Chronic insomnia may contribute to the development and exacerbation of heart failure (HF), incident mortality and contributes to common and disabling symptoms (fatigue, dyspnea, anxiety, depression, excessive daytime sleepiness, and pain) and decrements in objective and subjective functional performance. The purposes of the study are to evaluate the sustained effects of CBT-I on insomnia severity, sleep characteristics, daytime symptoms, and functional performance over twelve months among patients who have stable chronic HF and chronic insomnia. The effects of the treatment on outcomes of HF (hospitalization, death) and costs of the treatment will also be examined. A total of 200 participants will be randomized to 4 bi-weekly group sessions of cognitive behavioral therapy for CBT-I (behavioral was to improve insomnia and sleep) or HF self-management education. Participants will complete wrist actigraph (wrist-watch like accelerometer) measures of sleep, diaries, reaction time, and 6 minute walk test distance. They will also complete self-report measures of insomnia, sleep, symptoms, and functional performance. In addition the effects on symptoms and function over a period of one year.
Almost 75% of HF patients, a group of about 5.1 million Americans who have poor function and high levels of morbidity and mortality, report poor sleep. As many as 25-56% of HF patients report chronic insomnia (difficulty initiating or maintaining sleep or waking early in the morning, with non-restorative sleep that persists for at least a month). Chronic insomnia may contribute to the development and exacerbation of HF and incident mortality. It is also associated with common and disabling symptoms (fatigue, dyspnea, anxiety, depression, excessive daytime sleepiness, and pain) and decrements in objective and subjective functional performance.However, insomnia is under-diagnosed and under-treated in this population. Cognitive behavioral therapy for insomnia (CBT-I) is a multi-modal behavioral treatment focused on modifying beliefs and attitudes about sleep and is efficacious in many populations. The purposes of RCT are to evaluate the sustained effects of CBT-I, compared with HF self-management education (attention control), on insomnia severity, sleep characteristics, daytime symptoms, and functional performance over twelve months among patients who have stable chronic HF and chronic insomnia and receive evidence-based HF disease management. We will also evaluate the cost-effectiveness of CBT-I compared with the attention-control condition and explore the effects of CBT-I on event-free survival. We will address the following specific aims (\*primary outcomes): (1) Test the sustained effects (baseline - 2 weeks, 6, 9, 12 months) of CBT-I provided in 4 group sessions over 8 weeks, compared with HF self-management education (attention control condition), on: (1a) \*insomnia severity and self-reported and actigraph-recorded sleep characteristics (\*sleep quality, \*sleep efficiency, sleep latency, and duration); (1b) symptoms (\*fatigue, anxiety, depression, pain, sleepiness, sleep-related impairment), and psychomotor vigilance (PVT); and (1c) symptom clusters \[membership in clusters characterized by severity of specific symptoms; transition between clusters over time\]; (2) Test the sustained effects of CBT-I on self-reported and objective functional performance; and (3) Examine the cost-effectiveness of CBT-I. Exploratory aim: We will explore the effects of CBT-I on event-free survival. A total of 200 patients will be randomized to 4 bi-weekly sessions of group CBT-I or an attention control condition consisting of HF self-management education. Wrist actigraph measures of sleep, diaries, psychomotor vigilance and 6 minute walk test distance, and self-report measures of insomnia, sleep, symptoms, and functional performance will be obtained at baseline and follow-up. Data analysis will consist of mixed effects models, latent transition analysis, stochastic cost-effectiveness analysis, and survival analysis.
Study Type
INTERVENTIONAL
Allocation
RANDOMIZED
Purpose
TREATMENT
Masking
NONE
Enrollment
195
This behavioral intervention includes strategies for modifying thoughts, cognitions and behaviors regarding sleep provided by a therapist in a group format.
This is an educational education designed to teach patients about self-management their heart failure. It includes information on medications, lifestyle, cardiac devices, diet, and when to seek assistance from a health care provider.
Yale University School of Nursing
West Haven, Connecticut, United States
Change in Insomnia Severity
Insomnia severity will be measured with the Insomnia Severity Index, a brief self-report instrument measuring patients' perception of their insomnia. The instrument includes 7 items assessing the severity of sleep onset and sleep maintenance difficulties, satisfaction with current sleep pattern, interference with daily functioning, noticeability of impairment attributed to the sleep problem, and degree of distress or concern caused by the sleep problem. Each item is rated on a 0-4 scale (4 indicates greater severity) with a total score ranging from 0 to 28. Scores are categorized as not clinically significant, sub-threshold insomnia, moderate insomnia or severe insomnia. For clarification, when results were entered, the outcome measure title was edited to include "change in" and the time frame was changed to Baseline to 3 months. When registered, the original time frame did not accurately portray the amount of time in which follow up data were collected.
