The Cognitive and Metabolic Effects of Sleep Restriction in Adolescents
Condition: Sleep; Sleep Restriction
Study type: Interventional

Summary: 
      The aim of this study is to examine the neurobehavioural and glucose metabolic responses to
      two successive cycles of sleep restriction and recovery in adolescents, and to determine the
      benefits of napping on cognitive performance, alertness, mood and glucose metabolism. Using a
      split-sleep design, 60 participants, aged 15 to 19 years old, are divided into a nap and a
      no-nap group. Both groups undergo two cycles of sleep restriction and recovery over a period
      of 15 days. The no-nap group receives a 6.5-hour sleep opportunity on sleep restriction
      nights, with no daytime nap opportunity. The nap group receives a 5-hour sleep opportunity on
      sleep restriction nights, and has a 1.5-hour nap opportunity the following afternoon.
    

Detailed description: 
      The present study investigates whether a continuous stretch of night time sleep (6.5 hours)
      will lead to better neurobehavioural outcomes relative to nocturnal sleep restriction (5
      hours) and daytime nap (1.5 hours) of the same total duration, and how sleep restriction
      affects glucose metabolism. The 15-day protocol is conducted in a dormitory on 60 high school
      students, aged 15 to 19 years old. Participants are assigned to a nap or no-nap group. Both
      groups start with two 9-hour adaptation and baseline nights, followed by two successive
      cycles of sleep restriction (5-h time in bed (TIB); 01:00-06:00 or 6.5-h TIB; 00:15-06:45)
      and recovery (9-h TIB; 23:00-08:00). Following each sleep-restricted night, the nap group
      receives a 1.5-h nap opportunity, while participants in the no-nap group watch a documentary.
      Throughout the protocol, sleep-wake patterns are assessed with actigraphy and
      polysomnography. Sleepiness levels, mood, vigilance, working memory / executive functions,
      and speed of processing are assessed 3 times daily (10:00, 16:15, and 20:00). Other cognitive
      functions such as memory and mindfulness levels are investigated through computer-based
      tasks. Glucose metabolism is measured using oral glucose tolerance tests in the mornings
      after the second baseline night, the third night of sleep restriction and second recovery
      night in the first cycle, as well as the last sleep restriction night in the second cycle.

      All participants stay in air-conditioned, twin-share bedrooms with en-suite bathrooms.
      Bedroom windows are fitted with blackout panels to ensure participants are not woken up
      prematurely by sunlight. Earplugs are provided, and participants are allowed to adjust the
      temperature of their bedrooms to their personal comfort. Three main meals are served each
      day, with snacks being provided for upon request. Caffeinated drinks, unscheduled sleep, and
      strenuous physical activities are prohibited.

      Outside of scheduled sleep, meal, and cognitive testing times, participants spend the
      majority of their free time in a common room that is illuminated by natural and artificial
      lighting. They are allowed to read, play non-physically exerting games, watch videos, and
      interact with research staff and other participants. Participants are under constant
      supervision by the research staff.
    

Intervention name(s): Nap
Intervention type(s): Behavioral
Intervention description(s): Looking at the difference between continuous sleep opportunities and split-sleep opportunities.
Allocation: Randomized
Intervention model: Parallel Assignment
Masking: None (Open Label)
Primary purpose: Basic Science
Keywords: Nap; Recovery Sleep; Cognitive Functions; Glucose Metabolism; Neurobehavioral Functions; Mood; Subjective Sleepiness