Strategies for optimizing light therapy efficacy in Alzheimer's disease patients

Abstract

Dependent variables gauging the performance of the novel luminaires include illuminance measured at the eye and corresponding circadian light (CLA) and circadian stimulus (CS) values. Parameters assessing the circadian efficacy of the luminaires include the inter-daily (IR) repeatability of the circadian rhythm, phasor magnitude, the average activity of the ten most active hours (M10), the average activity of the five least active hours (L5), relative amplitude (RA), PSQI scores, MDS-ADL scores, CSDD scores, and CMAI scores. Variables used to gauge the feasibility of using the Dimesimeter include comparisons between average eye-level illuminances, average wrist illuminances, average Dimesimeter-recorded illuminances, and all corresponding CLA and CS values.

The study took place in two assisted living facilities in New York's Albany County between the last weeks of November 2011 to the beginning of July 2012. A total of nine mild to moderate ADRD subjects were recruited, and a total of five subjects completed the study. Once recruited, baseline light and activity data were recorded using a wrist-mounted Dimesimeter for 7 days, and primary caregivers were asked to fill out a battery of tests including the Pittsburgh Sleep Quality Index (PSQI), the Minimum Data Set--Activities of Daily Living (MDS-ADL), the Cornell Scale for Depression in Dementia (CSDD) questionnaire, and the Cohen-Mansfield Aggression Index (CMAI). Afterwards, a lighting intervention of four 9325 K CCT novel circadian luminaires averaging 320 lux (CS= 0.46) at eye-level (altogether) were installed in the subjects' bedrooms for a total of 28 days. The final Dimesimeter and battery of tests was dispatched during the last 7 days of the intervention period for additional data collection. At the end of the 28 days, experimenters removed the novel luminaires, retrieved the Dimesimeter, and completed questionnaires.

Studies in the past have confirmed that light consolidates the rest/activity rhythms of Alzheimer's Disease and related dementia (ADRD) patients. Lighting interventions have also been shown to be a successful, non-pharmacological method to reduce depression, agitation, and increase independence in daily activities such as going to the bathroom. While this research continues to confirm the positive outcomes of circadian light therapy, researchers are no further along specifying a lighting dose. Light therapy apparatuses for the ADRD population have also yet to be improved. This study attempts to begin specifying the dose and examines the acceptability and performance of a novel lighting system for ADRD patients.

The outcome of this study indicated that the novel lighting system successfully consolidated rest/activity rhythms, reduced depression, and reasonably reduced agitated behaviors; however, it did not increase independence in the activities of daily living. Additionally, pros and cons of the dose delivery method and dose measurement are also discussed to advise future research on improving lighting dose delivery.