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CompletedNCT03968900Updated Aug 25, 2026Results posted

Racial Differences in Circadian and Sleep Mechanisms for Nicotine Dependence, Craving, and Withdrawal

An interventional study of Sleep restriction condition and Sleep extension condition in Smoking, Sleep Disturbance and Nicotine Dependence, sponsored by University of Alabama at Birmingham. Completed at 1 site in United States. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-08-25.

Sponsored by University of Alabama at Birmingham · Not applicable, Interventional, and Treatment

Phase
Not applicable
Study type
Interventional
Enrollment
29
Allocation
Randomized
Ages
18 Years and older
Sex
All
01

Study summary

The number one preventable cause of death in the world is tobacco use. Cigarette smoking in particular, costs an estimated $300 billion due to expenses related to medical care and lost productivity. Despite similar smoking prevalence rates, blacks suffer disproportionately from smoking-related harms compared to whites.Sleep disparities such as shortened sleep duration, shorter circadian periodicity, earlier chronotype, and increased variability of sleep timing have been reported more frequently in blacks compared to whites. Given that poor sleep quality predicts relapse from smoking cessation programs, particularly among socioeconomically disadvantaged adults, sleep deficiencies and irregular timing of sleep may impact smoking craving and withdrawal symptoms over the course of the 24-hour day. Surprisingly, few studies have examined these temporal patterns of smoking and craving, and none with regard to sleep disruption, chronotype or racial disparities. A better understanding of these factors may explain heterogeneity within the smoking population, especially in minorities. Thus, the purpose of this proposal is to test the central hypothesis that the impact of chronotype and impaired sleep on cigarette usage as well as smoking dependence, urge/craving, and withdrawal depends on race.

Read the detailed description

Three specific aims will determine: contributions of sleep timing and sleep quality and quantity to racial disparities in smoking status (Aim 1), objective sleep characteristics and smoking behavior among blacks and whites who smoke cigarettes (Aim 2), and whether sleep restriction modifies craving and withdrawal in racially diverse smokers (Aim 3). Specifically, we will utilize self-report questionnaires, objective measures of sleep quality and timing (actigraphy) and circadian phase (dim light melatonin onset), as well as ecological momentary assessment of cigarette use, smoking urges, cravings, and withdrawal symptoms to identify circadian and sleep characteristics that are most strongly associated with smoking status, heaviness of smoking and dependence among blacks and whites. Finally, we will test whether acute sleep restriction (4 hours of time-in-bed) versus sleep extension (10 hours of time-in-bed) modifies craving and withdrawal symptoms following cessation in black and white smokers. If successful, the results of this study will result in identification of circadian dysfunction and insufficient sleep as mechanisms that underlie the association between sleep and cigarette smoking behaviors and dependence in diverse populations. Moreover, these findings are likely to inform clinicians of the importance of sleep and sleep timing on cigarette smoking behaviors and dependence that will help in the development of novel interventions to reduce morbidity and mortality caused by tobacco use.

02

Conditions studied

  • Smoking
  • Sleep Disturbance
  • Nicotine Dependence

Keywords

  • smoking
  • sleep deficiencies
  • socioeconomic disadvantage
  • Race
03

In context

Smoking

268 studies on the registry are indexed under Smoking; 136 are open to participants now.

This study's enrollment of 29 is below the median of 120 across 211 interventional studies indexed under Smoking.

Browse Smoking studies →

Lead sponsor

University of Alabama at Birmingham is the lead sponsor of 1,396 studies on the registry; 284 are open to participants now.

Of its 156 completed or terminated interventional studies of FDA-regulated products, 124 (79%) have results posted.

Counted across the registry records on this site, refreshed daily.

04

Who can participate

Ages eligible
18 Years and older
Sexes eligible
All
Accepts healthy volunteers
No

Eligibility criteria

Sub-Study 1

Inclusion Criteria:

  1. 18 years or older
  2. Able to read and speak English
  3. Non-Hispanic African American (Black) or non-Hispanic white race
  4. Daily smoker (5 or more cigarettes a day for the past one year and having smoked more than 100 cigarettes in lifetime) or non-smoker (smoked fewer than 100 cigarettes in a lifetime and no smoking-not even a puff- in the last year)

  5. Currently residing in Alabama

    Exclusion Criteria:

  6. Non-English speaking
  7. Lives in restricted environment that does not allow smoking
  8. Pregnant or lactating
  9. Daily or exclusive use of other tobacco products (e.g., cigars, e-cigarettes) if a smoker; if non-smoker, any other tobacco product use is exclusionary
  10. Currently receiving smoking cessation treatment or using electronic cigarettes or other tobacco to try and quit smoking cigarettes
  11. Participants would work outside normal 7 a.m. to 6 p.m. hours
  12. Former smokers

Sub-study 2

Inclusion Criteria:

  1. 18 years or older
  2. Able to read and speak English
  3. Non-Hispanic African American (Black) or non-Hispanic white race
  4. Daily smoker defined as smoking 5 or more cigarettes a day for the past one year and having smoked more than 100 cigarettes in lifetime, as well as by an expired Carbon Monoxide (CO )cut-off of Carbon Monoxide (CO)>10ppm and positive cotinine test to ensure daily smoking OR non-smoker defined as smoking fewer than 100 cigarettes in a lifetime and no smoking-not even a puff- in the last year, as well as by an expired Carbon monoxide (CO) cut-off of Carbon Monoxide (CO)\<3 ppm and negative cotinine test.

