Sleep quality and anxiety among nurses in tertiary hospitals in China and the influencing factors: A cross-sectional study

The purpose of the study was to investigate to understand the situation of sleep quality and anxiety among nurses in tertiary hospitals in China, and analyze their influencing factors. A cross-sectional survey was performed for nurses in Beijing tertiary hospitals including Beijing Tongren hospital, Beijing Anzhen Hospital and Beijing Children Hospital. The Pittsburgh Sleep Quality Indes (PSQI) and Zung Self-Rating Anxiety Scale (SAS) were used to measured the sleep quality and anxiety symptoms, respectively. Survey of quality of life in nurses was measured by 36-item Short Form Health Survey (SF-36). Spearman’s correlations analysis and logistic regression analysis was used to understand the influencing factors with sleep disorder, anxiety symptoms and quality of sleep. Quality of life (both PCS and MCS) were affected by influencing factors including marital status, working years, education background, income monthly, working hours, regular diet, physical exercise, sleep disorder, anxiety symptoms, felling of stress, and stress from economic, social, occupational. by some Correlation between was positive for nurses.

hinted that promotion of health lifestyle, effort-reward balance and providing social support may be significant to decrease the poor sleep quality and anxiety symptoms and increase quality of life in nurses.

Background
The status of physical and mental health have important effect for quality of life and work for medical staffs [1]. Clinical nurses, as an important medical group, maintain faster work pace and heavier workload for a long time that increase the risk of physical and mental health problem, including feeling stress, fatigue, burnout, anxiety, and decreasing the quality of life. However, as a negative result, poor sleep quality has becoming an obvious and complaint problem for nursing staff all over the world [2][3][4][5]. Shift work disorder, stressful workload and complex work environment had been studied that may be the main reasons of sleep problems for nurses [2,3,4,6].Poor sleep quality has negative effects for physical health such as metabolic disturbance, cardiometabolic disorders and chronic diseases [6][7][8][9][10].
Moreover, sleep problems for a long time also could result in serious effects for psychology and mental health including thought retardation, low spirit, irritability, depression and so on [11,12]. In fact, apart from impacting health of nurses, the previous studies have been improved that poor sleep quality could decrease the work performance and increase the risk of medical errors, impaired psychomotor performance over the past 40 years [13][14][15][16][17][18].
As we know, anxiety is an unpleasant emotion characterized by fear, worry, rumination [19].However, anxiety disorder is medical disease if it was persistent and intense [19]. Anxiety disorder has become a worldwide problem that we need focus on. Previous researches reported that one-eighth population of world may suffer from inappropriate anxiety [20].Some influencing factors were supposed like women,older age, urban,obese,and so on [21][22]. Previous studies also have indicated that nurses was a higher risk professional group that with anxiety disorder that others, 21% of Singapore general hospital nurses,20% of ICU and general care nurses in the US, 43.2% of shift-work nurses in Iranian have suffered from anxiety disorder, respectively [23][24][25].
Chinese hospitals are divided into three degrees(tertiary hospital;sencod-class hospital; class-I Therefore, nurses in Chinese tertiary hospitals were faced with heavy workload, stressful work environment and complex interpersonal relationship. Chinese studies indicated that the quality of life of nurses in Chinese tertiary hospital was facing great challenge [6,[27][28].
Previous researches have shown that we should pay more attention to physical and mental health of clinical nurses.Nurses are encountering more stressful job and workload in tertiary hospital than that in secondary and first-level hospitals. Not only that, they were more possibility and risk for physical and mental health and medical errors. However, we do not know that clearly. Then, the purpose of our study was understanding the status and influencing factors of sleep quality, source of stress, mental health, quality of life and their correlation among nurses in tertiary hospitals in China. We also hope to offer some suggestion for improving their quality of life and work.

Methods Participants
We selected three famous tertiary hospitals in China locating in Beijing into our cross-sectional survey that a lot of patients all over China were coming because of their high quality of medical care, including Beijing Children hospital,Beijing Tongren Hospital, and Anzhen hospital. We have surveyed 643 nurses by self-administered questionnaire from April to June in 2018, and 517 questionnaires were returned valid(80.4%). These 517 nurses were becoming our participants in our study.

