Consequences of Caffeine Intake in Sleep Restricted Teenagers

Consequences of Caffeine Intake in Teenagers: Effects on Sleep, Reward Processing, Risk Taking, and Underlying Cerebral Mechanisms Under Conditions of Sleep Restriction

The goal of this clinical trial is to systematically investigate two prominent factors in teenagers' daily life: Caffeine and sleep restriction (SR) and their combined influence on sleep, cognition, and behavior in healthy adolescents. The main questions it aims to answer are:

The effects of caffeine under conditions of SR and SE:

• on sleep pressure and sleep continuity.
• on BOLD activity differences in reward related areas during a reward task (monetary incentive delay task) and on reaction times (behavioral aspect) in the same task.
• on BOLD activity differences during a risk taking task (wheel of fortune task) and on risky decision-making (behavioral aspect) in the same task.

Participants will be either in the SR or SE condition (between-subject). The protocol consists of 2x of approximately one week in which a participant will receive caffeine or placebo (within-subject) at the last two evenings.

The experiment consists of an ambulatory and a laboratory phase:

• The ambulatory phase consists of 5 nights, including 3 stabilization nights (8h sleep opportunity) prior to 2 nights consisting of either SR with 6h sleep opportunity or SE with 9.5h sleep opportunity. Participants will wear an actiwatch and fill out sleep diaries during this period.
• The laboratory phase will be the 6th evening, night and morning of the protocol and will be spent in our lab. Participants will do the following:
• treatment (caffeine vs. placebo) intake
• saliva sampling
• drug screening
• cognitive tests, including risk-taking and reward task
• filling in questionnaires (sleep diary, sleep quality, sleepiness, mood, expectancy)
• waking and sleep with EEG

The next day, participants will undergo an fMRI scan, including the following:

• resting-state scan
• structural scan
• arterial spin labeling scan
• reward task scan
• risk-taking task scan

Around the scan, participants will fill out/undergo:

• saliva sampling
• questionnaires (reward task, mood, sleepiness, expectancy)

Inclusion Criteria:

• Age ≥ 14 and ≤ 17
• Clinically healthy
• Signed consent form of participant and legal guardian

Exclusion Criteria:

• Inability to operate tasks or understand the study information
• Participation in other clinical trials <3 months prior to any possible study start date
• BMI P3 < BMI-PC < P97
• Any general health concerns or disorders (previous diagnosis of heart/cardiovascular/nephrological/endocrinological/diabetic/metabolic/chronobiologic/ psychiatric/neurological [particularly epilepsy and parasomnia] conditions) which may make participants vulnerable to potential negative effects of SR or caffeine or which may affect outcome measures
• Unavailability to complete the two study protocol weeks within a three-month period
• Trans meridian travel (>2 time zones) <1 month before any possible study start date
• Shift work <3 months prior to any possible study start date
• Extreme chronotype MSFSC < 3:00 / MSFSC > 6:00 according to MCTQ
• Subjective sleep duration on school days <7h or >9h according to MCTQ
• Metallic prosthesis, metallic implants, or non-removable objects in the body (e.g., splinters, piercings) which affect MRI safety
• Tattoos with larger diameter than 10cm or above shoulder area, affecting MRI safety
• Claustrophobia
• Difficulties or problems in physical well-being and mental health based on the Swiss norm (T< 35) for all genders aged 12-18 according to KIDSCREEN-27
• Daily nicotine use
• Use of medications or drugs that have contraindications and/or effects on outcome measures or use of specific drugs indicated in drug test
• Use of alcohol to an extent that it is likely to have contraindications and/or effects on outcome measures
• Any indication of previous withdrawal or oversensitivity to caffeine
• Sleep quality >5 according to PSQI
• Problems of EEG compatibility
• Sleep efficiency <70%
• Identification of sleep disorders
• Pregnancy
• Deviation from the stabilisation sleep-wake schedule by +-60 mins
• Deviation from protocol sleep-wake schedule by +-30 mins