Participants and Materials
The procedures and interventions for this project were described in a published protocol report [25]. This intervention trial was described according to the CONSORT 2010 guidelines [26]. Prior to being enrolled in the study, potential participants were screened according to eligibility criteria, which are presented in Table 1.
Study Design
This RCT had an allocation ratio of 1:1 and utilized a superiority framework to test the effectiveness of the CBT-I. Participants were randomly assigned to either the CBT-I group (n=14) or the HE group (n=14). We used age to stratify participants into either the older (63-75 years) or the younger (40-62 years) age group. This study was registered in the Clinical Trials Registry (NCT03713996) [27]. This study was approved by the Institutional Review Board and the Human Subjects Committee of the University of Kansas Medical Center. All participants signed a written informed consent before the assessment visit. Data collections and provided interventions took place at the University of Kansas Medical Center.
Outcomes
All participants completed outcome measures at the baseline, and all participants completed the same outcome measures one week after completing the intervention. The primary outcome, insomnia severity, was included in the RCT Part I in which the power calculation was established and its preliminary data were published elsewhere [24].
Diabetes control measurement: A point-of-care instrument was used to assess HbA1c using a disposable finger stick HbA1c kit (A1CNow+ test kit; Bayer Healthcare, Tarrytown, NY). This instrument measures the level of glycosylated hemoglobin via an immunoassay test, and reflects the average glucose blood levels over the period of 6 to 12 weeks [28]. During a previous diabetes management program, the A1CNow+ provided accuracy and precision when performing a point-of-care, and a 0.05 reduction in HbA1c is considered clinically meaningful [29]. In addition, random blood glucose (RBG) levels were assessed by a glucose meter (FreeStyle Flash, Contour® Bayer Healthcare, Diagnostic Division, Tarrytown, NY). Participants were tested for the RBG without time specifications or diet instructions. During the intervention, participants in the CBT-I group were asked to record their own blood glucose levels right before bedtime and after first awakening in the morning throughout the study period (i.e., 7 days/nights per week for 7 weeks).
Diabetes self-care behavior (DSCB): Self-care was assessed using the Diabetes Care Profile (DCP), which is a validated survey that measures 13 psychosocial and educational factors [30, 31]. The 13 domains that are associated with the management of diabetes, are inclusive of the following: understanding the management of practice, support, control problems, social and personal factors, positive attitude, negative attitude, care ability, importance of care, self-care adherence, diet adherence, long-term care benefits, exercise barriers, and glucose monitoring barriers [31]. A standardized total DCP composite score was established to present all 13 domains that were scored according to the Fitzgerald et al. scoring criteria [31]. Next, each participant’s domain score was standardized using z-scores, and then averaged to create a standardized total DCP composite score. High scores on the DCP composite score indicate better DSCB.
Fatigue severity: Daily fatigue was measured using the Fatigue Severity Scale (FSS) that consists of 9 items developed to assess disabling fatigue on daily life. The FSS has been shown to be valid and reliable [32]. Each item was measured on a 7-point Likert scale ranging from 1 (strongly disagree) to 7 (strongly agree). Mean item response for the completed FSS items was used for analysis.
Interventions
All participants in the CBT-I group and HE group attended 6 sessions that were scheduled consistently one session per week with the CBT-I provider. These sessions were provided for around 45 minutes for both groups to assure all participants received the same amount of attention. Neither the CBT-I provider nor the participants were blinded in this study. The protocol paper describes session by session of both interventions [33].
Cognitive Behavioral Therapy for Insomnia: This protocol intervention was designed based on a session-by-session guide [34]. Five main therapeutic techniques were provided during the 6-sessions including sleep restriction therapy, stimulus control therapy, sleep hygiene, relaxation techniques, and cognitive therapy. In order to monitor nightly sleep changes and issues, the CBT-I provider reviewed the sleep diary for each session. In addition, calculations in sleep changes were made to prescribe the sleep schedules for the following week. The calculations in the sleep changes were made based on the sleep efficiency (the ratio of total sleep time and total bedtime multiplied by 100) from the weekly sleep diary. At each session, the time spent in bed and out of bed was prescribed based on the calculation of sleep efficiency in percentages. If the sleep efficiency was greater than 90%, the opportunity to go to bed earlier was extended by 15 minutes. If the sleep efficiency was between 85 and 89.9%, the same sleep schedule was prescribed, and if it was less than 85%, then bedtime moved 15 minutes later.