Survey Questionnaire
Our self-administered questionnaire consisted of five parts, including survey of basic information, source of stress, quality of sleep, anxiety and quality of life.

Basic Information And Source Of Stress
The basic information of study contained sex; age; marital status; seniority; education level (junior college degree or below, bachelor degree or above); professional status ( primary, intermediate or above); monthly income; working hours per week, smoking, drinking, regular diet and physical exercise. We understood the subjective feeling of source of stress by the question "what do you think the main source of your stress? Economic stress, occupational stress, social stress, or other reason".

Quality Of Sleep
The Pittsburgh Sleep Quality Index(PSQI) is a valid and widely instrument to measure and assess the quality of sleep for the general and clinical populations over a 1-month period [29,30]. The Chinese version of Pittsburgh Sleep Quality Index(C-PSQI) had an good reliability and sensitivity using cutoff value of 5 that discriminate poor from good quality of sleep [30]. C-PSQI contain 19 items that are combined into 7 component scores including subjective sleep quality, sleep latency, sleep duration, habitual sleep efficiency, sleep disturbance, used sleep medication, daytime dysfunction [30]. The range of global score is from 0 to 21 summing 7 component scores, and higher scores represent the subjective quality of sleep is poorer [6,29,30].

Anxiety
We measured the anxiety symptoms of our participants by the Zung Self-Rating Anxiety Scale(SAS) that has an good internal consistency and test-retest reliability [31][32][33]. There are 20 items gathered the scale, and every item has 4 options that scored different scores. The range of total raw score is from 20 to 80,or index score is from 25 to 100.The upper limit for the normal was a raw score 40 or index score 50, respectively. A higher score indicate higher level of anxiety symptoms. The study used the index score to measure the anxiety symptom. When the total index score ≥ 50 was defined as "mild anxiety symptom", ≥ 60 that was moderate anxiety, ≥ 70 was severe anxiety according to Chinese version [34].

Quality Of Life
In the study, we selected the 36-item Short Form Health Survey (SF-36) to evaluate the quality of life (QOL) for our participants. The SF-36 is also a reliable and effective measuring tool to assess QOL of patients and occupational populations [35][36].

Characteristics of participants
All the participants of our study were female, and their average age was 30.49 ± 7.53 years. The average PSQI score was 7.71 ± 3.62, including 372 participants that scores were above 5 (72.0%). The average SAS score was 45.18 ± 9.90,including 157 participants with a SAS score 50 ( Table 1 showed the results that different factors affected the quality of sleep. The nurses' sleep quality were affected by some factors including income monthly, working hours, regular diet, physical exercise, stress from economic, social, occupational. However, we did not find the marital status, working years, education background, professional title, leader, smoking and alcohol consumption were significantly related to quality of sleep.

Influencing Factors Analysis Related To Anxiety Symptoms
Results of influencing factors analysis showed education background, income monthly, working hours, regular diet and economic stress, social stress, occupational stress have significantly related to anxiety symptoms. Whereas marital status, working years, professional title, leader, smoking, alcohol consumption and physical exercise were not. The results were showed in Table 2.
Influencing Factors Analysis Related To Quality Of Life Table 3 indicated quality of life (both PCS and MCS) were affected by influencing factors including marital status, working years, education background, income monthly, working hours, regular diet, physical exercise, sleep disorder, anxiety symptoms, felling of stress, and stress from economic, social, occupational. However, smoking, alcohol consumption and leader were not. Professional title was significant related to MCS, but not to PSC.