  5. Currently residing in Alabama

    Exclusion Criteria:

  6. Non-English speaking
  7. Lives in restricted environment that does not allow smoking
  8. Pregnant or lactating
  9. Testing positive on urine drug screen test at baseline - any drugs other than Tetrahydrocannabinol (THC) not allowed
  10. Daily or exclusive use of other tobacco products (e.g., cigars, e-cigarettes) if a smoker; if non-smoker, any other tobacco product use is exclusionary
  11. Currently receiving smoking cessation treatment or using electronic cigarettes or other tobacco to try and quit smoking cigarettes
  12. Participants would work outside normal 7 a.m. to 6 p.m. hours
  13. Former smokers
  14. History of a medical condition (e.g., bipolar disorder, migraine, or seizure disorder) that might be exacerbated by sleep deprivation as a result of Study 3
  15. History of a serious lung/breathing disease that prevents one from walking or holding their breath for 10 seconds (in order to complete Carbon Monoxide breath test)
  16. Cognitive impairment such that participant is unable to provide informed consent
  17. Acutely suicidal, manic, acutely intoxicated, or otherwise not stable enough to provide informed consent
  18. Living outside of the Birmingham metro area (> 20 miles away from University of Alabama at Birmingham Main Campus)

Sub-study 3

Inclusion Criteria:

  1. 18 years or older
  2. Able to read and speak English
  3. Non-Hispanic African American (Black) or non-Hispanic white race
  4. Daily smoker defined as smoking 5 or more cigarettes a day for the past one year and having smoked more than 100 cigarettes in lifetime, as well as by an expired Carbon Monoxide (CO) cut-off of Carbon Monoxide (CO)>10ppm and positive cotinine test to ensure daily smoking

  5. Currently residing in Alabama

    Exclusion Criteria:

  6. Non-English speaking
  7. Lives in restricted environment that does not allow smoking
  8. Pregnant or lactating
  9. Daily or exclusive use of other tobacco products (e.g., cigars, e-cigarettes) if a smoker; if non-smoker, any other tobacco product use is exclusionary
  10. Currently receiving smoking cessation treatment or using electronic cigarettes or other tobacco to try and quit smoking cigarettes
  11. Participants would work outside normal 7 a.m. to 6 p.m. hours
  12. Former smokers
  13. History of a medical condition (e.g., bipolar disorder, migraine, or seizure disorder) that might be exacerbated by sleep deprivation as a result of Study 3
  14. Currently taking any psychiatric medications, pain medications (i.e., opioids), or sleep medications (e.g., Ambien, trazodone, melatonin pills, Cannabidiol (CBD) products)
  15. History of a serious lung/breathing disease that prevents one from walking or holding their breath for 10 seconds
  16. Testing positive on urine drug screen test at baseline - any drugs other than Tetrahydrocannabinol (THC) not allowed
  17. Has an apnea-hypopnea index (AHI) score of > 15 on home sleep testing that was conducted during sub-study 2
  18. Uses Continuous positive airway pressure (CPAP) machine to sleep at night
  19. Cognitive impairment such that participant is unable to provide informed consent
  20. Acutely suicidal, manic, acutely intoxicated, or otherwise not stable enough to provide informed consent
  21. Living outside of the Birmingham metro area (> 20 miles away from University of Alabama at Birmingham Main Campus)
05

Study design

Phase
Not applicable
Primary purpose
Treatment
Allocation
Randomized
Intervention model
Crossover assignment
Masking
None (open label)
Enrollment
29 participants (actual)

Study arms

  • Experimental
    Sleep Restriction

    4 hours time in bed (1 am to 5 am)

    Behavioral: Sleep restriction condition

  • Experimental
    Sleep Extension

    10 hours time in bed (10 pm to 8 am)

    Behavioral: Sleep extension condition

Interventions

  • BehavioralSleep restriction condition

    On day 1, participants will complete study assessments and will be fitted with an Actiwatch and instructed to continue a fixed time in bed (8 hours duration with no more than 20 min deviation) centered on habitual sleep (e.g., 11:00 p.m. to 7:00 a.m.). Naps will not be allowed. Following the one-week baseline sleep stabilization, participants will engage in the sleep restriction condition (4 hours, TIB \[Time in Bed\]; 1:00 a.m. to 5:00 a.m.). On the day of each sleep study, participants will be admitted to University of Alabama Birmingham (UAB) Highlands Hospital sleep unit at 7:00 p.m. and do an initial CO breathe test and fill out study questionnaires and a timeline follow-back procedure Participants will monitored for smoking withdrawal. Every 2 hours, participants to fill out various questionnaires. Participants will repeat the same conditions as the first night. After a two-week washout, participants will be crossed over to the alternate sleep extension/restriction condition.

