|Year : 2021 | Volume
| Issue : 2 | Page : 197-204
Stress, sleep, and use of sleep aids among physicians during the COVID-19 pandemic
Deemah AlAteeq1, Aljoharah Almokitib2, Maya Mohideen2, Nouf AlBlowi2, Amel Fayed2, Sultan M Alshahrani3
1 Department of Clinical Sciences, College of Medicine; Department of Neurosciences, King Abdullah Bin Abdulaziz University Hospital, Princess Nourah Bint Abdulrahman University, Riyadh, Saudi Arabia
2 Department of Clinical Sciences, College of Medicine, Princess Nourah Bint Abdulrahman University, Riyadh, Saudi Arabia
3 Department of Neurosciences, King Abdullah Bin Abdulaziz University Hospital, Princess Nourah Bint Abdulrahman University, Riyadh, Saudi Arabia
|Date of Submission||30-Dec-2020|
|Date of Acceptance||21-Feb-2021|
|Date of Web Publication||13-Apr-2021|
Department of Clinical Sciences, College of Medicine, Princess Nourah Bint Abdulrahman University, Riyadh, Saudi Arabia, Department of Neurosciences, King Abdullah bin Abdulaziz University Hospital, Princess Nourah bint Abdulrahman University, Riyadh
Source of Support: None, Conflict of Interest: None
Purpose: The aim of this study is to explore the use of sleeping aids among physicians in Saudi Arabia and its correlation with stress and insomnia during the COVID-19 pandemic. Materials and Methods: A sample of 1313 physicians was collected through an online cross-sectional convenience survey. The survey was E-mailed by the Saudi Commission for Health Specialties to the registered physicians in Saudi Arabia during the COVID-19 pandemic. It includes questions related to personal and sociodemographic characteristics, COVID-19, sleep-aid use, the Insomnia Severity Index, and the Perceived Stress Scale. Results: The participants were from various job levels (398 consultants, 1919 registrars, and 716 residents) and mainly from the central (38.2%) and Western (35%) regions. More than a third of them were using sleep aids (38.6%), which were mostly melatonin (75.7%). More than half of them had insomnia (67.1%), and the majority had moderate to high perceived stress (80.1%). Significant associations were found between insomnia and a number of personal and sociodemographic characteristics: Single status, young physicians, residents, smokers, and involvement in a COVID-19 management team. Other significant associations were found between stress and a number of personal and sociodemographic characteristics: Female sex, single status, young physicians, residents, working in the Ministry of Health, being on call 5–8 times/month, and involvement in a COVID-19 management team. Conclusions: Physicians in Saudi Arabia have had increased insomnia, stress, and use of sleep aids during the COVID-19 pandemic. Single, young physicians need more attention to support their psychological well-being.
Keywords: COVID-19, insomnia, physicians, sleep aids, stress
|How to cite this article:|
AlAteeq D, Almokitib A, Mohideen M, AlBlowi N, Fayed A, Alshahrani SM. Stress, sleep, and use of sleep aids among physicians during the COVID-19 pandemic. J Nat Sci Med 2021;4:197-204
|How to cite this URL:|
AlAteeq D, Almokitib A, Mohideen M, AlBlowi N, Fayed A, Alshahrani SM. Stress, sleep, and use of sleep aids among physicians during the COVID-19 pandemic. J Nat Sci Med [serial online] 2021 [cited 2021 Jun 13];4:197-204. Available from: https://www.jnsmonline.org/text.asp?2021/4/2/197/313648
| Introduction|| |
The COVID 19 pandemic is a global threat to health-care systems and economies. Worldwide, different countries have declared it as a national emergency with different degrees of public health measures. The pandemic has had tremendous effects on different countries' health-care systems, which have been challenged by an overload of patients and their requirements for intensive care and ventilators beyond the health system's capacity. Moreover, health-care workers have been facing a lack of personal protective equipment (PPE) and increased numbers of COVID-19 infections among them.
Physicians are dealing with different challenges and stressors, such as prolonged working hours, time limitations, and very demanding professions, which all might contribute to burnout., A study examined perceived stress among residents in Saudi Arabia and associated risk factors and found that stress levels among Saudi Arabia residents are comparable to or slightly higher than that reported among residents worldwide. The highest two risk factors are workload and sleep deprivation.
