Two Circadian Lighting Studies

Two recent studies probed how circadian lighting influences the experiences of older individuals

Grant and colleagues investigated falls in care homes by elderly (mean age 81 +/- 12 years old) residents: some test locations “had solid-state lighting installed throughout the facility that changed in intensity and spectrum to increase short-wavelength (blue light) exposure during the day (6 am–6 pm) and decrease it overnight (6 pm–6 am). The control sites retained standard lighting with no change in intensity or spectrum throughout the day. The number of falls aggregated from medical records were assessed over an approximately 24-month interval. . . .  Before the lighting upgrade, the rate of falls was similar between experimental and control sites. . . . Following the upgrade, falls were reduced by 43% at experimental sites compared with control sites. . . . Upgrading ambient lighting to incorporate higher intensity blue-enriched white light during the daytime and lower intensity overnight represents an effective, passive, low-cost, low-burden addition to current preventive strategies to reduce fall risk in long-term care settings.”

Shishegar and Boubekri collected data in the homes of people averaging 77 years old and  report that “The lighting condition (LT) was designed to create a direct/indirect ambient illumination that delivered bright, blue-enriched light (illuminance level: 500 lx, Correlated Color Temperature (CCT): 6500 K) in the morning, followed by gradually lower illuminance levels and CCT throughout the rest of the day, reaching 100 lx and 2700 K in the evening. To further examine the effects of spectrum, we also included another lighting condition (LP) with the same range of illuminance levels and constant CCT of 2700 K from morning to evening. . . . Significant improvements were observed in mood and cognitive functions measured after exposure to both lighting conditions (LP and LT); there were significantly greater improvements for the LT as compared to the LP condition.”

Leila Grant, Melissa St. Hilaire, Jenna Heller, Rodney Heller, Steven Lockley, and Shadab Rahnman.  “Impact of Upgraded Lighting on Falls in Care Home Residents.”  The Journal of Post-Acute and Long-Term Care Medicine, in press, https://doi.org/10.1016/j.jamda.2022.06.013

 Nastaran Shishegar and Mohamed Boubekri. 2022. “Lighting Up Living Spaces to Improve Mood and Cognitive Performance in Older Adults.”  Journal of Environmental Psychology, vol. 82, 101845, https://doi.org/10.1016/j.jenvp.2022.101845