Table Talk

Creative Solution to Deliver Circadian-Effective Light

By Allison Thayer, MS, Light and Health Research Center at Mount Sinai

Why Should I Brighten My Day?

Bright light during the day and dim to dark light at night is essential for human health. The pattern of light and dark received at the eyes tunes our circadian system so we sleep better at night, feel refreshed and revitalized in the morning, and are better able to ward off physical and mental health problems like metabolic disease, cardiovascular disease, cancer, and depression. But, people living in nursing homes, who are often at elevated risk for experiencing these health problems, typically spend their days in constantly dim lighting conditions that can confound the benefits accorded by a healthy circadian system. Building on the Light and Health Research Center (LHRC) at Mount Sinai's general premise that an abundance of circadian-effective light in architectural spaces promotes good health, well-being and nighttime sleep (see the April/May issue of designing lighting), this article specifically focuses on an innovative application for bringing bright daytime light and better sleep to a senior living community.

Complexity of Application

Implementing a successful bright light design is no simple matter, mainly because delivering sufficient light from overhead luminaires to occupants' eyes for stimulating the circadian system can be challenging, costly, and energy-inefficient. In settings populated by older adults, delivering adequate light can be even more challenging, as pathologies of the aging eye (e.g., lens thickening, age-related macular degeneration, cataracts, etc.) can block the transmission of light to the part of the eye that receives light signals (i.e. the retina), and reduce stimulus to the circadian system’s clock in the brain. For this population, light levels sufficient for circadian system stimulation can exceed 500 lx at the eye, which is much higher than the light levels typically found in senior care facilities or in individuals’ homes (e.g. <50 lx from a floor lamp providing ambient illumination).

One solution proposed in a 2016 study (1) by researchers now at the LHRC was a light table to deliver bright light to residents in a senior home community. In a follow-up to that study, LHRC researchers partnered with members of the Abe’s Garden Memory Care facility in Nashville, Tennessee, to upgrade the lighting in a resident dining area. With overhead lighting renovations being off the table, another solution was needed to fulfill the design requirements for this permanent installation. Since light tables are not commercially available products, the team had to get creative.

Squaretable Discussion

The team partnered with furniture designer Dean Babin to custom build light tables for the upgrade. After many iterations and testing, we arrived at a simple solution that checked the boxes for all the design requirements.

The light table houses a 36” x 36” custom-sized, 4-edge-lit LED panel with a 3700 K source providing ~3735 lumens at 40 watts. Design features such as variable correlated color temperature, color tuning, dimming capabilities, and a programmable on/off switch were deemed needless expenses and unnecessary for achieving the project's goals.

Breakdown of the light table’s components and how they fit the design goals.

The amount of light that reaches the eye depends on multiple factors, such as a person’s proximity to the table and whether their gaze is directed forward or down at the table. At a height of 13” above the table, we measured 550 lx for a forward gaze straight across and above the table, and upwards of 1000 lux at the eye for a gaze directed at the center of the table. Testing a worse case of partial coverage of the table with four opaque dinner plates, the brightness levels for both gazes reduced by about 50%. We therefore recommended keeping any items on the tables to a minimum to decrease light loss from obstructions. With the amount of time spent at the tables and anticipating individuals would be looking down at their food or activity most of the time, we predicted that the light tables would provide enough light to stimulate the circadian clock and meet the UL 24480 design guidelines. (2)

A prototype was sent to Abe’s Garden to assess its acceptability before the rest of the light tables were manufactured. Feedback from staff and residents mentioned that the tables were comfortable to use, whether seated in a typical chair or wheelchair, and were not too bright or glary. Overall, the table was well received.

The Reality

Implementing designs into real-world applications is more complex than can appear on the surface, and the team ran into some snafus along the way. The electrical cords powering the table could create a trip hazard, for example, especially if the table were placed in the center of the room. One solution would be to position tables on the room’s perimeter. Alternatively, a battery tucked into the frame could be used for power, but that would add to the facility’s maintenance load and necessitate swapping out multiple batteries. Energizing the light tables for only a few hours in the morning would make the batteries last longer. Lastly, if the budget permits, the best solution may be to install floor receptacles at the light table locations.

Trying it Out

To determine the light tables’ long-term impact on the residents, the team conducted a 3-month lighting intervention with the light tables being energized from 6:00 a.m. – 6:00 p.m. This schedule would ensure that residents could receive the intervention at breakfast (as early as 7:00 AM), lunch (12:00 PM), and dinner (5:00 PM), as well as other occasional gatherings/ activities.

