Evening Blue‑Depleted Light Environment in Hospitals and Nonvisual Effects

Summary

This randomized crossover trial tested whether changing hospital evening lighting to a blue-depleted spectrum (warmer light with less blue wavelength) would better support circadian health. Twelve healthy adults stayed for five days in each lighting condition: standard hospital lighting and the blue-depleted system. Compared with standard lighting, the blue-depleted environment caused less melatonin suppression, shifted melatonin onset earlier, and led to slightly longer total sleep time and more REM sleep. Participants also showed lower neurocognitive arousal, with no significant side effects reported.