Dynamic versus static LED-lighting for inpatients with major depression: Long-term antidepressant effects and short-term sleep improvement in a randomized controlled clinical trial

Translational research has shown a profound impact of daylight and electrical lighting on circadian rhythms, sleep, mood, and alertness. Dynamic LED-lighting can mimic daily and seasonal changes in daylight by continuous changes in intensity and spectral distribution throughout the 24-hour day. The current study assessed the clinical effect of dynamic LED-lighting in a randomized controlled setup. In an affective disorders ward, 10 single patient rooms were fitted with a dynamic LED-lighting system, replacing the existing lighting, able to switch between a dynamic or a static mode. In the dynamic mode, daytime Melanopic Daylight Equivalent Illuminance (M-EDI) peaked at 10:30h with 576 lx M-EDI vs. 66 lx in the static mode. During the evening, the dynamic mode gradually reduced intensity to 0.3 lx M-EDI, with the static mode staying at 66 lx. Patients with major depression were randomly allocated to a static or a dynamic lighting mode in their room, lasting three weeks, with weekly assessments, and after 6 months. The primary outcome was the change in scores on the HAM-D6 scale from baseline to week 3. In all, 60 patients were included in the study with a 96.7% follow-up of the primary outcome. On the 6-item Hamilton Depression Rating Scale (HAM-D₆) scale, a significantly greater antidepressant effect of the dynamic light was seen at week 3 for females (71%) (<i>p</i> = 0.02), but not for the whole group (<i>p</i> = 0.47). At 6 months, a significantly greater effect of dynamic light was seen for the whole group (<i>p</i> = 0.03). Sleep diaries showed significantly longer sleep (<i>p</i> = 0.02), fewer awakenings (<i>p</i> = 0.04), and later sleep offset (<i>p</i> = 0.03) with dynamic light, for the whole group. The dynamic lighting system was well functioning. Participants were most satisfied with the dynamic light. These findings should be tested in larger studies with measurement of individual light exposure.