Time frame: Baseline to 3 months
Change in Fatigue
The symptom of fatigue was measured with the PROMIS Item Bank v1.0 - Fatigue - Short Form 8a. The instrument measures a range of symptoms of fatigue from mild tiredness to exhaustion that may interfere with the performance of daily activities. The instrument uses a 7-day time frame and a 5-point rating scale that ranges from 1 ("Not at all") to 5 ("Very much"). The measure uses a T-score metric in which 50 is the mean of a relevant reference population (the general population) and 10 is the standard deviation (SD) of the population. Higher scores mean more fatigue. To find the total raw score we summed the values of the response to each question. The lowest possible raw score is 8; the highest possible raw score is 40. We used the score conversion table to translate the total raw score into a T-score for each participant. The T-scores are interpreted as follows: Less than 55 = None to slight 55.0-59.9 = Mild 60.0-69.9 = Moderate 70 and over = Severe. The range of scores is 33-78.
Time frame: Baseline to 3 months
Change in Sleep Efficiency-measured With PSQI
Sleep efficiency refers the ratio of time spent asleep to the amount of time spent in bed. Sleep efficiency will be subjectively measured with the Pittsburgh Sleep Quality Index, an instrument used to calculate self-reported sleep duration, sleep efficiency sleep latency, sleep disturbances, and global sleep quality. Items 1 (bed time), 3 (wake time) are used to determine time-in-bed (the difference between Q1 and Q3). Q4 is time asleep while in bed. Sleep efficiency= (time asleep/time in bed) \* 100 For clarification, when results were entered, the outcome measure title was edited to include "change in" and the time frame was changed to Baseline to 3 months. When registered, the original time frame did not accurately portray the amount of time in which follow up data were collected.
Time frame: Baseline to 3 months
Change in Sleep Quality
Sleep Quality was subjectively measured with the Pittsburgh Sleep Quality Index, an instrument used to calculate self-reported sleep duration, sleep efficiency sleep latency, sleep disturbances, and global sleep quality. The 19 self-rated items are calculated to provide a global score of sleep quality ranging from 0-21, with "0" indicating no difficulty, and "21" indicating severe difficulty in all areas. For clarification, when results were entered, the outcome measure title was edited to include "change in" and the time frame was changed to Baseline to 3 months. When registered, the original time frame did not accurately portray the amount of time in which follow up data were collected.
Time frame: Baseline to 3 months
Change in Sleep Efficiency-measured With Actigraphy
Sleep efficiency refers the ratio of time spent asleep to the amount of time spent in bed. Sleep efficiency was objectively measured using actigraphy, a method of inferring sleep from the presence or absence of wrist movement. Participants wore the Respironics Minimitter Actiwatch AW2, a wrist-worn actigraph, to elicit objective sleep efficiency for a two week period. Participants also completed a daily diary (lights out/on, times/purpose of removal, hypnotic use) for use in interpretation of actigraphy data. Sleep efficiency=(time asleep/time in bed) \* 100 For clarification, when results were entered, the outcome measure title was edited to include "change in" and the time frame was changed to Baseline to 3 months. When registered, the original time frame did not accurately portray the amount of time in which follow up data were collected.
Time frame: Baseline to 3 months
Change From Baseline in Fatigue
The symptom of fatigue was measured with the PROMIS Item Bank v1.0 - Fatigue - Short Form 8a. The instrument measures a range of symptoms of fatigue from mild tiredness to exhaustion that may interfere with the performance of daily activities. The instrument uses a 7-day time frame and a 5-point rating scale that ranges from 1 ("Not at all") to 5 ("Very much"). The measure uses a T-score metric in which 50 is the mean of a relevant reference population (the general population) and 10 is the standard deviation (SD) of the population. Higher scores mean more fatigue. To find the total raw score we summed the values of the response to each question. The lowest possible raw score is 8; the highest possible raw score is 40. We used the score conversion table to translate the total raw score into a T-score for each participant. The T-scores are interpreted as follows: Less than 55 = None to slight 55.0-59.9 = Mild 60.0-69.9 = Moderate 70 and over = Severe. The range of scores is 33-78.
