Participants
This study included two clinical and non-clinical samples. The clinical sample (n =120) were recruited from the Sleep Disorder Clinic of Baharloo Hospital in Tehran, during the period from September 2016 to July 2017. Participants were included if they would meet the DSM-V criteria (sleep initiation, sleep maintenance, or early morning awakening problems which occurs three times per week, lasting for at least three months and makes clinically significant distress) for insomnia disorder (1). Individuals diagnosed by other sleep disorders (e.g. sleep apnea, restless leg syndrome), severe psychiatric disorders (such as bipolar disorder), substance abuse problems, and instable use of sleep or psychotropic medications were excluded. Non-clinical group (n = 110) were good sleepers who were recruited from the study announcements at different locations. They met Research Diagnostic Criteria (RDC) for Normal Sleepers (27). Of the total sample that was primarily invited to participate, less than 20% (n = 19) refused to participate. Fifty-three percent of the clinical sample and 58% of the non-clinical sample were female. In clinical group, 37.4% of the sample identified their education level as diploma, 39.4 as bachelor, 20.6% as master, and 2.6% as Ph.D. In non-clinical group, 41.2% of the sample identified their education level as diploma, 35.6 as bachelor, 19.8% as master, and 3.4% as Ph.D. The clinical sample had an average age of 39.20 years (SD = 5.61, range: 18-71) and the non-clinical sample had an average age of 36.5 (SD = 4.82, range: 18-72). The insomnia duration mean of the clinical sample was 8.42 years (SD = 7.41) with an age mean of 29.64 years (SD = 14.23).The average sleep onset latency (SOL), total time of awakenings after sleep onset (WASO), early morning awakening (EMA), total actual sleep time (TST), and total time spent in bed (TIB) as gleaned from the sleep diary were 97.31, 115.26, 48.61, 358.2, and 619.8 minutes, respectively. In addition, sleep efficiency of the clinical group was 57.8%.
Measures
Glasgow Sleep Effort Scale (GSES)
This scale consists of 7 items and it was developed by Broomfield and Espie (2005). This scale assesses a present state of sleep effort. Responses are recorded on a 3-point Likert scale from not at all (0), to some extent (1), very much (2). Higher scores indicate greater effort to sleep over the past week. An item example is “I make too much of an effort to fall asleep, when it should happen naturally”. Psychometric properties of this scale has been examined in insomniac patients and good sleepers (19). Results showed that GSES had adequate internal consistency (Cronbach’s Alpha = .77) and it can differentiate good sleepers from insomniac patients appropriately (19).
Dysfunctional Beliefs and Attitudes about Sleep Scale-10 (DBAS-10)
This scale assesses dysfunctional cognitions and beliefs about sleep and it was developed by Espie, Inglis, Harvey, and Tessier (2000). Each item is rated from 0 to 10 which higher scores indicate stronger agreement with dysfunctional beliefs. An item example is “I need 8 hours of sleep to feel refreshed and function well during the day”. Internal consistency of DBAS-10 in terms of Cronbach Alpha is .69 and it can differentiate good sleepers from insomniac patients. Factor analysis of DBAS-10 demonstrated 3 factors including: Beliefs about the immediate negative consequences of insomnia (5 items), Beliefs about the long-term negative consequences of insomnia (3 items) and Beliefs about the need for control over insomnia (2 items) (28). In an Iranian clinical sample (n =120), test-retest reliability of DBAS-10 for 2-weeks’ time interval was .83% and its internal consistency was .82% (29).
Depression Anxiety Stress Scale (DASS-21)
DASS-21 (30) is a short form of DASS-42 (31) designed to measure symptoms of depression, anxiety and stress in adults. Respondents are asked to indicate the extent to which each of the statements is applied to them on a 4-point Likert scale starting from never (1) to always (4) (31). This scale has demonstrated appropriate convergent, discriminant and construct validity (30). Also, a study conducted on an Iranian sample of college students (n = 638) reported test-retest reliability of .81, .78 and .80 and Cronbach Alphas of .85, .75 and .87 for depression, anxiety and stress of this scale respectively (32).
Pittsburgh Sleep Quality Index (PSQI)
This is a 19-item index consisting of 7 components and was developed by Buysse, et al (1989). The components are subjective sleep quality, sleep latency, sleep duration, habitual sleep efficiency, sleep disturbances, use of sleep medication, and daytime dysfunction. Individuals rated each item on a 4-point scale from 0 to 3. Cronbach Alpha and test-retest reliability of this scale were reported as .83 and .85, respectively (33). This scale previously has been examined on an Iranian sample and the Cronbach Alpha was reported .52 for patient group (n =125) and .78 for control group (n = 133). Also, the sensitivity and specificity of the Persian version were reported .94.5 and .72 respectively (34).
