Impact of Light Therapy on People with Dementia: An Evidence-Based Review

Fatemeh Motamed Rastegar (Georgia Institute of Technology)

Light therapy is increasingly proposed as a nonpharmacological treatment for a variety of health-related issues including treatment of Elderly People with Dementia (EPD). While the visual effects of light on older adults are well-documented and integrated into design guidelines, evidence related to the non-visual effects of lighting is less studied, especially for EPD. This review synthesizes the available evidence on non-visual effects of light on EPD to identify lighting conditions that are most favorable for generating positive non-visual outcomes.

We carried out a systematic review of thirty-four empirical studies on the non-visual impacts of light on EPD, which largely are focused on the areas of sleep, alertness, mood and cognitive performance. The intervention methods used can be classified into two categories: 1) light intensity, 2) color temperature or wavelength manipulation.

Results indicate that while subjects report significant improvements in behavioral symptoms and cognitive functions when they get exposed to high levels of light, not many objective measurements affirm these effects. In the second category, preliminary objective evidence shows that short wavelength light can slow down cognitive decline and health decline; however, this evidence is not consistent across all studies. Interestingly, among the collected studies, some features such as the impact of blue light on alertness decreases substantially as we age; while others like the response to green and violet lights remain unchanged.

Altogether, we identify a growing body of evidence on the therapeutic benefits of lighting and its use in treating mental and behavioral disorders among the EPD. The experiments using light as therapy have improved our understanding of the underlying principles, but the integration of healing aspects of lighting in design practice and guidelines is still lacking. Finally, we propose a framework to facilitate further study and analysis of effect of light.