Time frame: Baseline to 6 months and 12 months
Change From Baseline in Insomnia Severity
Insomnia severity will be measured with the Insomnia Severity Index, a brief self-report instrument measuring patients' perception of their insomnia. The instrument includes 7 items assessing the severity of sleep onset and sleep maintenance difficulties, satisfaction with current sleep pattern, interference with daily functioning, noticeability of impairment attributed to the sleep problem, and degree of distress or concern caused by the sleep problem. Each item is rated on a 0-4 scale (4 indicates greater severity) with a total score ranging from 0 to 28. Scores are categorized as not clinically significant, sub-threshold insomnia, moderate insomnia or severe insomnia. For clarification, when results were entered, the outcome measure title was edited to include "change in" and the time frame was changed to Baseline to 6 and 12 months. When registered, the original time frame did not accurately portray the amount of time in which follow up data were collected.
Time frame: Baseline to 6 months and 12 months
Change From Baseline in Sleep Quality
Sleep Quality was subjectively measured with the Pittsburgh Sleep Quality Index, an instrument used to calculate self-reported sleep duration, sleep efficiency sleep latency, sleep disturbances, and global sleep quality. The 19 self-rated items are calculated to provide a global score ranging from 0-21, with "0" indicating no difficulty, and "21" indicating severe difficulty in all areas. For clarification, when results were entered, the outcome measure title was edited to include "change in" and the time frame was changed to Baseline to 6 and 12 months. When registered, the original time frame did not accurately portray the amount of time in which follow up data were collected.
Time frame: Baseline to 6 months and 12 months
Change From Baseline in Sleep Efficiency Measured With PSQI (%)
Sleep efficiency refers the ratio of time spent asleep to the amount of time spent in bed. Sleep efficiency will be subjectively measured with the Pittsburgh Sleep Quality Index, an instrument used to calculate self-reported sleep duration, sleep efficiency sleep latency, sleep disturbances, and global sleep quality. Items 1 (bed time), 3 (wake time) are used to determine time-in-bed (the difference between Q1 and Q3). Q4 is time asleep while in bed. Sleep efficiency= (time asleep/time in bed) \* 100 For clarification, when results were entered, the outcome measure title was edited to include "change in" and the time frame was changed to Baseline to 6 and 12 months. When registered, the original time frame did not accurately portray the amount of time in which follow up data were collected.
Time frame: Baseline to 6 months to 12 months
Change From Baseline in Sleep Efficiency Measured With Actigraphy
Sleep efficiency refers the ratio of time spent asleep to the amount of time spent in bed. Sleep efficiency was objectively measured using actigraphy, a method of inferring sleep from the presence or absence of wrist movement. Participants wore the Respironics Minimitter Actiwatch AW2, a wrist-worn actigraph, to elicit objective sleep efficiency for a two week period. Participants also completed a daily diary (lights out/on, times/purpose of removal, hypnotic use) for use in interpretation of actigraphy data. Sleep efficiency=(time asleep/time in bed) \* 100 For clarification, when results were entered, the outcome measure title was edited to include "change in" and the time frame was changed to Baseline to 6 and 12 months. When registered, the original time frame did not accurately portray the amount of time in which follow up data were collected.
Time frame: Baseline to 6 months and 12 months
Change in Sleep Duration
Sleep duration was objectively measured using actigraphy, a method of inferring sleep from the presence or absence of wrist movement. Participants will wear the Respironics Minimitter Actiwatch AW2, a wrist-worn actigraph, to elicit objective sleep duration for a two week period. Participants will also complete a daily diary (lights out/on, times/purpose of removal, hypnotic use) for use in interpretation of actigraphy data. For clarification, when results were entered, the outcome measure title was edited to include "change in" and the time frame was changed to Baseline to 3 months. When registered, the original time frame did not accurately portray the amount of time in which follow up data were collected.
Time frame: Baseline to 3 months
Change From Baseline in Sleep Duration
Sleep duration was objectively measured using actigraphy, a method of inferring sleep from the presence or absence of wrist movement. Participants wore the Respironics Minimitter Actiwatch AW2, a wrist-worn actigraph, to elicit objective sleep duration for a two week period. Participants completed a daily diary (lights out/on, times/purpose of removal, hypnotic use) for use in interpretation of actigraphy data. For clarification, when results were entered, the outcome measure title was edited to include "change in" and the time frame was changed to Baseline to 6 and 12 months. When registered, the original time frame did not accurately portray the amount of time in which follow up data were collected.
