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The 14,000 K lamp, which was perceived as bluish-white or “blue sky” light, was chosen for installation. According to the model of human circadian phototransduction (the process in which the retina converts light signals into neural signals for the circadian system), the 14,000 K lamp can affect the circadian system at light levels much lower than those used in previously published studies (400-500 lux compared with > 2,500 lux).9 Changes in lamp spectrum and total irradiance emitted offered an 8-fold increase in circadian stimulation over the existing lighting. The LSC Human Subjects Review Board approved the project.
Measurements in the CLC ward indicated that existing lighting in the halls and rooms was dim—between 75 lux and 100 lux. Although this level was similar to those reported in the literature and satisfactory for reading and general activities, it likely was not sufficient to stimulate residents’ circadian systems.4 The dayroom was selected for lamp installation, because it was used for dining and many daily activities, thus maximizing the number of veterans who could benefit from exposure to the new type of lighting.
The dayroom was large, 35 feet by 40 feet, and had windows on 3 sides. Illumination came from the windows, which had blinds and/or window air conditioning units, and 13 ceiling fluorescent light fixtures, each with 4 lamps. Using multiple light meter measurements, 14,000 K lamps were installed in 7 of 13 light fixtures to minimize significant engineering changes while maximizing the illumination.
The Table shows the illumination in lux in the dayroom with and without the 14,000 K lighting. Horizontal light levels, 3 feet above the floor and measured in a horizontal direction, increased from between 300 lux and 350 lux to 500 lux. The lamps added more light and contrast while not increasing glare or causing excessive brightness.
Five veterans with dementia consented (with family members involved), but due to actigraph malfunction, only 3 of the 5 participants completed the 2 data collection periods: 7 continuous days of rest/activity measurements under the regular ward lighting and experimental lighting plan with a 3-week adaptation period in between. Results were generally in the expected direction after exposure to new lighting: Sleep latency (time in bed until the first 20 minutes of sleep) improved, decreasing by 23%, and sleep efficiency increased by 6.6%. The new lighting was well received; there were no reports about heat or glare, and the staff frequently commented that the room looked as though it was in reflected sunlight. A new CLC building was subsequently built with excellent window access and lighting. Therefore, the lighting project was moved to the home of a test subject.
Home Lighting Projects
In a feasibility pilot, the light exposure and rest activity of an older veteran with dementia and his spouse was measured in their home.10,11 Neither were exposed to light > 400 lux for much of the 7 continuous days of measurement, and the majority of their waking hours was spent in light < 100 lux (insufficient for reading). Actigraphy data indicated fragmented nighttime sleep for both participants with the caregiver sleeping much less than the veteran.
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This pilot suggested that appropriate circadian lighting in the home could positively influence circadian sleep-wake cycles. Therefore, in collaboration with colleagues at the LRC at RPI and GE, the authors initiated a study funded by the National Institute on Aging (PI: Figueiro M) to install home lighting customized to the rooms used most during the day by veterans with dementia. In phase 1, the results showed that circadian disruption in those with dementia in winter months was significantly higher than in the summer months and that healthy older adults received more circadian light and were less disrupted than those with dementia.12 Phase 2 of the study, which is a pretest/posttest control group intervention of circadian lighting, is ongoing.
Conclusion
The research has not yet provided a definitive answer about whether circadian-active light can improve circadian synchrony and thereby benefit patients with dementia and their caregivers. Work in this area is translational and ongoing: The issues of dosing, timing, and delivery are still open questions for further research. The next steps related to testing light delivery and dose could include tailoring the daytime lighting in day care centers with blue lighting and/or testing the use of blue light goggles.