  • BehavioralSleep extension condition

    sleep extension On day 1, participants will complete study assessments and will be fitted with an Actiwatch and instructed to continue a fixed time in bed (8 hours duration with no more than 20 min deviation) centered on habitual sleep (e.g., 11:00 p.m. to 7:00 a.m.). Naps will not be allowed. Following the one-week baseline sleep stabilization, participants will engage in the sleep extension condition (10 hours, (TIB); 10:00 p.m. to 8:00 a.m.). On the day of each sleep study, participants will be admitted to University of Alabama Birmingham Highlands Hospital sleep unit at 7:00 p.m. and do an initial CO breathe test and fill out study questionnaires and a timeline follow-back procedure Participants will monitored for smoking withdrawal. Every 2 hours, participants to fill out various questionnaires. Participants will repeat the same conditions as the first night. After a two-week washout, participants will be crossed over to the alternate sleep extension/restriction condition.

06

What researchers measure

Primary outcomes

  1. Sleep Hygiene Index

    A 13-item scale that assesses behaviors, such as variability in wake-time, timing of physical activity, and substance use, that comprise sleep hygiene. Higher values indicate worse sleep hygiene. The minimum value is 0, and the maximum value is 52.

    Time frame: 1 day at baseline before either intervention

Secondary outcomes

  1. Pittsburgh Sleep Quality Index

    A 7-item self-report measure that assesses global sleep quality over the past month. Additionally, sub-scales that include duration of sleep, sleep disturbance, sleep latency, daytime dysfunction, sleep efficiency, and dependence on hypnotic medication may be calculated from individual items. Higher scores indicate worse sleep quality. The minimum score is 0, and the maximum score is 21.

    Time frame: 1 day at baseline before either intervention

  2. Munich Chronotype Questionnaire

    Questionnaire that determines chronotype from midsleep time calculated from sleep onset and offset on both free days and work days. Chronotype will be determined from the mid-sleep time on days off. Specifically, Mid-sleep time is equal to Sleep onset + Sleep duration/2. For those who sleep longer on days off than on workdays, we will correct for weekend recovery sleep by subtracting 'sleep debt' accumulated, which is estimated by the following equation: Sleep duration on free days - Sleep duration (average) for the week/2. Chronotype is the participant's midsleep time on free days. Higher values indicate that midsleep time is later in the day. The minimum value is 0, and the maximum value is 24.

    Time frame: 1 day at baseline before either intervention

  3. Fagerström Test for Nicotine Dependence

    A 6-item self-report measure of nicotine dependence derived from the Fagerström Tolerance Questionnaire. Higher scores indicate greater nicotine dependence. The minimum value is 1, and the maximum value is 10.

    Time frame: 1 day at baseline before either intervention

  4. Snoring History, Tired During the Day, Observed Stop Breathing While Sleep, High Blood Pressure, BMI More Than 35 kg/m2, Age More Than 50 Years, Neck Circumference More Than 40 cm and Male Gender (STOP-BANG) Questionnaire

    A 8-item self-report questionnaire that assesses the primary risk factors for obstructive sleep apnea to create a total score that ranges from 0 to 8. Higher scores indicate greater risk of sleep apnea.

    Time frame: 1 day at baseline before either intervention

  5. Insomnia Severity Index

    A 7-item self-report questionnaire that assesses the severity of core symptoms of insomnia over the previous 2 weeks. Higher scores indicate more severe insomnia. The minimum score is 0, and the maximum score is 28.

    Time frame: 1 day at baseline before either intervention

  6. Dysfunctional Beliefs and Attitudes About Sleep (DBAS)

    A 16-item questionnaire that assesses beliefs about sleep and the consequences of poor sleep. Higher scores indicate more dysfunctional beliefs about sleep. The minimum score is 0, and the maximum score is 10.

    Time frame: 1 day at baseline before either intervention

  7. Epworth Sleepiness Scale (ESS)

    A 8-item questionnaire that asks individuals to rate their "chances of dozing off" on a scale of 0 (never) to 3 (high) in eight different situations. The scores are summed to create a total score with higher values indicating higher chances of dozing off. The minimum score is 0, and the maximum score is 24.

    Time frame: 1 day at baseline before either intervention

  8. Everyday Discrimination Scale (EDS)

    This 9-item assessment queries about experiences of discrimination such as being treated less respectfully or people thinking that you are dishonest. Responses range from "almost every day" to "never." Higher score indicate more ways that discrimination was experienced. The minimum score is 0, and the maximum score is 9.

    Time frame: 1 day at baseline before either intervention

  9. Perceived Stress Scale - 10 Item (PSS-10)

    Self-report questionnaire that assesses a person's perceived stress with a 5-point Likert scale ranging from "Never" to "Very Often." Higher scores indicate greater levels of perceived stress. The minimum score is 0, and the maximum score is 40.

    Time frame: 1 day at baseline before either intervention

Other outcomes

  1. Duke- The University of North Carolina at Chapel Hill (UNC) Functional Social Support Questionnaire (FSSQ)

    A 8-item 1-5 Likert scale ranging from "much less than I would like" to "as much as I would like" that measures perceived social support. Higher scores indicate greater social support. The minimum score is 1, and the maximum score is 40.

    Time frame: 1 day at baseline before either intervention

  2. Patient Health Questionnaire (PHQ-9)

    A 9-item instrument that measures severity of depression as well as the presence of suicide ideation. Higher scores indicate more sever symptoms of depression. The minimum score is 0, and the maximum score is 27.