Work-related stress has been defined by the National Institute for Occupational Safety and Health as harmful physical and emotional responses that occur when the requirements of a job do not match the capabilities, resources, or needs of a worker. A Saudi study that was conducted among consultants found that they had moderate levels of perceived stress. Another Saudi study showed that stress was noticeably higher in residents than in administrative employees, which was strongly associated with multiple factors, including psychiatric disorders. In light of COVID-19, two recent studies were conducted among health-care workers in Saudi Arabia, which reported high levels of poor sleep quality, stress, depression, and anxiety.,
Sleep aids are medications that can be taken to facilitate sleep, including pharmacological prescriptions and over-the-counter pills. One study examined emergency physicians and found that 96% of them had used a sleep aid at least once during their career. Nonbenzodiazepine hypnotics were reported as the most commonly used, followed by alcohol and melatonin. However, none of the physicians had concerns regarding the negative impact on the quality of the health care they provide. Another study was done on the consumption of sleep-facilitating substances among members of the Canadian Association of Emergency Physicians, which found that a third of them had consumed sleep-facilitating agents at least once to help them sleep around a night shift.
We hypothesized that with all these stressors surrounding physicians, they would tend to solve their sleep problems through the use of pharmacological sleep aids. To our knowledge, there have been no local studies that assess the utilization of sleep aids among physicians. Thus, we aimed to explore the use of sleep aids among physicians and its correlation with perceived stress and insomnia during the COVID-19 pandemic in Saudi Arabia.
| Materials and Methods|| |
The data used in this study were collected by an online cross-sectional survey during the COVID-19 pandemic from April 13–23, 2020. This study was approved by the Institutional Review Board at Princess Nourah bint Abdulrahman University in Riyadh, Saudi Arabia. The coverage of the survey included the aims of the study and informed consent. Written informed consent was obtained.
This study was conducted on both male and female physicians from different levels (residents, registrars, and consultants). Both Saudi and non-Saudi nationalities were included from multiple specialties working in the Ministry of Health, university hospitals, and the military or private sectors from all regions in Saudi Arabia.
The Saudi Commission for Health Specialties (SCFHS) is the healthcare regulator for the Kingdom of Saudi Arabia and has a registry for all physicians. This organization is responsible for the supervision of training programs for all specialties and hospitals. An online survey was mailed by the SCFHS to 31,723 registered physicians.
Data collection and tools
The online survey included four sections. The first section consisted of questions related to personal and sociodemographic characteristics (sex, age, nationality, marital status, specialty, job title, working sector, number of shifts or on calls, psychiatric disorders, and alcohol abuse) and COVID-19 (personal diagnosis of coronavirus infection, role in treating corona patients, sleep aid use during the pandemic). The second section included 9 questions about sleep aid use, their types, the frequency of use, effects, and if they were prescribed or not.
The third section was the Insomnia Severity Index (ISI), which is a self-reported questionnaire that includes 7 items evaluating the nature, severity, and impact of insomnia during the past 2 weeks. It assesses multiple dimensions: Severity of sleep onset, sleep maintenance, early-morning awakening problems, sleep dissatisfaction, interference of sleep difficulties with daytime functioning, noticeability of sleep problems by others, and distress caused by the sleep difficulties. Every item is scored with a 5-point Likert scale (e.g., 0 = no problem; 4 = very severe problem), yielding a total score ranging from 0 to 28.
The total score was interpreted as follows: Absence of insomnia (0–7); sub-threshold insomnia (8–14); moderate insomnia (15–21); and severe insomnia (22–28). Previous studies have reported adequate psychometric properties for both the English and French versions of the ISI. The ISI also has good internal consistency among its items, as indicated by an overall Cronbach's alpha value of 0.85.
The fourth section was the Perceived Stress Scale (PSS), which was used to assess the participants' risk of stress. It has 10 questions for measuring perceptions of stress over the past month. Every item is scored with a 5-point Likert scale (e.g., 0 = never; 4 = very often), yielding a total score ranging from 0 to 40. Higher scores indicate higher levels of stress. The PSS had an overall Cronbach's alpha value of 0.82.