The Relationship Between Sleep Disorder And Anxiety Severity
Correlation between sleep disorder and anxiety severity was positive for nurses. The result was showed in Table 4. Table 5 showed that physical exercise, regular diet and income monthly have independent influence with sleep disorder for nurses. In other words, physical exercise frequency, keeping regular diet and salary suitably were positive factors for preventing sleep disorder for nurses. Table 6 showed that anxiety symptoms revealed an independent relevance with education background, working hours, regular diet, economic stress. In other words, the risk factors for anxiety in nurses were higher education background, longer working hours, irregular diet and economic stress.    Table 6 Logistic regression analysis of multiple factor influencing anxiety symptom

Discussion Prevalence and influencing factors of sleep disorder among nurses in tertiary hospitals
Under the environment of long-term heavy workload, shift work system and high requirement of work quality, health care workers were lower status of physical and mental health than other groups. As a typical physical problem, Sleep disorder has become the focus of attention. According to our results and previous studies, the overall prevalence of sleep disorder in hospital staffs was higher than the general population [6,[37][38][39][40]. However, the status in nurses was even more serious. A pilot study in Urumqi(Xinjiang,China) using PSQI to evaluate the quality of sleep in physicians, indicated 59.92% participants had sleep disorders [41], that was lower than our results. The Other researcher in Tehran(Iran) and Taiwan(China) also revealed that nurses had higher incidence rate than other health care workers [42][43]. However, as a high-risk group, compare to other health care workers, nurses were most likely to suffer from sleep disorder that be focused first.
The previous study found highly stress correlated positively with sleep disorder [6,44].In our study, nurses had sleep disorder with felling economic, occupational and social stress. Nurses in tertiary hospitals need deal with different kinds of medical condition, keep learning new medical knowledge and solving different social relationship problem. In fact, nurses always be exposed to high level stress for a long time [45][46].The percentage of nurses (working hours 40H per week) was 49.6% in our study. The previous studies indicated that heavy workload and longer working hours squeeze time for rest and exercise, and made nurses felling highly stress which influence quality of sleep [6].
However, along with the rapid rhythm of work and work time uncertainty, nurses develop a habit of irregular diet and exercise that affect the circadian rhythms which decrease the quality of life [2].

Prevalence and influencing factors of anxiety symptoms among nurses in tertiary hospitals
The prevalence of anxiety symptoms in nurses was 30.4% in our study that converged towards the results of similar studies [27,[47][48][49]. However, the prevalence in medical students and doctors were 12.5% and 21.1%, respectively [50][51]. The previous studies indicated, nurses were risk group of anxiety symptom in health care workers. Comparing with other populations in China, the prevalence was obvious higher [52][53]. According to the fact, it was warranted to in-depth studies and active interventions about anxiety symptoms in Chinese nurses.
Our study found higher education backgrounds was risk factor about anxiety symptom in nurses. The results of Liaoning general hospital also indicate nurses with higher education backgrounds may more likely be anxiety symptoms [27]. The results may reflect nurses with higher education backgrounds have higher learning and working target and demand. The previous study indicated nurses with regular meals have lower anxiety symptom(OR 0.719)that was similar with our study [27]. Keeping healthy lifestyle may be helpful for reducing anxiety symptoms in nurses. Longer working hours, heavier workload and lower salary make effort-reward imbalance in nurses that have negative effect for mental health and their job satisfaction [27,[54][55] however, a lot of researches have shown that the status of stress was significantly related to physical and mental health, including anxiety symptom [56][57].
The correlation between sleep disorder and anxiety symptoms that influence the quality of life Several previous studies indicated sleep disorder have position relation with anxiety symptoms [58][59]. We also find the strong correlation between sleep disorder and anxiety symptom.
We think there maybe correlation between physical health and mental health that the previous similar studies shown the same viewpoint [60].We also found nurses with sleep disorder or anxiety symptoms Hospital, and Capital Medical University Affiliated Anzhen Hospital. All the participants were orally informed after our researchers had introduced the study. Written informed consent concerning conduct of the survey was obtained from each respondent before data collection. Confidentiality and privacy were maintained by using unique identification numbers instead of names.

Consent for publication
Not applicable

Availability of data and material
The datasets used and/or analyzed during the current study are available from the corresponding author on reasonable request.

Competing interests
The authors declare that they have no competing interests.

Funding
Financial support was provided by Key consulting projects of Chinese academy of engineering

Authors' contributions
DW and DH designed the study and questionnaire. JL,MH and HY collected the data and control the quality of study. DW and YP analyze the date and wrote the manuscript. DH supervised the study and data analysis. All authors read and approved the manuscript.