The blue light is the strongest time-giver of the human circadian rhythm. Patients admitted for rehabilitation often lack sufficient blue light in daytime due to absent in natural light during hospitalization.

This study is a parallel RCT study (quasi randomization). We screened 256 and included 90 patients over a year from the acute stroke unit with indication for in-hospital neurorehabilitation for more than 2 weeks and randomized them to either the naturalistic light unit or the control unit. We measured depressive mood, fatigue, anxiety, well-being, cognition, subjective sleep quality and the diurnal rhythm of melatonin and cortisol blood levels. 

The assessments were performed at the inclusion and again at discharge. A total of 71 patients completed the study.

Depressive mood, well-being, anxiety and fatigue were found significantly lower in the intervention group at discharge compared with the control group. No significant difference was found regarding sleep quality, sleepiness and cognition.

Significantly increased 24 hours’ melatonin levels and morning cortisol levels together with evolved melatonin rhythmicity were discovered in the intervention unit at the time of discharge. 

This study shows for the first-time beneficial effect of ambient naturalistic light in long time hospitalized stroke patients. 

Principal supervisor: Helle Klingenberg Iversen MD. DMSci.
Associate Research Professor, Clinical Stroke Research Unit, Department of Neurology, Faculty of Health Sciences, University of Copenhagen, Rigshospitalet, Glostrup.

Co-supervisor: Poul Jørgen Jennum MD. DMSci. Professor
Danish Center for Sleep Medicine, Department of Neurophysiology Faculty of Health Sciences, University of Copenhagen, Rigshospitalet, Glostrup.

Co-supervisor: Birgit Agnes Sander MSci. PhD.
Department of Ophthalmology, Copenhagen University Hospital, Rigshospitalet, Glostrup.

Supervisor: Henriette Pia Sennels MD. PhD.
Department of clinical biochemistry, Copenhagen University Hospital, Rigshospitalet, Glostrup.