Data were analyzed using the Statistical Package for the Social Studies (SPSS 22; IBM Corp., New York, NY, USA). Descriptive statistics in terms of means, standard deviations, median, and interquartile ranges were used to describe the criteria of the studied sample. Quantitative data were analyzed with a t-test, and the association of qualitative variables was analyzed with a Chi-squared test. P < 0.05 were considered statistically significant.
| Results|| |
Personal and sociodemographic characteristics
As shown in [Table 1], a total of 1313 participants (398 consultants, 19 registrars, and 716 residents) completed the survey. The average age was 34.8 ± 9.5 years, and males were 55.8% of the participants. The majority were Saudis (97.1%) and married (58.3%). However, 49.4% had no children, and 25.6% had one or two children. Of the respondents, 38.2% were living in the central region, and 35% were from the Western region. The eastern region constituted 18.1%, and only 6.3% and 1.9% were from the northern and southern regions, respectively. Furthermore, 46.2% of the participants were employed in the Ministry of Health, while the remaining worked in military hospitals (20.4%), tertiary hospitals (17.4%), university hospitals (9.6%), and private hospitals (6.4%).
In regard to workload, 31.9% of the participants were on call 1–4 times a month, 26.4% were on call 5–8 times, 12.6% were on call more than 9 times, and 29.1% had no shifts or 19on-call times at all. More than half of our sample (52.2%) had 1–5 clinics per week, 31.5% had no clinics, and 16% had more than 6 clinics a week. Only 9 participants were diagnosed with COVID-19, and less than half (46.6%) were part of a team managing COVID-19 patients. More than half of the sample (53.4%) did not deal with COVID-19 patients. Smokers represented 24% of the participants, and only 3.7% had a history of alcohol or substance use.
Sleep aid use among physicians
As shown in [Table 1], sleep aid use was prevalent among 505 (38.6%) participants. However, most of them (81%) denied any current use for sleep aids. In addition, most of them (89.3%) had never sought professional advice for their sleeping problems, and 69.2% took sleep aids based on advice from a friend or relative or through self-prescription (24.4%). Only 6.4% of them obtained them from a prescription. Melatonin was the most commonly used sleep aid among physicians (75.7%), followed by antihistamines (10.6%).
Insomnia and perceived stress among physicians
[Figure 1] shows that there is a significant positive correlation between perceived stress and insomnia among physicians (r = 0.097, P < 0.01). [Table 2] displays the responses of the participants to the ISI items. In general, 67.1% of the physicians had insomnia ranging from mild (37.8%) to moderate (25.2%) and severe (4.1%). The mean value of the total ISI score was 10.85 ± 7.86 with an absolute range of 0–27.
|Figure 1: Correlation between perceived stress scale and insomnia severity intex|
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As shown in [Table 3], there were significant associations between insomnia level and a number of personal and sociodemographic characteristics: Age, marital status, job title, smoking, working in a COVID-19 management team, using sleep aids, and seeking medical advice for insomnia. Mild and severe insomnia was similarly reported by physicians of all ages, but moderate insomnia was significantly higher among those younger than 30 years compared to those in their thirties and above (29.3% and 22%, P = 0.019). Smokers reported moderate and severe insomnia more frequently than nonsmokers (26.3% and 7% vs. 24.8% and 3.2%, P = 0.023). Marital status showed a significant association with insomnia level as moderate insomnia was reported more among single physicians than those who were married and divorced (30.1% vs. 22.6% and 20.8%, P = 0.03). Mild insomnia occurred more among the divorced than married and single participants (47.2% vs. 37.6% and 36.6%, P = 0.03).
|Table 3: Univariate analysis of study variables and perceived stress and insomnia during the pandemic of COVID-19 (n=1313)|
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Residents had significantly more moderate insomnia than registrars and consultants (28.2% vs. 22.1% and 21.4%, respectively; P < 0.05). Registrars had more mild insomnia compared to residents and consultants (39.7% vs. 38% and 36.4%, respectively; P < 0.05). Involvement in a COVID-19 management team had a significant relation to insomnia, with physicians involved in management having significantly more severe insomnia than those physicians who were not involved in COVID-19 management (6% vs. 2.4%; P = 0.012).
Sleep aid use was significantly associated with insomnia. Severe and moderate insomnia was significantly higher among physicians who used sleep aids at least once in their life (7.3% vs. 2.1% and 36.6% vs. 17.9%, respectively, P < 0.01) and who were currently using sleep aids (11.6% vs. 2.3% and 52.6% vs. 18.8%, respectively, P < 0.01). Moderate and severe insomnia was reported significantly more among physicians who sought medical advice for insomnia (35.5% vs. 24% and 12.8% vs. 3.1%, respectively, P < 0.01), but mild insomnia was reported significantly more among physicians who did not seek medical advice (38.2% vs. 34%, P < 0.01).