    Time frame: 1 day at baseline before either intervention

  3. Generalized Anxiety Disorder (GAD-7)

    A 7-item anxiety scale used to identify probable cases of generalized anxiety disorder. Higher scores indicate more severe symptoms of anxiety. The minimum score is 0, and the maximum score is 28.

    Time frame: 1 day at baseline before either intervention

  4. Assessing Smoking History

    Smoking history will be assessed for daily smokers as smoking 5 or more cigarettes a day for the past one year and having smoked more than 100 cigarettes in lifetime or non-smoker defined as smoking fewer than 100 cigarettes in a lifetime and no smoking-not even a puff- in the last year. Using those definitions, we determined the number of participants who were smokers.

    Time frame: 1 day at baseline before either intervention

  5. Brief Wisconsin Inventory of Smoking Dependence Motives (WISDM-37)

    The WISDM measures how strongly participants feel 11 potential motivations for smoking. Higher scores indicate being more strongly motivated to smoke. The minimum score is 11, and the maximum score is 77.

    Time frame: 1 day at baseline before either intervention

  6. Tobacco Craving Questionnaire-SF (TCQ-SF)

    The TCQ-SF contains 12 items to assess participants' craving to smoke cigarettes. Higher scores indicate stronger craving for tobacco. The minimum score is 12, and the maximum score is 84.

    Time frame: 1 day at baseline before either intervention

  7. Alcohol, Smoking, and Substance Involvement Screening Test (ASSIST)

    The ASSIST asks questions assessing level of dependence to 10 different substances. Higher scores indicate more negative impacts of substance use. the minimum score is 0, and the maximum score is 280.

    Time frame: 1 day at baseline before either intervention

  8. Minnesota Nicotine Withdrawal Scale (MNWS).

    The MNWS is an 8-item measure designed to assess Smokers' cigarette withdrawal in the last 24 hours. Higher scores indicate more severe symptoms of nicotine withdrawal. The minimum score is 0, and the maximum score is 32.

    Time frame: 1 day at baseline before either intervention

  9. Alcohol Use Disorders Identification Test-Consumption (AUDIT-C).

    A brief 3-item alcohol screening measure that identifies hazardous drinkers or those who have active alcohol use disorders. Higher scores indicate more symptoms of alcohol use disorder. The minimum score is 0, and the maximum score is 12.

    Time frame: 1 day at baseline before either intervention

  10. Pain, Enjoyment, General Activity (PEG) Scale

    The PEG Scale contains 3 questions regarding how much pain has interfered with enjoyment of life and general activity in the past 7 days. Higher scores indicate greater interference from pain. The minimum score is 0, and the maximum score is 10.

    Time frame: 1 day at baseline before either intervention

  11. Trauma History Scale (THS)

    The THS is a brief 14-item self-report measure designed to assess traumatic events and how much those events are emotionally bothersome. The scale counts the number of traumas endorsed. The minimum value is 0, and the maximum value is 14.

    Time frame: 1 day at baseline before either intervention

  12. PTSD Checklist-Short Form (PCL-5)

    The short form of the 20-item PCL-5 which assesses the presence and severity of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) criteria for PTSD in the past month. The short form contains 4 items. Higher scores indicate more sever symptoms of PTSD. The minimum score is 0, and the maximum score is 16.

    Time frame: 1 day at baseline before either intervention

  13. International Consultation on Incontinence Questionnaire-Overactive Bladder

    4 items pertaining to overactive bladder symptoms experienced in the past 4 weeks. Higher scores indicate more symptoms of overactive bladder. The minimum score is 0, and the maximum score is 16.

    Time frame: 1 day at baseline before either intervention

  14. International Physical Activity Questionnaire (IPAQ)

    A set of questionnaires designed to assess physical activity and sedentary lifestyles. The questionnaire measures the minutes of physical activity per week, weighted by the intensity of the activity, referred to as the MET-min. The minimum value is 0, and a value that indicates high levels of activity per week would be 3000.

    Time frame: 1 day at baseline before either intervention

  15. Standard Shiftwork Index (SSI)

    A battery of self-report questionnaires measuring shift workers' sleep and stress outcomes. We are using the physical health subsections of this questionnaire. The scale counts the number of physical conditions endorsed. The minimum score is 0, and the maximum score is 23.

    Time frame: 1 day at baseline before either intervention

  16. Fatigue Severity Scale (FSS)

    A 9-item scale measuring severity of fatigue and its effect on participants' activities and lifestyle. Higher scores indicate more severe fatigue. The minimum score is 9, and the maximum score is 63.

    Time frame: 1 day at baseline before either intervention

  17. Assessing Continuous Positive Airway Pressure (CPAP) Use

    A 5-item survey designed by the research team to assessed whether or not participants are prescribed CPAP, and their adherence to using it. Using that questionnaire, we determined the number of participants who used a CPAP.

