The indoor light environment of hospital wards may affect functions and symptoms that are central to the process of inpatient recovery, including sleep, anxiety, well-being, and mood.

To assess whether interventions in light improves recovery in hospitalized patients across all medical specialties.

We systematically searched and reviewed the literature for RCT's on adult inpatients where any light intervention were compared to standard care or placebo. We reviewed effects of light on various outcomes, and compared differences in administration, timing, color, and intensity of the light.

We identified 2330 titles, of which 32 met our predefined selection criteria. Choice of administration, timing, wavelengths, and intensity varied. However, most studies investigated bright light therapy with high intensity and short exposure time, others low-intensity light at night filtered of wavelengths in the blue spectrum, and yet others the use of dawn simulation. Comparators were either placebo lamps with low intensity or regular indoor light. Most studies were performed on psychiatric inpatients, showing that bright light therapy is an effective aid in recovery of major depression. Across medical specialties, several studies reported improved sleep quality during the light intervention. Other studies found a lower rate of delirium. In elderly patients with dementia, studies found light interventions to relieve agitation and confusion.

Light may ease a broad range of symptoms and behaviors across inpatient categories. The intervention is inexpensive, well tolerated, and non-invasive. This study underlines intelligent lighting design as an interesting, yet under-explored, non-pharmaceutical treatment.

The authors have not supplied their declaration of competing interest.