Following a week-long baseline assessment (W1), the participating residents were periodically exposed to the light table on a voluntary basis between the hours of 6:00 a.m. and 6:00 p.m., seven days per week, over the course of 3 months (months 1–3). Actigraphy data (keyed “Ag” in the diagram) were collected from participants at baseline (W1, keyed “B”) and over the course of 3 subsequent assessment weeks (W9, W13, and W17). Data were collected during the final assessment week (W17), 3-4 weeks after the light table intervention had ceased.

The team looked at the 3-month lighting intervention’s impact on sleep compared to a baseline period for 13 residents. They were asked to wear an actigraph (i.e., activity monitor) on their non-dominant wrist to collect data on their rest–activity rhythms. The actigraph data for the five participants who completed the study showed trends in the right direction: they fell asleep faster, woke up less frequently in the night, and had better sleep efficiency (i.e., percentage of time spent asleep while in bed). These very preliminary data are consistent with our research (1, 3-5) and what others (6-8) have found, but additional data should be collected to confirm these results, as the current results are not statistically significant.

Actigraphy results for selected sleep measures. Average sleep onset latency (top) shows that participants took about 13 minutes less time to fall asleep after 3 months of the lighting intervention, compared to baseline. The average wake after sleep onset (middle) reduced to 60 minutes, compared to 105 minutes during baseline. Additionally, sleep efficiency (bottom) increased as the intervention went on. For all results, at Week 17 after the washout period with no lights, values began to go back towards what was seen during the baseline assessment.

Take a Seat

Consistent with the other studies cited, it takes time for daily light/dark patterns to take effect on sleep. To be successful, continuous exposure to bright light during the day requires regularity; therefore, a permanent installation is necessary to make light a part of a daily routine. A light table is a great alternative to overhead lighting for providing circadian-effective light during the day. Installing light tables doesn’t require modifications to pre-existing electrical systems, and the movable tables provide flexibility in meeting the needs of various daily activities across multiple spaces. Unlike overhead lighting, which cannot always guarantee specified light levels at the eye depending on occupant positions, light tables can better ensure exposure to desired bright light in specific places at set times. These light tables are not only useful in senior homes, but an iteration could be explored to implement for adolescents in school experiencing morning tiredness from having delayed circadian rhythms (i.e., desire to go to bed later and get up later), or even office workers who need an extra boost of light in a windowless office. Let’s start thinking about innovative ways to introduce more light into people's lives!

Acknowledgements

The author would like to acknowledge Mariana Figueiro, David Pedler, Barbara Plitnick, Martin Overington, and Charlie Jarboe of the Light and Health Research Center for their technical and editorial support. The author would also like to thank Chris Coelho, Misty Hogan, and Lacola Parker of Abe’s Garden for their support on site, along with Dean Babin (deanbabin.com) for collaboration of the design and curating the light tables. This study was funded by Care Foundation of America. ■

References

1. Figueiro M, Plitnick B, Rea M. Research Note: A self-luminous light table for persons with Alzheimer’s disease. Lighting Research and Technology. 2016; 48: 253-259.

2. Underwriters Laboratories. Design Guideline for Promoting Circadian Entrainment with Light for Day-Active People, Design Guideline 24480, Edition 1. DG 24480. Northbrook, IL: Underwriters Laboratories, 2019.

3. Figueiro MG, Sahin L, Kalsher M, Plitnick B, Rea MS. Long-term, all-day exposure to circadian-effective light improves sleep, mood, and behavior in persons with dementia. Journal of Alzheimer's Disease Reports. 2020; 4: 297-312.

4. Figueiro MG, Plitnick B, Roohan C, Sahin L, Kalsher M, Rea MS. Effects of a tailored lighting intervention on sleep quality, rest–activity, mood, and behavior in older adults with Alzheimer’s disease and related dementias: A randomized clinical trial. Journal of Clinical Sleep Medicine. 2019; 15: 1757-1767.

5. Figueiro MG. Light, sleep and circadian rhythms in older adults with Alzheimer's disease and related dementias. Neurodegenerative Disease Management. 2017; 7: 119-145.

6. Shochat T, Martin J, Marler M, Ancoli-Israel S. Illumination levels in nursing home patients: Effects on sleep and activity rhythms. Journal of Sleep Research. 2000; 9: 373-379.

7. Shishegar N, Boubekri M, Stine-Morrow EAL, Rogers WA. Tuning environmental lighting improves objective and subjective sleep quality in older adults. Building and Environment. 2021; 204: 108096.

8. Sloane PD, Williams CS, Mitchell CM, Preisser JS, Wood W, Barrick AL, et al. Highintensity environmental light in dementia: Effect on sleep and activity. Journal of the American Geriatrics Society. 2007; 55: 1524-1533.