Investigation methods
We extracted one district and one county from each city, which ensured that urban population and rural population were both investigated. Subjects were convenient sampled as clusters from urban or rural community in May to June 2019. Participants which aged from 18 to 90 and could read and complete the questionnaire were recruited. Spot field questionnaire survey were conducted by trained investigators. Data were collected anonymously.
The study was conducted in accordance with the Helsinki declaration and approved by the Ethics Committee for Medical Research, School of Public Health, Fudan University.
Written informed consent was obtained from all participants or their legal guardians before investigation. The questionnaire used in our study was developed for this study. An additional file shows the English language version of the questionnaire in more detail [see Additional file 1].
The questionnaire contained sociodemographic characteristics, lifestyles, health status, disease history and self-reported sleep quality.
Sociodemographic characteristics include sex, age, marital status, educational level, personal monthly income, and family monthly income. Body mass index (BMI) is calculated by weight(kg) / height2(m2) and categorized into 4 groups [14].
Lifestyle factors include physical activities, smoking, alcohol drinking, having breakfast, eating vegetables, eating fruits, square dancing, daily screen time, using electronic devices before sleep, time of exposure to sunlight. Physical activities is measured by average times of at least 30 minutes of physical activity (physical activity of moderate intensity or above, such as brisk walking, running, swimming, dancing, cardio, football, basketball, climbing, etc.) per week. Smoking is measured by average number of cigarettes smoked each day. Alcohol drinking is measured by frequency of drinking. Having breakfast is measured by average times of having breakfast per week. Eating vegetables is measured by average weight of vegetables you have each day which excluded starchy vegetables such as potato, yam, taro, etc. Eating fruits is measured by average times of eating fresh fruits per week which excluded canned fruit, preserved fruit, etc. Square dancing is defined as clustered dance in outdoor places such as parks in China and measured by average times per week. Daily screen time is measured by average time of daily use of electronic devices such as cellphone, television and computers. Using electronic devices before sleep is defined as using electronic devices between bedtime and 30 minutes before bedtime, and measured by how often. Time of exposure to sunlight is measured by daily average sunlight exposure time (minutes) in the last month.
Subjects were asked the degree of concerning about their own health and self-reported health status.
We also measured whether they were suffering from chronic noncommunicable diseases which were diagnosed by a doctor. Chronic diseases in our study included hypertension, diabetes, hyperlipidemia, heart disease (such as coronary heart disease, rheumatic heart disease, cardiomyopathy, congenital heart disease, pulmonary heart disease and so on), respiratory diseases (such as impaired lung function, chronic obstructive pulmonary disease, asthma and so on), stroke (such as transient ischemic attack, ischemic stroke, hemorrhagic stroke and so on), malignant tumor, hyperuricemia, musculoskeletal diseases (such as osteoarthritis, rheumatoid arthritis and so on).
Measurement of sleep quality
Self-reported sleep quality (hereinafter referred to as sleep quality) was used with a 5-ordinal-categorized answer, which means that answer 1 to 5 correspond with very good, good, general, bad and very bad, respectively.
According to diagnosis of insomnia in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-V)[15], Participants were asked the following questions to get more sleep information:
-
In the last month, the frequency of difficulty initiating sleep for at least 30 minutes;
-
In the last month, the frequency of difficulty maintaining sleep, waking more than 3 times in a night;
-
In the last month, the frequency of awakening earlier than usual in the morning, at least 30 minutes early, with inability to return to sleep;
-
In the last month, the frequency of feeling sleepy during the day;
-
How long have you had one of above sleep problems (difficulty initiating sleep, difficulty maintaining sleep, awakening early)?
-
In the last month, have you take medication (e.hypnotics such as benzodiazepines or to help you sleep?
Statistical analysis
Data entry was completed by Epidata 3.1 and statistical analysis was performed by SAS 9.4 (Copyright by SAS Institute Inc., Cary, NC. Licensed to FUDAN UNIVERSITY). The significance level was set at 0.05. Continuous variables were described as mean and standard deviation (SD), and categorical variables were described as frequencies and percentage (%).
Logistic regression analysis was used to estimate the effect of influencing factors on sleep quality, crude odds ratio (cOR) and adjust odds ratio (aOR) and their 95% confident intervals (CI) were calculated. Self-reported sleep quality was categorized as good sleep quality (y = 0) and bad sleep quality (y = 1). Answer 1 to 3 (very good, good, general) was categorized as good sleep quality, answer 4 and 5 (bad and very bad) was categorized as poor sleep quality. The variables including personal monthly income, family monthly income, degree of concerning about their own health, self-reported health status, take medication (i.e. hypnotics), physical activities, smoking, alcohol drinking, having breakfast, eating vegetables, eating fruits, square dancing, daily screen time and using electronic devices before sleep were treated as continuous variables in logistic regression.