    Time frame: 1 day at baseline before either intervention

07

Results

Posted Jul 31, 2026

Participant flow

First Sleep Condition (2 nights)
Participant flow — First Sleep Condition (2 nights)
MilestoneSleep Restriction First, Then Sleep ExtensionSleep Extension First, Then Sleep Restriction
Started1217
Completed1214
Not completed03
Withdrew: Withdrawal by subject03
Washout (14 days)
Participant flow — Washout (14 days)
MilestoneSleep Restriction First, Then Sleep ExtensionSleep Extension First, Then Sleep Restriction
Started1214
Completed1214
Not completed00
Second Sleep Condition (2 nights)
Participant flow — Second Sleep Condition (2 nights)
MilestoneSleep Restriction First, Then Sleep ExtensionSleep Extension First, Then Sleep Restriction
Started1214
Completed1114
Not completed10
Withdrew: Lost to follow-up10

Outcome measures

PrimarySleep Hygiene Index

A 13-item scale that assesses behaviors, such as variability in wake-time, timing of physical activity, and substance use, that comprise sleep hygiene. Higher values indicate worse sleep hygiene. The minimum value is 0, and the maximum value is 52.

Time frame:
1 day at baseline before either intervention
Reported as:
Mean · units on a scale
Sleep Hygiene Index
units on a scaleCompleted Sleep RestrictionCompleted Sleep Extension
Sleep Hygiene Index19.31 ± 6.4419.56 ± 6.44
SecondaryPittsburgh Sleep Quality Index

A 7-item self-report measure that assesses global sleep quality over the past month. Additionally, sub-scales that include duration of sleep, sleep disturbance, sleep latency, daytime dysfunction, sleep efficiency, and dependence on hypnotic medication may be calculated from individual items. Higher scores indicate worse sleep quality. The minimum score is 0, and the maximum score is 21.

Time frame:
1 day at baseline before either intervention
Reported as:
Mean · units on a scale
Pittsburgh Sleep Quality Index
units on a scaleCompleted Sleep RestrictionCompleted Sleep Extension
Pittsburgh Sleep Quality Index7.58 ± 6.447.76 ± 3.87
SecondaryMunich Chronotype Questionnaire

Questionnaire that determines chronotype from midsleep time calculated from sleep onset and offset on both free days and work days. Chronotype will be determined from the mid-sleep time on days off. Specifically, Mid-sleep time is equal to Sleep onset + Sleep duration/2. For those who sleep longer on days off than on workdays, we will correct for weekend recovery sleep by subtracting 'sleep debt' accumulated, which is estimated by the following equation: Sleep duration on free days - Sleep duration (average) for the week/2. Chronotype is the participant's midsleep time on free days. Higher values indicate that midsleep time is later in the day. The minimum value is 0, and the maximum value is 24.

Time frame:
1 day at baseline before either intervention
Reported as:
Mean · number of hours after midnight
Munich Chronotype Questionnaire
number of hours after midnightCompleted Sleep RestrictionCompleted Sleep Extension
Munich Chronotype Questionnaire11.49 ± 12.3811.49 ± 12.38
SecondaryFagerström Test for Nicotine Dependence

A 6-item self-report measure of nicotine dependence derived from the Fagerström Tolerance Questionnaire. Higher scores indicate greater nicotine dependence. The minimum value is 1, and the maximum value is 10.

Time frame:
1 day at baseline before either intervention
Reported as:
Mean · units on a scale
Fagerström Test for Nicotine Dependence
units on a scaleCompleted Sleep RestrictionCompleted Sleep Extension
Fagerström Test for Nicotine Dependence5.12 ± 2.015.24 ± 1.94
SecondarySnoring History, Tired During the Day, Observed Stop Breathing While Sleep, High Blood Pressure, BMI More Than 35 kg/m2, Age More Than 50 Years, Neck Circumference More Than 40 cm and Male Gender (STOP-BANG) Questionnaire

A 8-item self-report questionnaire that assesses the primary risk factors for obstructive sleep apnea to create a total score that ranges from 0 to 8. Higher scores indicate greater risk of sleep apnea.

Time frame:
1 day at baseline before either intervention
Reported as:
Mean · units on a scale
Snoring History, Tired During the Day, Observed Stop Breathing While Sleep, High Blood Pressure, BMI More Than 35 kg/m2, Age More Than 50 Years, Neck Circumference More Than 40 cm and Male Gender (STOP-BANG) Questionnaire
units on a scaleCompleted Sleep RestrictionCompleted Sleep Extension
Snoring History, Tired During the Day, Observed Stop Breathing While Sleep, High Blood Pressure, BMI More Than 35 kg/m2, Age More Than 50 Years, Neck Circumference More Than 40 cm and Male Gender (STOP-BANG) Questionnaire2.31 ± 1.442.28 ± 1.46
SecondaryInsomnia Severity Index

A 7-item self-report questionnaire that assesses the severity of core symptoms of insomnia over the previous 2 weeks. Higher scores indicate more severe insomnia. The minimum score is 0, and the maximum score is 28.

Time frame:
1 day at baseline before either intervention
Reported as:
Mean · units on a scale
Insomnia Severity Index
units on a scaleCompleted Sleep RestrictionCompleted Sleep Extension
Insomnia Severity Index12.5 ± 6.0712.56 ± 6.19
SecondaryDysfunctional Beliefs and Attitudes About Sleep (DBAS)

A 16-item questionnaire that assesses beliefs about sleep and the consequences of poor sleep. Higher scores indicate more dysfunctional beliefs about sleep. The minimum score is 0, and the maximum score is 10.

