The Study
Effect of daylight LED on visual comfort, melatonin, mood, waking performance and sleep
This study watched the same group of people under two different lights to see how they felt and slept. It can show that one light was linked to feeling better or sleeping differently, but it can't prove the light caused those changes because we don’t know for sure how the study was run.
Analysis score
Maximum 90 for a randomized controlled trial.
Where the score came from
Scientists tested if a type of light that looks more like sunlight makes people feel better and sleep better, even if it’s just as bright as normal light.
Where does this study sit?
Reviews of RCTs (Meta-analyses)
Max 100Randomized Trials
Max 90Reviews of Cohort Studies
Max 85Cohort Studies
Max 72Reviews of Case-Control Studies
Max 63Case-Control Studies
Max 58Cross-Sectional & Case Series
Max 50Expert Opinion
Max 532 / 100
Quality score
Participants are randomly assigned to treatment or control groups, minimizing bias. The gold standard for testing whether an intervention causes an effect.
Key takeaways
Summary
Based on the study abstract and findings.
- 1The results suggest that even when lights seem equally bright, the hidden quality of light can affect how we feel and sleep.
- 215 young men felt more comfortable, alert, and happy with daylight-like LED light.
- 3Their brain showed more deep sleep activity afterward, even though their daytime focus and melatonin didn’t change.
Score breakdown, methodology, conflicts of interest, evidence analysis & raw study data
Publication
Journal
Lighting Research & Technology
Year
2019
Authors
Christian Cajochen, M. Freyburger, T. Basishvili, T. Basishvili, C. Garbazza, F. Rudzik, C. Renz, Kumpei Kobayashi, Yasuhiro Shirakawa, Oliver Stefani, J. Weibel
Related Content
Claims (4)
Being around blue light at night, like from phones or screens, might keep your body from making the sleep hormone melatonin because it keeps stress hormone levels high, making it harder to fall and stay asleep.
Using a special kind of bright white LED light that looks more like natural daylight might make young guys feel more awake, comfortable, and in a better mood during the day—even if it’s just as bright as regular office lighting.
If young, healthy guys are exposed to daylight-like LED lights during the day, they might sleep more deeply at night — even if their alertness and sleep hormone levels don’t change much.
In healthy young guys, better-quality daylight-like LED lights don’t seem to change daily melatonin levels or brain performance like focus and memory — so upgrading light quality might not always boost health or thinking skills.
Not medical advice. For informational purposes only. Always consult a qualified healthcare professional before making health decisions.