[Figure 2] displays the responses of the participants to the PSS items. In general, 58.3% of the physicians had moderate stress, and 21.8% of them had high stress. The mean value of the total PSS score was 20.37 ± 7.86 with an absolute range of 0–40. As shown in [Table 3], there were significant associations between stress level and a number of personal and sociodemographic characteristics: Sex, age, marital status, number of children, job title, working sector, number of times on call per month, and working in a COVID-19 management team. Female physicians had significantly more moderate and high stress than males (60.2% and 27.8% vs. 56.8% and 17.1%, respectively; P < 0.01). Physicians who were younger than 30 years of age had significantly more high stress than those in their thirties and above (29.5% vs. 16.9%; P < 0.01).
Single physicians had significantly more high stress than married and divorced physicians (28% vs. 18.5% and 15.3%, respectively; P < 0.01). In addition, physicians with no children had significantly more high stress than those with 1–2, 3–4, and 5 or more children (27.5%, 20.8%, 13.2%, and 7.5%, respectively; P < 0.01). Furthermore, residents had significantly more high stress compared to registrars and consultants (28.9% vs. 18.1% and 10.8%, respectively; P < 0.01).
Physicians who were working in the Ministry of Health had significantly more high stress than those who were working in private, tertiary, military, and university hospitals (25.2% vs. 21.4%, 20.5%, 17.5%, and 16.7%, respectively; P < 0.01). Physicians who were on call 5–8 times per month had significantly more high stress than those who were on call 1–4, 9 or more, and 0 times (25.1% vs. 23.6%, 21.2%, and 17%, respectively; P = 0.021). Involvement in a COVID-19 management team had a significant relation to perceived stress. Physicians who were involved in a management team had significantly more high stress than those who were not (26.6% vs. 17.5%; P < 0.01).
| Discussion|| |
This is the first study in Saudi Arabia to investigate sleep aid use and its correlation to stress and insomnia among physicians during the COVID-19 pandemic. A literature review reveals few studies focusing on physicians from multiple specialties and levels in different regions of the country and different working environments. Many aspects can be affected by this pandemic, along with the huge workload faced by physicians.
Sleep and insomnia
We have found that more than two-thirds of physicians had insomnia during the pandemic (67.1%). Insomnia ranged from mild (37.8%) and moderate (25.2%) to severe (4.1%). Insomnia was more common among residents (70.5%) than consultants (61.6%) or registrars, which might be explained by the fact that residents are on call more times and have more clinics per week. However, about 30.4% of physicians were satisfied with their sleep.
Our study showed that physicians were more prone to insomnia, which may be due to more work stress during the COVID-19 pandemic and increased work shifts and duties. A recent Saudi study that was conducted among health-care workers during the pandemic found that 57.9% of them had sleep disturbance (trouble falling or staying asleep or sleeping too much). These results correlate with previous Saudi studies.
Alshahrani et al. conducted a study on health-care professionals, which revealed that shift workers have low sleep quality and higher daytime sleepiness than nonshift workers. Furthermore, Alhifzi et al. found that the majority of emergency physicians (83.8%) had poor sleep quality, which was linked to their night shifts. In Wuhan, China, a recent study found poor sleep quality among medical staff during the COVID-19 pandemic.
A high rate of moderate insomnia was noted among physicians younger than 30 years of age. This might be explained by the physicians gaining experience with successful sleeping habits as they advance in age and develop effective daily routines. Moreover, being a resident had an impact on the level of insomnia, with a higher level noted among residents. This is explained by their higher level of perceived stress. In this case, as well, physicians could be gaining an ability to accommodate their job and develop a suitable routine with time.
In regard to marital status, it was noted that the majority of single, married, and divorced physicians had mild insomnia. There was no difference noted regarding marital status, although single participants could be having considerably less stressful lives than those who are married, have children, and have other responsibilities apart from their job as physicians. In regard to smoking, higher percentages of mild and moderate insomnia were noted in those who are smokers. This finding could be explained by nicotine and nicotine withdrawal effects, which might trigger changes in neurotransmitters affecting sleep quality.
