Impact of Sleep Restriction in Women

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. They will then return to the the
clinic for an oral glucose tolerance test. A blood sample will be taken for hormone
measurements, and a sample of cells lining the blood vessel (forearm vein) will also be taken
to assess endothelial function. 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 week 3
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.

Inclusion Criteria:

- Age 20-65 years old

- All racial/ethnic groups

- Body mass index 25-29.9 kg/m2

- Sleep 7-9 h in bed/night with no daytime nap

- Normal scores on:

Pittsburgh Quality of Sleep Questionnaire Epworth Sleepiness Scale, Berlin Questionnaire,
Sleep Disorders Inventory Questionnaire, Beck Depression Inventory, Composite Scale of
Morningness/Eveningness, Three Factor Eating Questionnaire

Exclusion Criteria:

- Smokers (any cigarettes or ex-smoker <3 years)

- Neurological, medical or psychiatric disorder

- Diabetics

- Eating and/or sleep disorders

- Contraindications for MRI scanning

- Travel across time zones within 4 wk

- History of drug and alcohol abuse

- Shift worker (or rotating shift worker)

- Caffeine intake >300 mg/d

- Oral contraceptive use or hormone replacement therapy

- Heavy equipment operators

- Commercial long-distance drivers.