Sleep quality / circadian light
Red light before bedtime effects on sleep and mood randomized PSG study
Pan R, Zhang G, Deng F, Lin W, Pan J. Frontiers in Psychiatry. 2023.
A randomized PSG study found 1 hour of 625 nm red light before bedtime increased subjective alertness, anxiety, and negative emotions, with mixed sleep-structure effects.
Evidence grade
low
Effect direction
mixed
Panel relevance
partially-replicable
Key findings
- Participants with insomnia symptoms and healthy participants received red light, white light, or black-control conditions for 1 hour before bed.
- Red light increased subjective alertness, anxiety, and negative emotions in both healthy and insomnia-symptom groups.
- The study is a useful caution against claiming evening red light is automatically sleep-promoting.
Protocol details
| Wavelengths | 625 nm |
|---|---|
| Irradiance | Not reported mW/cm2 |
| Fluence | Not reported J/cm2 |
| Session time | 60 minutes |
| Frequency | Single bedtime exposure in study protocol |
| Duration | Not reported |
| Treatment area | Visual light exposure |
| Device type | Red light room/panel exposure |
Caveats
- This is visual red-light exposure, not necessarily tissue-targeted PBM.
- Sleep content should separate low-illuminance circadian lighting from high-irradiance PBM dosing.