Session 1: Sleep restriction therapy, stimulus control therapy and sleep hygiene were provided. Sleep restriction therapy aligns the time in bed with the total sleep time by identifying the wake time and total sleep time needed to increase the sleep efficiency [35, 36]. Stimulus control associates the bed environment to sleep only (or sex) to reinforce the circadian rhythm [35, 36]. In addition, sleep hygiene minimizes the influence of negative behaviors on sleep quality and quantity. The principles of sleep hygiene were provided including the impact of diet, exercise, caffeine, alcohol, and environment on the quality of sleep [35, 36].
Session 2: Calculating sleep efficiency, reviewing the principles of sleep hygiene, and providing the diaphragmatic breathing technique were covered in this session. During this week, we also reviewed the sleep diary to confirm any necessary sleep changes (i.e., adjustments to the time both in and out of bed.) The diaphragmatic breathing technique promotes muscle relaxation, better breathing performance, and memory relaxation [37]. It also was especially emphasized for those who were not able to relax.
Session 3: Calculating both sleep efficiency and mindfulness were conducted during this session. Mindfulness reduces cognitive and somatic arousal for people with insomnia who received CBT-I [38]. The principles of mindfulness including how to be non-judgmental and incorporate patience, trust, acceptance, and letting go were covered in this session.
Session 4: Calculating sleep efficiency and progressive muscle relaxation were reviewed in this session. Muscle relaxation therapy helped in improving insomnia and depression symptoms when used in CBT-I [39]. Muscle relaxation therapy is a physiological intervention aimed to assess and decrease muscle tension [39].
Session 5: Calculating sleep efficiency and cognitive therapy were done in this session. Cognitive therapy changes both detrimental beliefs and attitudes about sleep. During this session, we worked on reducing the participants’ sleep efforts, catastrophizing, and their anxiety about sleep, while also working on their willingness to modify their sleep-related behaviors and engage in good sleep strategies.
Session 6: Assessing treatment benefits and insomnia relapse education were provided in this session. We graphically reviewed the sleep efficiency of each session to show the sleep changes during the six sessions of CBT-I. In addition, we discussed the approaches to maintain clinical gains and how to remedy any incidents when insomnia returns.
Health Education: Five main health education materials were introduced during the six sessions including brief sleep hygiene, foot care, diabetes classifications, healthy diet, and physical activity. During the HE sessions, we provided informal face to face interviews to better engage the participants in the conversations. Participants’ comprehension of and experiences about the provided materials were facilitated through open questions. Details of the provided sessions for the HE group were provided in the protocol paper of this study [33].
Statistical Analysis
All data analyses were performed using SPSS 23.0 for Mac (Chicago, IL) and R (https://www.R-project.org/) [40]. Descriptive statistics included means and standard deviations for the assessed variables at the baseline (14 participants) and at the post-assessment (13 participants). We used Shapiro–Wilk tests to assess the normality of residuals during model development. For the main analysis, we used Mann-Whitney U tests to examine the between-group differences of the CBT-I and HE groups in HbA1c, RBG, DSCB, and fatigue mean change scores for those who completed the study. We also used Wilcoxon signed-rank tests to compare the within-group changes for both groups. Effect sizes were calculated using Cohen’s d [41]. For graphical purposes, we calculated absolute percentage changes in all outcomes to graph the between-group differences. For secondary purpose, we used linear regression analyses to predict blood glucose levels (before bedtime and after first awakening in the morning) based on 49 days throughout the course of the study, including 6 weeks CBT-I and post-assessment. For all analyses, the alpha level was set at .05.