Time frame: Baseline to 6 months and 12 months
Change in Anxiety Symptoms
Anxiety symptoms were measured with the PROMIS - Anxiety V1.- Short Form 8a. The instrument measures fear (worry, panic), anxious misery (e.g., dread), hyperarousal (e.g., tension, restlessness), and somatic symptoms (e.g., dizziness). The instrument uses a 7-day time frame and a 5-point rating scale that ranges from 1 ("Never") to 5 ("Always"). The measure uses a T-score metric in which 50 is the mean of a relevant reference population (the general population) and 10 is the standard deviation (SD) of the population. Higher scores mean more anxiety symptoms. To find the total raw score we summed the values of the response to each question. The lowest possible raw score is 8; the highest possible raw score is 40. We used the score conversion table to translate the total raw score into a T-score for each participant. The T-scores are interpreted as follows: Less than 55 = None to slight 55.0-59.9 = Mild 60.0-69.9 = Moderate 70 and over = Severe. The range of scores is 37-84.
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Time frame: Baseline to 3 months
Change From Baseline in Anxiety Symptoms
Anxiety symptoms were measured with the PROMIS - Anxiety V1.- Short Form 8a. The instrument measures fear (worry, panic), anxious misery (e.g., dread), hyperarousal (e.g., tension, restlessness), and somatic symptoms (e.g., dizziness). The instrument uses a 7-day time frame and a 5-point rating scale that ranges from 1 ("Never") to 5 ("Always"). The measure uses a T-score metric in which 50 is the mean of a relevant reference population (the general population) and 10 is the standard deviation (SD) of the population. Higher scores mean more anxiety symptoms. To find the total raw score we summed the values of the response to each question. The lowest possible raw score is 8; the highest possible raw score is 40. We used the score conversion table to translate the total raw score into a T-score for each participant. The T-scores are interpreted as follows: Less than 55 = None to slight 55.0-59.9 = Mild 60.0-69.9 = Moderate 70 and over = Severe. The range of scores is 37-84.
Time frame: Baseline to 6 months and 12 months
Change in Depressive Symptoms
Depressive symptoms were measured with the PROMIS - Depression V1.- Short Form 8a. The instrument measures negative mood (sadness), views of self (worthlessness), and social cognition (loneliness), and decreased positive affect and engagement. The instrument uses a 7-day time frame and a 5-point rating scale that ranges from 1 ("Never") to 5 ("Always"). The measure uses a T-score metric in which 50 is the mean of a relevant reference population (the general population) and 10 is the standard deviation (SD) of the population. Higher scores mean more depressive symptoms. To find the total raw score we summed the values of the response to each question. The lowest possible raw score is 8; the highest possible raw score is 40. We used the score conversion table to translate the total raw score into a T-score for each participant. The T-scores are interpreted as follows: Less than 55 = None to slight 55.0-59.9 = Mild 60.0-69.9 = Moderate 70 and over = Severe. The range of scores is 38-82.
Time frame: Baseline to 3 months
Change From Baseline in Depressive Symptoms
Depressive symptoms were measured with the PROMIS - Depression V1.- Short Form 8a. The instrument measures negative mood (sadness), views of self (worthlessness), and social cognition (loneliness), and decreased positive affect and engagement. The instrument uses a 7-day time frame and a 5-point rating scale that ranges from 1 ("Never") to 5 ("Always"). The measure uses a T-score metric in which 50 is the mean of a relevant reference population (the general population) and 10 is the standard deviation (SD) of the population. Higher scores mean more depressive symptoms. To find the total raw score we summed the values of the response to each question. The lowest possible raw score is 8; the highest possible raw score is 40. We used the score conversion table to translate the total raw score into a T-score for each participant. The T-scores are interpreted as follows: Less than 55 = None to slight 55.0-59.9 = Mild 60.0-69.9 = Moderate 70 and over = Severe. The range of scores is 38-82.
Time frame: Baseline to 6 months and 12 months
Change in Sleepiness
Sleepiness was measured using the Epworth Sleepiness Scale (ESS). The ESS is an 8-item self report instrument used to measure general levels of daytime sleepiness or sleep propensity in adults. The instrument asks subjects to rate on a scale of 0 to 3 the chances that he or she would doze in each of eight different situations. ESS scores can range from 0 to 24, with higher scores indicating higher levels of daytime sleepiness. For clarification, when results were entered, the outcome measure title was edited to include "change in" and the time frame was changed to Baseline to 3 months. When registered, the original time frame did not accurately portray the amount of time in which follow up data were collected.