Among those who did not ever used sleep aids and those who are not currently using sleep aids, it was noted that most of them had mild insomnia, while most people who had used sleep aids before and those who are currently using them had moderate insomnia. This could be explained by the stressful life of physicians, which forces them to use sleep aids as a coping strategy to have a good quality of sleep. In addition, a higher percentage of those with moderate and severe insomnia sought medical advice, which could be related to the distressing effect that insomnia has on different aspects of their lives. Moreover, a higher prevalence of insomnia was noted among physicians who were involved in a team of COVID-19 management, which can be attributed to the high pressure and stress, which obviously will affect their sleeping patterns.
Sleep aid use
Physicians are assumed to be more prone to using sleep aids because of easy accessibility. In our study, we found that more than a third of physicians used sleep aids (38.6%), and 19% of them were using sleep aids during the COVID-19 pandemic. Only 6.4% obtained sleep aids by prescription. Melatonin was the most commonly used sleep aid (75.7%), which is generally safe for short-term use. Unlike other sleep aids, melatonin does not cause dependency or habituation. It is also easy to obtain, which makes it a more convenient choice.
We found that most of the physicians had moderate-to-high perceived stress (80.1%). We compared our study to a study on all health-care providers done in Bahrain, which examined sleep quality for frontline health-care workers during the COVID-19 pandemic. It was reported that 85% had moderate-to-severe stress, which was a higher percentage of stress than in our study. This most likely occurred because they were assessing the stress levels of multiple health-care workers and not only physicians.
Female nurses were the majority of their participants, and it is well known that nurses have more stressors than physicians since most of the time, they are the first-line health care workers, and they spend more time with patients, particularly those who are admitted. This puts them in high stress related to being infected or sometimes insulted by patients or their families. Their study showed that female sex was a predictor of stress, which was a common point with our study.
Compared to other studies conducted on a specific job category, it was found that the PSS score was similar to that in our study. For example, a study on residents in Saudi Arabia assessed stress and its determinants. Al Osaimi et al. reported that among 938 residents, the mean PSS was 22.0, which showed that stress was connected to work overload and a lack of sleep. They concluded that the risk of perceived stress was the same or higher in Saudi Arabia residents as compared to residents in other parts of the world. Another study done on consultants in Saudi Arabia concluded that among 582 consultants, the mean PSS was 17.7, and high-stress levels were connected to the female sex, young age, and Saudi nationality.
Moreover, high-stress level was noted among single physicians, which could be explained by the effects of a lack of a supportive spouse. In addition, residents had significantly higher stress than registrars and consultants, which might be explained by their short experience and more requirements, like examinations and research. Furthermore, physicians who were on call 5–8 times per month had significantly more high stress than those who were on call 1–4, 9 or more, and 0 times. This can be attributed to the exhausting 24-h work day of those on call and the sleep deprivation that occurs when on call.
Physicians who were working in the Ministry of Health had significantly more high stress than those who were working in private, tertiary, military, and university hospitals. This can be attributed to the eligibility for treatment at Ministry-of-Health hospitals, which cover all Saudi and non-Saudi citizens, as well as the high load of patients. University hospitals had the lowest stress levels, which is explained by the educational environment and presence of interns who can help in the documentation. Finally, being in a COVID-19 management team significantly increased stress among physicians, which could be explained by the fear of contracting the virus or transmitting it to their families.
Our study is considered the first Saudi survey to investigate sleep aid use and its correlation with stress and insomnia among physicians, but there were multiple limitations. First, it is cross-sectional and reflects a short period regarding the effect of the COVID-19 pandemic on sleep quality, use of sleep aids, and work stress. Second, this design is not able to make a causal association. Third, reporting bias is possible due to the self-reported survey. Finally, our study may not be reflective of all physicians in Saudi Arabia due to the low response rate and the convenience sampling.
| Conclusions|| |
We have concluded that physicians in Saudi Arabia have increased insomnia and use of sleep aids during the COVID-19 pandemic. This might be due to increased work stress, work shifts, and duties. Since insomnia could be related to stressors in physicians' lives, we recommend that medical institutions focus more on applying sessions for dealing with hospital stressors, preferably in a more convenient way like online or without fees so that they can be available for everyone.
