Associations between light exposure and sleep timing and sleepiness while awake in a sample of UK adults in everyday life

This study investigated the relationship between light exposure and sleep quality, timing, and daytime alertness in 59 UK adults using wearable light sensors and sleep diaries. It found that exposure to bright light in the morning reduced sleep inertia (morning grogginess) and improved daytime alertness, while excessive light exposure in the evening and during sleep delayed bedtime and increased sleep onset latency. Most participants failed to meet recommended light exposure levels, highlighting the importance of well-timed light exposure to support circadian health, sleep quality, and cognitive function.

Maximize exposure to natural bright light in the morning and minimize light exposure, particularly from screens and artificial sources, in the 3 hours before bedtime to improve sleep timing and reduce grogginess. This observational study emphasizes the timing of light as a key factor in maintaining circadian health and better sleep, though individual results may vary. Implementing consistent daily light patterns can enhance sleep and daytime alertness.