Participants and setting
Adult outpatients were recruited from the psychological departments of First Affiliated Hospital of Nanjing Medical University in Jiangsu province of China between May 2019 and December 2019. Eligible participants met Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) diagnostic criteria for chronic insomnia disorder . Adult healthy volunteers were recruited from the Health Management Centre of this hospital as healthy controls. All patients and controls underwent detailed history taking. All subjects with the following conditions were excluded: (a) irregular sleeping patterns, (b)history of diagnosis of alcohol or substance abuse/dependence in the last 6 months, (c) use of antidepressants or antipsychotics, (d) pregnancy for women, (e)other mental disorders, (f) serious physical illness, (g)physical or psychological impairments that prevented from completing the questionnaires. The participants were assessed to determine their sleep quality, coping style, and psychological distress using interviewer-assisted and self-report methods.
Sociodemographics And Lifestyle Data
Demographic data (age, gender, marital status, body mass index (BMI), and education level) and lifestyle information (smoking and consumption of alcohol) were recorded in all patients and controls. Tobacco and alcohol use was divided into never/rare and regular use (more than once a week). In addition, the course of illness of patients was recorded.
Sleep Quality Assessment (psqi)
A Chinese version of the PSQI questionnaire was used to assess the patient’s sleep quality. The PSQI questionnaire consisted of 19 self-rating items that can be categorized into seven components, including subjective sleep quality, sleep latency, sleep duration, habitual sleep efficiency, sleep disturbance, used sleep medication, and daytime dysfunction. The score of each component score was rated from 0 to 3. The sum of these seven component scores provided a global PSQI score, which ranged from 0 to 21. Higher scores indicate poorer sleep. The Chinese Version of PSQI was translated and validated by Liu et al. . In that study, the internal consistency Cronbach’s α was 0.84, the split-half reliability was 0.87, and the 2-week test-retest reliability was 0.81.
Assessment Of Coping Styles
The Simplified Coping Style Questionnaire (SCSQ) is a 20-item self-report scale that measures individual coping style. The SCSQ was divided into two subscales: positive coping (12 items) and negative coping (8 items). Positive coping reflects the level of the active coping style, such as “solving problems by work, learning or other things” or “looking at the good side of things”. In contrast, negative coping reflects the level of passive coping style, such as “when facing problems, escaping troubles by drinking and smoking” or “relying others to solve problems”. Each item is scored on a four-point Likert scale (0 = never, 1 = seldom, 2 = often, 3 = always). Higher scores on each subscale reflect the level of the coping style. Cronbach's α for positive coping and negative coping were 0.89 and 0.78, respectively.
Evaluation Of Psychiatric Distress And Lifestyle Factors
Psychiatric distress was estimated using the Chinese version of SCL-90R. The SCL-90R is a self-reporting, clinical symptom rating scale consisting of 90 items. Responses indicate symptoms associated with 9 symptom dimensions, which included somatization, obsessive-compulsive, interpersonal sensitivity, depression, anxiety, hostility, phobic anxiety, paranoid ideation, and psychoticism. Additionally, a global symptom score is calculated. The Chinese-version SCL-90R questionnaire with established reliability and validity is widely used in measuring psychological distress in Chinese clinical practice and research. In a recent study carried out in patients with alopecia areata, the internal consistency Cronbach’s α was 0.98 and split-half coefficient was 0.95.
SPSS version 22.0 (SPSS, Inc., Chicago, IL, USA) statistical software was used for all data analyses. Measurement data are mean ± standard deviation (SD). Various sociodemographic variables, coping style parameters and psychological factors between insomnia patients and healthy controls were assessed by independent sample t test. For categorical variables, the chi-square test was used for comparisons between the two groups. The correlations between variables were assessed by Spearman correlation analysis. To explore the independent influencing factors of sleep quality, multiple stepwise regression analysis was applied. A two-tailed P value < 0.05 was considered statistically significant.