We also recommend that physicians and health-care workers, in general, adopt a healthy lifestyle. Quitting smoking is highly encouraged due to the bad influence of smoking on people's health and life quality. Moreover, we recommend that concerned institutes and program directors implement support programs targeting junior residents through the experience of seniors. Asking for help should be encouraged in the healthcare sector, and psychological consultations should be facilitated for individuals in need. The COVID-19 pandemic has had a tremendous impact on physicians' stress levels, and appreciation should be shown for frontline workers' efforts with rewards and leave.
Financial support and sponsorship
This research was funded by the Deanship of Scientific Research at Princess Nourah bint Abdulrahman University through the Fast-track Research Funding Program.
Conflicts of interest
There are no conflicts of interest.
| References|| |
Tanne JH, Hayasaki E, Zastrow M, Pulla P, Smith P, Rada AG. Covid-19: How doctors and healthcare systems are tackling coronavirus worldwide. BMJ 2020;368:m1090.
Veasey S, Rosen R, Barzansky B, Rosen I, Owens J. Sleep loss and fatigue in residency training a reappraisal. JAMA 2002;288:1116-24.
Zis P, Anagnostopoulos F, Sykioti P. Burnout in medical residents: A study based on the job demands-resources model. ScientificWorldJournal 2014; 2014, Article ID 673279. doi: 10.1155/2014/673279.
Al Osaimi FD, Kazim SN, Almufleh AS, Aladwani BS, Alsubaie AS. Prevalence of stress and its determinants among residents in Saudi Arabia. Saudi Med J 2015;36:605-12.
Exposure to Stress Occupational Hazards in Hospitals; 2008. Available from: https://www.cdc.gov/niosh
. [Last accessed on 2020 Sep 27].
Alosaimi FD, Alawad HS, Alamri AK, Saeed AI, Aljuaydi KA, Alotaibi AS, et al
. Patterns and determinants of stress among consultant physicians working in Saudi Arabia. Adv Med Educ Pract 2018;9:165-74.
Alosaimi FD, Alghamdi AH, Aladwani BS, Kazim SN, Almufleh AS. Work-related stress and stress-coping strategies in residents and administrative employees working in a tertiary care hospital in KSA. Taibah Univ Med Sci 2016;11:32-40.
Jahrami H, BaHammam AS, AlGahtani H, Ebrahim A, Faris M, AlEid K, et al
. The examination of sleep quality for frontline healthcare workers during the outbreak of COVID-19. Sleep Breath 2020;1-9. doi: 10.1007/s11325-020-02135-9.
AlAteeq DA, Aljhani S, Althiyabi I, Majzoub S. Mental health among healthcare providers during coronavirus disease (COVID-19) outbreak in Saudi Arabia. Infect Public Health 2020;13:1432-7.
Francis MN, Wishart IM, Williamson T, Iverach R. Use of pharmacologic sleep aids and stimulants among emergency medicine staff physicians in a Canadian tertiary care setting: A web-based survey. Ann Emerg Med 2019;73:325-9.
Bailey B, Alexandrov L. Survey to describe sleep-facilitating substances used by Canadian emergency physicians. Can J Emerg Med 2005;7:93-9.
Bastien CH, Vallières A, Morin CM. Validation of the Insomnia Severity Index as an outcome measure for insomnia research. Sleep Med 2001;2:297-307.
Cohen S, Williamson G. Perceived stress in a probability sample of the United States. In: Spacapan S, Oskamp S, editors. The Social Psychology of Health. Newbury Park, CA: SAGE; 1988. p. 31-67.
Alshahrani SM, Baqays AA, Alenazi AA, AlAngari AM, AlHadi AN. Impact of shift work on sleep and daytime performance among health care professionals. Saudi Med J 2017;38:846-51.
Alhifzi S, Al-Ghonimy A, Al Aboudi M, Al Abdullah R, Olaish A, BaHammam A. Assessment of sleep quality, daytime sleepiness, and depression among emergency physicians working in shifts. Nat Sci Med 2018;1:17-21.
Xiao H, Zhang Y, Kong D, Li S, Yang N. The effects of social support on sleep quality of medical staff treating patients with coronavirus disease 2019 (COVID-19) in January and February 2020 in China. Med Sci Monit 2020;26:e923549.
Li H, Liu Y, Xing L, Yang X, Xu J, Ren Q, et al
. Association of cigarette smoking with sleep disturbance and neurotransmitters in cerebrospinal fluid. Nat Sci Sleep 2020;12:801-8.
[Figure 1], [Figure 2]
[Table 1], [Table 2], [Table 3]