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Title:Impacts of tuning ambient illumination on sleep quality, mood, and cognitive performance in older adults
Author(s):Shishegar, Nastaran
Director of Research:Boubekri, Mohamed
Doctoral Committee Chair(s):Boubekri, Mohamed
Doctoral Committee Member(s):Rogers, Wendy A.; Stine-Morrow, Elizabeth A. L.; Yi, Yun Kyu
Department / Program:Architecture
Discipline:Architecture
Degree Granting Institution:University of Illinois at Urbana-Champaign
Degree:Ph.D.
Genre:Dissertation
Subject(s):Lighting
Older Adults
Architectural Lighting Design
Circadian Rhythms
Sleep
Mood
Depression
Cognitive Performance
Abstract:Population aging is one of the most urgent demographic matters of the 21st century. As a person ages, health expenses usually rise so as to increase vulnerability, especially where social and economic protections are lacking. Thus, the need for increased research on factors to support late-life health is more crucial than ever before. Older adults are at higher risk for sleep dysfunctions, depression, and cognitive impairments as aging is associated with several physical, biological, and social changes. Proper lighting condition is one of the non-pharmacological solutions that could potentially play an important role in improving health and well-being in older adults. In addition to the visual impact, light causes extensive emotional and biological aspects that influence circadian rhythms, sleep, mood, and cognitive performance. Appropriate lighting design should consider both visual and non-visual effects of light. Research suggests that a healthy lighting condition should provide individuals with exposure to light with the right spectrum and illuminance level at the right time; namely, lighting conditions during the daytime and nighttime are to be different. Hence, designers need to have a whole-day approach towards lighting. Timing and duration of exposure are two factors that are usually not considered in the process of lighting design. This study aimed to evaluate the effects of two whole-day ambient lighting interventions on sleep quality, mood, and cognitive performance in older adults. Both lighting interventions were designed to create a direct/indirect ambient illumination that provided a high illuminance level (500 lux) in the morning (8:00 – 12:00), followed by gradually lower illumination throughout the rest of the day, reaching 100 lux in the evening (after 20:00). One lighting condition (L1) delivered a constant Correlated Color Temperature (CCT) of 2700ºK. In the other lighting condition (L2), the CCT was changing in a range of 6500ºK – 2700ºK from morning towards evening. We recruited 21 healthy older adults (mean age = 78.81 years; 16 females and 5 males), from three senior residential communities in Saint Louis, Missouri, and Chicago, Illinois. Lights were placed in the living rooms of the participants around their most favorite seating spot for 18 days. The study was designed as a counterbalanced crossover experiment, with two baseline measurements (before and after the interventions) and 18 days of interventions. Participants were exposed to each lighting condition for nine days. We employed wrist-worn actigraphy measures (41 days) and standardized measures of sleep quality, mood, and cognitive performance before, during, and after interventions. As hypothesized, we found improvements in objective and subjective sleep metrics, mood, and cognitive functions after exposure to both lighting conditions; there were significantly more improvements for the L2 intervention. This research found promising evidence that a whole-day lighting scheme with varying intensity and CCT, tailored to meet circadian and visual performance needs of older adults, could be an effective design solution to create a healthy and healing living environment in senior livings and promote sleep, mood, cognitive functions, and hence the quality of life in their senior residents.
Issue Date:2020-07-06
Type:Thesis
URI:http://hdl.handle.net/2142/108668
Rights Information:Copyright 2020 Nastaran Shishegar
Date Available in IDEALS:2020-10-07
Date Deposited:2020-08


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