Beneficial Effects of Daytime Light Exposure and Physical Activity on the Human Circadian Clock and Sleep

Summary

This study is to examine the circadian phase-shifting effects of daylight and physical activity (primary endpoint: shift in dim-light melatonin onset (DLMO)) as well as their effects on sleep the ensuing night and analyzes how different spectral characteristics of daylight and physical activity affect the biological clock and sleep.

There are two types of interventions in a within-between study plan: - Within participants: light conditions will be varied during daytime in three 7-hour light exposure protocols (usual office lighting, natural daylight, natural daylight with "blue"-light filtering glasses). - Between participants: physical activity levels (rest vs. 4 hours of moderate activity, i.e., hiking) will be varied. Eligible volunteers are invited to partake in the three-week study schedule, including three experimental visits and in-between ambulatory sleep-wake and light exposure tracking. On study intake, participants are randomly assigned to either the 'hike' or 'rest' activity subgroup. The 'resting subgroup' will be allowed to study, read, etc. during the experimental conditions, whereas the 'hiking subgroup' will have 4 hours of scheduled moderate physical activity during each LE condition starting 3 hours after waking up.

Following the screening procedure and an adaptation night to screen for sleep disorders, eligible participants will be matched with a 'partner'. One will be assigned to the rest (A), the other to the hiking (B) subgroup. LE protocols within each subgroup are identical and participants from each pair will undergo all light conditions on the same day to minimize variability due to e.g., weather conditions.

Conditions

• Circadian System

Interventions

OTHER

LE protocol 1: exposure to artificial light

Participants stay in the lab with light mimicking usual office lighting. On days 8, 15, and 22, participants start the experimental protocol 5 hours before HBT: questionnaires, behavioural responsiveness (assessed by PVT), saliva samples for melatonin measurements (until HBT and two more following awakening the next day). Participants will go to bed at HBT and get up 8h later in the morning. Their sleep will be assessed with PSG recordings.

OTHER

LE protocol 2: natural daylight

Participants spend the same time outdoors in natural daylight. On days 8, 15, and 22, participants start the experimental protocol 5 hours before HBT: questionnaires, behavioural responsiveness (assessed by PVT), saliva samples for melatonin measurements (until HBT and two more following awakening the next day). Participants will go to bed at HBT and get up 8h later in the morning. Their sleep will be assessed with PSG recordings.

OTHER

LE protocol 3: natural daylight with reduced short-wavelength proportions

Participants spend the same time outdoors in natural daylight wearing tinted glasses that filter out short-wavelength light proportions. On days 8, 15, and 22, participants start the experimental protocol 5 hours before HBT: questionnaires, behavioural responsiveness (assessed by PVT), saliva samples for melatonin measurements (until HBT and two more following awakening the next day). Participants will go to bed at HBT and get up 8h later in the morning. Their sleep will be assessed with PSG recordings.

Sponsors & Collaborators

• Swiss National Science Foundation

  collaborator OTHER

• University Hospital, Basel, Switzerland

  lead OTHER

Principal Investigators

• Christine Blume, Dr. med. · Centre for Chronobiology, Psychiatric Hospital of the University of Basel

Study Design

Allocation

RANDOMIZED

Purpose

BASIC_SCIENCE

Masking

NONE

Model

SEQUENTIAL

Eligibility

Min Age

18 Years

Max Age

35 Years

Sex

ALL

Healthy Volunteers

Yes

Timeline & Regulatory

Start

2023-04-27

Primary Completion

2025-09-12

Completion

2025-09-12

Countries

• Switzerland

Study Locations