sleep disturbances and duration of sleep, the standard Jenkins Sleep Questionnaire was used. The scales were adapted during a large-scale epidemiological study performed as part of the WHO program Monica (Multinational Monitoring of Trends and Determinants of Cardiovascular Disease) and subprograms of the Monica-Psychosocial Option Study (MOPSI). [16]. The questionnaires were filled by the participants on their own.
Statistical analysis was carried out using a package of computer programs SPSS 19 [15]. To check the statistical significance of the differences between the groups, the chi-squared criterion was used. The values p≤0.05 were considered statistically significant [17].
Significant differences in the duration of sleep between men and women in the open population of 45-64 years old have not been found (χ 2 =1.214, df=2, p>0.05) ( Table 2).
In the studied population, 50.1% of people smoked: men -78.9%, women -34.7%; Moreover, 12.2% of men and 3.6% of women tried to change their smoking behavior, but without success, and 10.6% of men and 3.4% of women tried to quit smoking for a while. 21.2% of men and 65.2% of women never smoked (χ 2 =313.175, df=5, p<0.001) ( Table 3).
Among men who have never smoked, good quality of sleep prevailed (23.9%); only 17.1% assessed their sleep as bad.

D i s c u s s i o n
Sleep is necessary to strengthen and maintain health, development and functioning at all stages of life. Insufficient amount and quality of sleep is associated with disorders of mental health, poor sociability, behavioral problems, development of obesity and its concomitant diseases, such as cardiovascular disease and diabetes [18]. In addition, sleep problems are associated with an increased frequency of depression, anxiety, worsening of attention, and aggressive behavior, [19]. Epidemiological studies show that about 26-35% of adults have poor sleep quality [19,20]. In our population, sleep problems turned out to be the most significant: two-thirds of men and women experienced some kind of sleep disturbances. It is well known that tobacco smoking is harmful to health in general and is one of the main causes of death and disease [19]. Although the association between smoking and sleep disorders is described in the world literature [21][22][23], there are some studies in which the authors did not find any connection between smoking and symptoms of insomnia or other sleep problems [21], which motivated us to study this topic. In our population sample (45 to 64 years old), two -thirds of men and one third of women were smokers. One fifth of men (20.1%) and two -thirds of women (65.2%) have never smoked, and among men who have never smoked, good sleep predominated. Most smoking men rated their sleep as "bad" (82.9%). Although among non-smoking women there was no significant difference in the self-assessment of sleep, those women who tried to quit smoking more often noted that they had bad sleep (4.7%). In the world literature there are studies in which sleep disturbances are regarded as a clinically confirmed symptom of nicotine withdrawal [24]. For example, at least 42% of people who abstain from smoking [25] (in some studies up to 80% of smokers [26]) usually experience sleep disturbances which are further aggravated after smoking cessation [27].

O R I G I N A L I N V E S T I G A T I O N S A N D M E T H O D S
As for the differences in the duration and time of sleep, smokers report a shorter sleep duration and more time needed to fall asleep than non-smokers [28]. Although we did not reveal significant differences in the duration of sleep in the studied population, a certain tendency to prevalence of 5-6-hour sleep (76.9%) was observed among smoking men. Smoking women more often had sleep duration of 5-6 hours (30%) than 9-10 hours (18.2%). Our data is consistent with the results found in the world literature. For example, population data obtained from the National Health and Nutrition Examination Survey (NHANES) showed that the average duration of sleep for smokers is 6.6 hours compared with 6.9 hours for non-smokers and those who never smoked [29]. According to The United Kingdom Biobank in a sample of 34401 smokers, 30.8% reported a short sleep (≤6 hours), and 9.3% reported a sleep duration of ≥9 hours [28]. In another study, it was shown that the duration of sleep was much shorter in adult smokers than in non-smokers, and this correlation was significant even for "light" smokers (<15 cigarettes per day) compared to nonsmokers [30].
Thus, the existing relationship between sleep and smoking can lead to understanding of how normalization of sleep can contribute to smoking cessation and, on the other hand, smoking cessation can improve the quality of sleep. Currently, sleep remains poorly understood and is insufficiently used to promote smoking cessation and prevent relapses in smokers who seek medical help to stop smoking. It is hoped that the totality of evidence that sheds light on the relationship between sleep, tobacco use and the results of smoking cessation will ultimately allow to identify a certain phenotype of sleep, which may increase the risk of continuing smoking. This base of knowledge, in turn, will serve as the basis for targeted approaches to interventions aimed at promoting smoking cessation in smokers who are most vulnerable to sleep deficit [28]. 3. Smoking men more often characterized their sleep as "bad" than "good" (82.9%). Non-smoking women did not have a significant difference in self-assessment of sleep. 4. Among smoking men, there was a tendency to a shorter sleep duration -5-6 hours (76.9%). Smoking women also more often reported the duration of sleep of 5-6 hours (30%).