Impact of Sleep Restriction in Women
Condition: Sleep; Cardiovascular Disease; Obesity
MeSH terms: Cardiovascular Diseases
Study type: Interventional

Summary: 
      The overall goal of this project is to test the hypothesis that long-term, sustained sleep
      restriction (SR), in women, will lead to increased cardio-metabolic risk. This will be
      characterized by increases in visceral adiposity, unhealthy lifestyle behaviors (poor dietary
      quality and low physical activity) and cardio-metabolic risk factors (blood pressure, glucose
      intolerance) relative to habitual sleep (HS). The investigators expect these changes to be
      worse in pre- compared to post-menopausal women.
    

Detailed description: 
      This project is funded by the American Heart Association Go Red for Women Strategically
      Focused Research Network (SFRN). This SFRN includes two separate projects: Clinical Science
      Project (PI, St-Onge) and Basic Science Project (PI, Jelic). Women are enrolled in the
      Clinical Science project and given the option to enter the Basic Science project. Each
      project (clinical and basic) has its own separate primary and secondary outcomes. For the
      Clinical Science project, primary outcomes are glucose tolerance and ambulatory and office
      blood pressure; and secondary outcomes are body composition and circulating inflammatory
      markers. For the Basic Science project, the primary outcomes are flow mediated dilatation of
      the brachial artery (FMD) and secondary outcomes are endothelial cell oxidative stress and
      inflammation. The results of these two projects will be reported in separate and in combined
      publications.

      This study will be a randomized, crossover, outpatient sleep restriction (SR) study with 2
      phases of 6 weeks each, with a 6 week wash-out period between the phases. Sleep duration in
      each phase will be the participant's regular bed- and wake times during the habitual sleep
      (HS) phase and HS minus 1.5 hours in the SR phase. During the HS phase, participants will be
      asked to follow a fixed bedtime routine based on their screening sleep schedule. During the
      SR phase, participants will be asked to keep their habitual wake time constant but delay
      their bedtime to achieve a reduction of 1.5 hours in total sleep time.

      On the first day of each study phase (baseline), participants will come to the research
      center in the morning after an overnight,12 hour fast. Participants will have anthropometric
      measurements taken and will then be taken to the department of Radiology to undergo magnetic
      resonance imaging (MRI) scanning to assess body composition. Flow-mediated dilatation will be
      performed in the Cardiovascular Ultrasound Laboratory followed by endothelial cell harvesting
      (Basic Science project). A sample of cells lining the blood vessel (forearm vein) will be
      taken to assess endothelial function. Women will undergo an oral glucose tolerance test
      (Clinical Science project). Blood samples will be taken for hormone measurements (insulin,
      cortisol). Participants will begin the fixed bedtime routine that night. These baseline
      measurements will be repeated at endpoint, 6 weeks later. Body weight and waist circumference
      will be measured weekly and fasting blood samples will be taken at weeks 3 and 4 during
      adherence check visits.

      To verify that participants adhere to the sleep protocol, they will be asked to keep a sleep
      diary and wear an activity monitor 24 hours/day. Participants will wear an actigraph GT3X+ on
      their wrist, which will serve to track their sleep duration, sleep timing, and physical
      activity. Two weeks prior to randomization and during the washout period, participants will
      also wear the actigraph watch and keep a sleep diary to verify sleep duration and sleep-wake
      schedule. In addition to achieving an average sleep of 7-9 hours/night, by wrist actigraphy,
      participants will only be enrolled if they achieve 7 hours of sleep for at least 10 of the 14
      nights of screening and have <4 nights with <6 hours of sleep. At the time of randomization,
      a urine pregnancy test and drug screen will be performed. Participants will be asked to
      abstain from caffeine and alcohol intake for 24 hours prior to the start. Between study
      phases, if participants have not returned to baseline sleep patterns within the 6 week
      washout period, an additional 2-4 week washout period will be provided. This washout length
      will ensure that women are in the same phase of their menstrual cycle at the start of each
      experimental phase.
    

Intervention name(s): Sleep Restriction
Intervention type(s): Other
Intervention description(s): Mild sleep restriction (-1.5 h/night) over a period of 6 weeks
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: None (Open Label)
Primary purpose: Prevention
Keywords: Obesity; Metabolic Disorders