Time frame:
1 day at baseline before either intervention
Reported as:
Mean · units on a scale
Dysfunctional Beliefs and Attitudes About Sleep (DBAS)
units on a scaleCompleted Sleep RestrictionCompleted Sleep Extension
Dysfunctional Beliefs and Attitudes About Sleep (DBAS)4.77 ± 1.544.77 ± 1.54
SecondaryEpworth Sleepiness Scale (ESS)

A 8-item questionnaire that asks individuals to rate their "chances of dozing off" on a scale of 0 (never) to 3 (high) in eight different situations. The scores are summed to create a total score with higher values indicating higher chances of dozing off. The minimum score is 0, and the maximum score is 24.

Time frame:
1 day at baseline before either intervention
Reported as:
Mean · units on a scale
Epworth Sleepiness Scale (ESS)
units on a scaleCompleted Sleep RestrictionCompleted Sleep Extension
Epworth Sleepiness Scale (ESS)6.85 ± 4.566.64 ± 4.53
SecondaryEveryday Discrimination Scale (EDS)

This 9-item assessment queries about experiences of discrimination such as being treated less respectfully or people thinking that you are dishonest. Responses range from "almost every day" to "never." Higher score indicate more ways that discrimination was experienced. The minimum score is 0, and the maximum score is 9.

Time frame:
1 day at baseline before either intervention
Reported as:
Mean · units on a scale
Everyday Discrimination Scale (EDS)
units on a scaleCompleted Sleep RestrictionCompleted Sleep Extension
Everyday Discrimination Scale (EDS)2.38 ± 2.682.40 ± 2.74
SecondaryPerceived Stress Scale - 10 Item (PSS-10)

Self-report questionnaire that assesses a person's perceived stress with a 5-point Likert scale ranging from "Never" to "Very Often." Higher scores indicate greater levels of perceived stress. The minimum score is 0, and the maximum score is 40.

Time frame:
1 day at baseline before either intervention
Reported as:
Mean · units on a scale
Perceived Stress Scale - 10 Item (PSS-10)
units on a scaleCompleted Sleep RestrictionCompleted Sleep Extension
Perceived Stress Scale - 10 Item (PSS-10)15.12 ± 5.8315.20 ± 5.94
Other pre-specifiedDuke- The University of North Carolina at Chapel Hill (UNC) Functional Social Support Questionnaire (FSSQ)

A 8-item 1-5 Likert scale ranging from "much less than I would like" to "as much as I would like" that measures perceived social support. Higher scores indicate greater social support. The minimum score is 1, and the maximum score is 40.

Time frame:
1 day at baseline before either intervention
Reported as:
Mean · units on a scale
Duke- The University of North Carolina at Chapel Hill (UNC) Functional Social Support Questionnaire (FSSQ)
units on a scaleCompleted Sleep RestrictionCompleted Sleep Extension
Duke- The University of North Carolina at Chapel Hill (UNC) Functional Social Support Questionnaire (FSSQ)31.50 ± 7.4031.32 ± 7.49
Other pre-specifiedPatient Health Questionnaire (PHQ-9)

A 9-item instrument that measures severity of depression as well as the presence of suicide ideation. Higher scores indicate more sever symptoms of depression. The minimum score is 0, and the maximum score is 27.

Time frame:
1 day at baseline before either intervention
Reported as:
Mean · units on a scale
Patient Health Questionnaire (PHQ-9)
units on a scaleCompleted Sleep RestrictionCompleted Sleep Extension
Patient Health Questionnaire (PHQ-9)4.73 ± 3.774.84 ± 3.80
Other pre-specifiedGeneralized Anxiety Disorder (GAD-7)

A 7-item anxiety scale used to identify probable cases of generalized anxiety disorder. Higher scores indicate more severe symptoms of anxiety. The minimum score is 0, and the maximum score is 28.

Time frame:
1 day at baseline before either intervention
Reported as:
Mean · units on a scale
Generalized Anxiety Disorder (GAD-7)
units on a scaleCompleted Sleep RestrictionCompleted Sleep Extension
Generalized Anxiety Disorder (GAD-7)5.23 ± 4.615.20 ± 4.70
Other pre-specifiedAssessing Smoking History

Smoking history will be assessed for daily smokers as smoking 5 or more cigarettes a day for the past one year and having smoked more than 100 cigarettes in lifetime or non-smoker defined as smoking fewer than 100 cigarettes in a lifetime and no smoking-not even a puff- in the last year. Using those definitions, we determined the number of participants who were smokers.

Time frame:
1 day at baseline before either intervention
Reported as:
Count of participants · Participants
Assessing Smoking History
ParticipantsCompleted Sleep RestrictionCompleted Sleep Extension
Assessing Smoking History2625
Other pre-specifiedBrief Wisconsin Inventory of Smoking Dependence Motives (WISDM-37)

The WISDM measures how strongly participants feel 11 potential motivations for smoking. Higher scores indicate being more strongly motivated to smoke. The minimum score is 11, and the maximum score is 77.