Insomnia Severity Index (ISI)
This is a 7-item scale which was developed by Bastien, Vallieres, and Morin (2001). The items measure the severity of problem in going to sleep, staying asleep, waking up too early, satisfaction with sleep, noticeability of sleep problem, distress and interference caused by sleep problem. Total score of this scale ranges from 0 to 28, which higher scores indicate more perception of insomnia. Cronbach Alpha of the scale in insomniac patients was .74 and it consists of three components: Impact (3 items), severity (3 items), satisfaction (3 items) (35). Cronbach Alpha of this scale for a group of Iranian patients was .82 and its item-total correlation coefficient was reported from .56 to .91 (36).
Pre-sleep Arousal Scale (PSAS)
This scale includes 16 items and it was developed by Nicassio, Mendlowitz, Fussell, and Petras (1985) to assess both cognitive and somatic components of arousal. Participants are asked to rate each item from 1 (not at all) to 5 (extremely) (37). Test-retest reliability of the scale in a sample of college students (n = 30) has been .72 and .76 for cognitive and somatic components respectively. Also, Cronbach Alpha of cognitive and somatic components were .67 and .84 for normal sleepers and .76 and .81 for insomniacs respectively (37). Cronbach Alpha of the Persian version in a sample of college students was .72 for somatic and .84 for cognitive subscale. Test-retest reliability of the scale in two week time interval was .88 (38).
Consensus Sleep Dairy (CSD)
Sleep diary is a self-report scale that gathers information about pattern and quality of sleep over two weeks (39). CSD has three versions as the core (includes a standard set of 9 items), the expanded for the morning (includes optional morning completion items), and the expanded for evening (includes optional morning and evening completion). It assesses sleep onset latency, wakefulness after sleep onset, terminal WASO, total wake time, time in bed, and total sleep time (40). Validity, usability, and clinical utility of the scale is proved previously (41). Core version of the CSD was used in the current study.
Procedure
The study was approved by the ethics committee at Tehran University of Medical Sciences [Ethics code: IR.TUMS.REC.1396.2947]. All participants provided written informed consent before their participation. They were informed that their participation in the study is completely voluntarily. They could withdraw at any time without restriction. In addition, they were informed that only the research team will have access to the data for academic purposes and the data will be treated confidentially and anonymously.
The English version of GSES was carefully translated into Persian by a group of specialists, including two psychiatrists, three sleep clinicians and two clinical psychologists. The translated version was back-translated to English by two linguistics. Following that, a bilingual individual compared the back-translated and original versions of the scale to check the quality and precision of the back-translated version based on the original one. This led to the finalized Persian version of this scale. To avoid any potential misunderstanding in regard to wording, the current Persian version was piloted with 30 participants, who were asked to rate readability and clarity of the Persian items on a response scale ranging from 0 (not understandable) to 5 (completely understandable). Over 95% of the participants chose the “completely understandable” which indicated no need for further item revisions.
The clinical group included individuals who were seeking treatment at sleep disorders clinic of Baharloo hospital in Tehran. Non-clinical group were good sleepers who responded to study announcements and they were invited via e-mail. Regarding the clinical group, those who volunteered were interviewed by a sleep medicine specialist to evaluate the inclusion criteria. Then, the eligible participants were asked to complete a sleep diary for 2-weeks with the aim to evaluate if they have SOL or WASO more than 30 minutes. After that, participants were referred to a clinical psychologist and were asked to complete the study measures. The data collection consisted of CSD, DASS-21, DBAS-10, PSAS-C, PSQI and ISI scales.
Statistical analysis
SPSS-21 IBM statistical package was used for statistical analysis. Cronbach’s Alpha and mean inter-item correlation coefficients were computed for GSES to assess internal consistency. Given the number of correlations and comparisons, the p-values were adjusted based to Bonferroni procedure: an initial α of .05 was divided by the number of measures shown in Table 1. The factor structure of the GSES was evaluated by explanatory factor analysis (EFA) in the clinical group.
A confirmatory factor analysis using LISREL, version 8.72 (42) was used to examine the one-factor structure of the GSES (19) in the non-clinical group. Confirmatory factor analysis offers a variety of statistical tests and indices designed to assess the goodness-of-fit of identified models (43-45). For this purpose, in the present study, the goodness-of-fit was evaluated using the following statistics: the goodness-of-fit index (GFI > .9), the adjusted goodness-of-fit index (AGFI > .90), the non-normal fit index (NNFI > .90), the comparative fit index (CFI > .90), the root mean square residual (RMSR < .08), the normal chi-square (3 > χ2/df < 2), the root mean square error of approximation (RMSEA) and its 90% confidence interval (< .05) (43-45).
To evaluate convergent validity, the correlation coefficient between GSES and DBAS-10, PSAS- C, DASS-21, ISI and PSQI were investigated. For the purpose of test-retest analysis, Pearson correlation coefficients were calculated in a subsample who was selected randomly from the clinical sample (n = 50) and completed the GSES twice with a 4 week time interval.