Time frame: Baseline to 3 months
Change From Baseline in Sleepiness
Sleepiness will be measured using the Epworth Sleepiness Scale (ESS). The ESS is an 8-item self report instrument used to measure general levels of daytime sleepiness or sleep propensity in adults. The instrument asks subjects to rate on a scale of 0 to 3 the chances that he or she would doze in each of eight different situations. ESS scores can range from 0 to 24, with higher scores indicating higher levels of daytime sleepiness. For clarification, when results were entered, the outcome measure title was edited to include "change in" and the time frame was changed to Baseline to 6 and 12 months. When registered, the original time frame did not accurately portray the amount of time in which follow up data were collected.
Time frame: Baseline to 6 months and 12 months
Change in Dyspnea
Symptoms of dyspnea were measured with the Multidimensional Assessment of Dyspnea Scale, a 16-item instrument to measure self-reported shortness of breath and the effect of shortness of breath on daily activities. The items are used to calculate a global dyspnea index, with higher scores indicating more severe dyspnea and greater impact on activities of daily living. The range of possible scores are between 4 and 50. To calculate the Global Dyspnea Index (GDI), we converted item 15 to a 0 - 10 scale by multiplying each score by 2.5 and then finding the sum of items 1, 2, and 3, and average 4 - 14. We did not assign a score to items 4 - 14 if the respondent gave a response of "do not do activity." If a respondent selected "no shortness of breath" on item 1, we assigned a zero to items 2 - 16. Item 16 is not included in the GDI.
Time frame: Baseline to 3 months
Change From Baseline in Dyspnea
Symptoms of dyspnea were measured with the Multidimensional Assessment of Dyspnea Scale, a 16-item instrument to measure self-reported shortness of breath and the effect of shortness of breath on daily activities. The items are used to calculate a global dyspnea index, with higher scores indicating more severe dyspnea and greater impact on activities of daily living. The range of possible scores are between 4 and 50. To calculate the Global Dyspnea Index (GDI), we converted item 15 to a 0 - 10 scale by multiplying each score by 2.5 and then finding the sum of items 1, 2, and 3, and average 4 - 14. We did not assign a score to items 4 - 14 if the respondent gave a response of "do not do activity." If a respondent selected "no shortness of breath" on item 1, we assigned a zero to items 2 - 16. Item 16 is not included in the GDI.
Time frame: Baseline to 6 months and 12 months
Change in Psychomotor Vigilance
Psychomotor vigilance will be measured with the Psychomotor Vigilance Test (PVT), a widely used measure of behavioral alertness that is highly sensitive to changes related to sleep deprivation. The 10-minute PVT measures sustained or vigilant attention by recording response times to visual (or auditory) stimuli that occur at random inter-stimulus intervals. Scoring includes a numerical measure of sleepiness by counting the number of lapses in attention of the tested subject.
Time frame: Baseline to 3 months
Change From Baseline in Psychomotor Vigilance
Psychomotor vigilance will be measured with the Psychomotor Vigilance Test (PVT), a widely used measure of behavioral alertness that is highly sensitive to changes related to sleep deprivation. The 10-minute PVT measures sustained or vigilant attention by recording response times to visual (or auditory) stimuli that occur at random inter-stimulus intervals. Scoring includes a numerical measure of sleepiness by counting the number of lapses in attention of the tested subject.
Time frame: Baseline to 6 months and 12 months
Change in Functional Performance
Functional performance was measured with the Medical Outcomes Study (MOS) SF36v2 Physical Functioning Scale. The SF36v2 is a multi-purpose self-reported health survey that yields an 8-scale profile of functional health and well-being. The physical functioning scale assesses performance of daily activities, with the lowest score indicating an individual who is very limited in performing all physical activities, including bathing or dressing, and the highest score indicating an individual who can perform all types of vigorous physical activity without limitations due to health. Physical functioning scores were calculated using the Quality Metric Outcomes TM Scoring Software 4.5, which uses norm-based scoring. The range of possible scores is from 0-100; the typical range of norm based physical functioning is 20 to 60.