Time frame:
1 day at baseline before either intervention
Reported as:
Mean · units on a scale
Brief Wisconsin Inventory of Smoking Dependence Motives (WISDM-37)
units on a scaleCompleted Sleep RestrictionCompleted Sleep Extension
Brief Wisconsin Inventory of Smoking Dependence Motives (WISDM-37)41.44 ± 12.2542.14 ± 11.94
Other pre-specifiedTobacco Craving Questionnaire-SF (TCQ-SF)

The TCQ-SF contains 12 items to assess participants' craving to smoke cigarettes. Higher scores indicate stronger craving for tobacco. The minimum score is 12, and the maximum score is 84.

Time frame:
1 day at baseline before either intervention
Reported as:
Mean · units on a scale
Tobacco Craving Questionnaire-SF (TCQ-SF)
units on a scaleCompleted Sleep RestrictionCompleted Sleep Extension
Tobacco Craving Questionnaire-SF (TCQ-SF)42.08 ± 16.4442.84 ± 16.30
Other pre-specifiedAlcohol, Smoking, and Substance Involvement Screening Test (ASSIST)

The ASSIST asks questions assessing level of dependence to 10 different substances. Higher scores indicate more negative impacts of substance use. the minimum score is 0, and the maximum score is 280.

Time frame:
1 day at baseline before either intervention
Reported as:
Mean · units on a scale
Alcohol, Smoking, and Substance Involvement Screening Test (ASSIST)
units on a scaleCompleted Sleep RestrictionCompleted Sleep Extension
Alcohol, Smoking, and Substance Involvement Screening Test (ASSIST)5.65 ± 9.395.04 ± 9.03
Other pre-specifiedMinnesota Nicotine Withdrawal Scale (MNWS).

The MNWS is an 8-item measure designed to assess Smokers' cigarette withdrawal in the last 24 hours. Higher scores indicate more severe symptoms of nicotine withdrawal. The minimum score is 0, and the maximum score is 32.

Time frame:
1 day at baseline before either intervention
Reported as:
Mean · units on a scale
Minnesota Nicotine Withdrawal Scale (MNWS).
units on a scaleCompleted Sleep RestrictionCompleted Sleep Extension
Minnesota Nicotine Withdrawal Scale (MNWS).10.65 ± 6.5510.92 ± 6.54
Other pre-specifiedAlcohol Use Disorders Identification Test-Consumption (AUDIT-C).

A brief 3-item alcohol screening measure that identifies hazardous drinkers or those who have active alcohol use disorders. Higher scores indicate more symptoms of alcohol use disorder. The minimum score is 0, and the maximum score is 12.

Time frame:
1 day at baseline before either intervention
Reported as:
Mean · units on a scale
Alcohol Use Disorders Identification Test-Consumption (AUDIT-C).
units on a scaleCompleted Sleep RestrictionCompleted Sleep Extension
Alcohol Use Disorders Identification Test-Consumption (AUDIT-C).2.27 ± 2.632.28 ± 2.69
Other pre-specifiedPain, Enjoyment, General Activity (PEG) Scale

The PEG Scale contains 3 questions regarding how much pain has interfered with enjoyment of life and general activity in the past 7 days. Higher scores indicate greater interference from pain. The minimum score is 0, and the maximum score is 10.

Time frame:
1 day at baseline before either intervention
Reported as:
Mean · units on a scale
Pain, Enjoyment, General Activity (PEG) Scale
units on a scaleCompleted Sleep RestrictionCompleted Sleep Extension
Pain, Enjoyment, General Activity (PEG) Scale2.26 ± 2.542.25 ± 2.59
Other pre-specifiedTrauma History Scale (THS)

The THS is a brief 14-item self-report measure designed to assess traumatic events and how much those events are emotionally bothersome. The scale counts the number of traumas endorsed. The minimum value is 0, and the maximum value is 14.

Time frame:
1 day at baseline before either intervention
Reported as:
Mean · units on a scale
Trauma History Scale (THS)
units on a scaleCompleted Sleep RestrictionCompleted Sleep Extension
Trauma History Scale (THS)5.27 ± 9.95.28 ± 3.77
Other pre-specifiedPTSD Checklist-Short Form (PCL-5)

The short form of the 20-item PCL-5 which assesses the presence and severity of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) criteria for PTSD in the past month. The short form contains 4 items. Higher scores indicate more sever symptoms of PTSD. The minimum score is 0, and the maximum score is 16.

Time frame:
1 day at baseline before either intervention
Reported as:
Mean · units on a scale
PTSD Checklist-Short Form (PCL-5)
units on a scaleCompleted Sleep RestrictionCompleted Sleep Extension
PTSD Checklist-Short Form (PCL-5)3.50 ± 3.193.40 ± 3.21
Other pre-specifiedInternational Consultation on Incontinence Questionnaire-Overactive Bladder

4 items pertaining to overactive bladder symptoms experienced in the past 4 weeks. Higher scores indicate more symptoms of overactive bladder. The minimum score is 0, and the maximum score is 16.