Time frame: Baseline to 3 months
Change From Baseline in Functional Performance
Functional performance was measured with the Medical Outcomes Study (MOS) SF36v2 Physical Functioning Scale. The SF36v2 is a multi-purpose self-reported health survey that yields an 8-scale profile of functional health and well-being. The physical functioning scale assesses performance of daily activities, with the lowest score indicating an individual who is very limited in performing all physical activities, including bathing or dressing, and the highest score indicating an individual who can perform all types of vigorous physical activity without limitations due to health. Physical functioning scores were calculated using the Quality Metric Outcomes TM Scoring Software 4.5, which uses norm-based scoring. The range of possible scores is from 0-100; the typical range of norm based physical functioning is 20 to 60.
Time frame: Baseline to 6 months and 12 months
Change in Distance (Feet) Traveled During Six Minute Walk Test
Functional capacity was objectively measured using the Six Minute Walk Test, which measures the distance that an individual can quickly walk on a flat, hard surface in a period of 6 minutes. The test is self-paced, and evaluates the global and integrated responses of all physiological systems involved during exercise. Participants choose their own intensity of exercise and are allowed to stop and rest during the test. Results are reported as an absolute value (distance walked), and interpreted according to change in functional capacity over time. For clarification, when results were entered, the outcome measure title was edited to include "change in" and the time frame was changed to Baseline to 3 months. When registered, the original time frame did not accurately portray the amount of time in which follow up data were collected.
Time frame: Baseline to 3 months
Change in Distance (Feet) Traveled During Six Minute Walk Test
Functional capacity was objectively measured using the Six Minute Walk Test, which measures the distance that an individual can quickly walk on a flat, hard surface in a period of 6 minutes. The test is self-paced, and evaluates the global and integrated responses of all physiological systems involved during exercise. Participants choose their own intensity of exercise and are allowed to stop and rest during the test. Results are reported as an absolute value (distance walked), and interpreted according to change in functional capacity over time.
Time frame: Baseline to 6 months and 12 months
Cost Effectiveness
Cost effectiveness was evaluated in terms of direct costs for health care resources used (ED visits, hospitalizations, inpatient and outpatient visits), as well as indirect costs (time missed from work, travel, and self-management and CBT-I activities). Out-of-pocket expenses were estimated using self-reported medical history health care resource use data (e.g., visits to health care providers, hospitalizations, emergency department visits). Information on costs were obtained by self-report and validated through the EMR, hospital cost accounting database, and the Medicare fee schedule.
Time frame: 12 months post treatment
Change From Baseline in Sleep Latency (Minutes)
Sleep latency is the time it takes to fall asleep after turning the lights out.
Time frame: Baseline to 6 months and 12 months
Change in Sleep Latency
Sleep latency is the amount of time it takes to fall asleep after turning off the lights.
Time frame: Baseline to 3 months
Change in Sleep Related Impairment
We used the 8-item PROMIS Sleep-Related Impairment questionnaire to measure self-reported alertness, sleepiness, tiredness, and functional impairments associated with sleep problems. The instrument uses a 7-day time frame and a 5-point rating scale that ranges from 1 ("Not at all") to 5 ("Very much"). The measure uses a T-score metric in which 50 is the mean of a relevant reference population (the general population) and 10 is the standard deviation (SD) of the population. Higher scores mean more sleep related impairment. To find the total raw score we summed the values of the response to each question. The lowest possible raw score is 8; the highest possible raw score is 40. We used the score conversion table to translate the total raw score into a T-score for each participant. The T-scores are interpreted as follows: Less than 55 = None to slight 55.0-59.9 = Mild 60.0-69.9 = Moderate 70 and over = Severe.
Time frame: Baseline to 3 months
Change From Baseline in Sleep Related Impairment
We used the 8-item PROMIS Sleep-Related Impairment questionnaire to measure self-reported alertness, sleepiness, tiredness, and functional impairments associated with sleep problems. The instrument uses a 7-day time frame and a 5-point rating scale that ranges from 1 ("Not at all") to 5 ("Very much"). The measure uses a T-score metric in which 50 is the mean of a relevant reference population (the general population) and 10 is the standard deviation (SD) of the population. Higher scores mean more sleep related impairment. To find the total raw score we summed the values of the response to each question. The lowest possible raw score is 8; the highest possible raw score is 40. We used the score conversion table to translate the total raw score into a T-score for each participant. The T-scores are interpreted as follows: Less than 55 = None to slight 55.0-59.9 = Mild 60.0-69.9 = Moderate 70 and over = Severe.
Time frame: Baseline to 6 months and 12 months