Time frame:
1 day at baseline before either intervention
Reported as:
Mean · units on a scale
International Consultation on Incontinence Questionnaire-Overactive Bladder
units on a scaleCompleted Sleep RestrictionCompleted Sleep Extension
International Consultation on Incontinence Questionnaire-Overactive Bladder3.50 ± 3.193.48 ± 2.49
Other pre-specifiedInternational Physical Activity Questionnaire (IPAQ)

A set of questionnaires designed to assess physical activity and sedentary lifestyles. The questionnaire measures the minutes of physical activity per week, weighted by the intensity of the activity, referred to as the MET-min. The minimum value is 0, and a value that indicates high levels of activity per week would be 3000.

Time frame:
1 day at baseline before either intervention
Reported as:
Mean · MET-min per week
International Physical Activity Questionnaire (IPAQ)
MET-min per weekCompleted Sleep RestrictionCompleted Sleep Extension
International Physical Activity Questionnaire (IPAQ)7276.73 ± 8788.107558.20 ± 8848.89
Other pre-specifiedStandard Shiftwork Index (SSI)

A battery of self-report questionnaires measuring shift workers' sleep and stress outcomes. We are using the physical health subsections of this questionnaire. The scale counts the number of physical conditions endorsed. The minimum score is 0, and the maximum score is 23.

Time frame:
1 day at baseline before either intervention
Reported as:
Mean · units on a scale
Standard Shiftwork Index (SSI)
units on a scaleCompleted Sleep RestrictionCompleted Sleep Extension
Standard Shiftwork Index (SSI)2.65 ± 3.162.72 ± 3.21
Other pre-specifiedFatigue Severity Scale (FSS)

A 9-item scale measuring severity of fatigue and its effect on participants' activities and lifestyle. Higher scores indicate more severe fatigue. The minimum score is 9, and the maximum score is 63.

Time frame:
1 day at baseline before either intervention
Reported as:
Mean · units on a scale
Fatigue Severity Scale (FSS)
units on a scaleCompleted Sleep RestrictionCompleted Sleep Extension
Fatigue Severity Scale (FSS)27.23 ± 12.1827.36 ± 12.41
Other pre-specifiedAssessing Continuous Positive Airway Pressure (CPAP) Use

A 5-item survey designed by the research team to assessed whether or not participants are prescribed CPAP, and their adherence to using it. Using that questionnaire, we determined the number of participants who used a CPAP.

Time frame:
1 day at baseline before either intervention
Reported as:
Count of participants · Participants
Assessing Continuous Positive Airway Pressure (CPAP) Use
ParticipantsCompleted Sleep RestrictionCompleted Sleep Extension
Assessing Continuous Positive Airway Pressure (CPAP) Use00

Adverse events

Collected over Baseline survey completion to discharge from sleep center after second sleep condition, up to 2 months. Non-serious events are listed at a 0% frequency threshold.

Adverse event summary by group
GroupDeathsSeriousOther
Completed Sleep Restriction0/26 (0%)0/26 (0%)0/26 (0%)
Completed Sleep Extension0/25 (0%)0/25 (0%)0/25 (0%)

Baseline characteristics

Age, Continuous
Age, Continuous(years)Sleep Restriction First, Then Sleep ExtensionSleep Extension First, Then Sleep RestrictionTotal
Mean44.50 ± 10.4145.59 ± 10.4245.14 ± 10.24
Sex: Female, Male
Sex: Female, Male(Participants)Sleep Restriction First, Then Sleep ExtensionSleep Extension First, Then Sleep RestrictionTotal
Female81220
Male459
Race (NIH/OMB)
Race (NIH/OMB)(Participants)Sleep Restriction First, Then Sleep ExtensionSleep Extension First, Then Sleep RestrictionTotal
American Indian or Alaska Native000
Asian000
Native Hawaiian or Other Pacific Islander000
Black or African American61016
White6713
More than one race000
Unknown or Not Reported000
Ethnicity (NIH/OMB)
Ethnicity (NIH/OMB)(Participants)Sleep Restriction First, Then Sleep ExtensionSleep Extension First, Then Sleep RestrictionTotal
Hispanic or Latino000
Not Hispanic or Latino121729
Unknown or Not Reported000
08

Study locations

1 site
  • University of Alabama, Birmingham
    Birmingham, Alabama 35226, United States
09

References and documents

Study documents

  • Study protocol · Oct 2, 2023
  • Statistical analysis plan · Apr 1, 2026

Documents are hosted by the registry — open the source record to download them.

10

Updates

Tracking since Sep 25, 2026
No changes since tracking began. The registry record was last updated on Aug 25, 2026, before this site started recording changes on Sep 25, 2026. Its history is on ClinicalTrials.gov ↗
11

Registry details

Key details

Study ID
NCT03968900
Lead sponsor
University of Alabama at Birmingham
Collaborators
University of Oklahoma, National Institute on Drug Abuse (NIDA)
Responsible party
Karen Cropsey (Associate Professor, University of Alabama at Birmingham) — Principal investigator
First posted
May 30, 2019
Start date
Jan 1, 2021
Primary completion
Apr 1, 2025
Completion
Apr 1, 2025
Results posted
Jul 31, 2026
Last update
Aug 25, 2026

Study contacts

Karen L Cropsey, Psy.D.
principal investigator · University of Alabama at Birmingham

Oversight

Data monitoring committee
Yes
FDA-regulated drug
No
FDA-regulated device
No
View the source record on ClinicalTrials.gov ↗

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