O3‐08‐03: Field measurements of circadian light exposures, activity levels and degrees of circadian entrainment in healthy older adults and in persons with Alzheimer's disease

Failure to entrain to a regular 24-hour cycle of light and dark contribute to poor and unconsolidated sleep in persons with Alzheimer's disease (AD). Circadian-effective light and circadian entrainment have not been widely measured in persons with AD in the field, so clinicians may have limited knowledge and confidence in prescribing light treatments to improve sleep quality in this population. The goal of this study was to measure and compare circadian light, activity and circadian entrainment in healthy older adults and in those with AD. 21 healthy adults 65 and older with no reported sleep problems and 18 persons diagnosed with AD wore calibrated light and activity measurement devices (Dimesimeters) worn as a pin, a pendant, or a wrist-watch for 5 consecutive days. The Dimesimeter measured the patterns of circadian light exposure and of activity, which provided a measure of circadian entrainment. Measures of circadian entrainment in healthy older adults calculated using phasor analysis were similar to those observed in day-shift workers (e.g., nurses and school teachers), while circadian entrainment in persons with AD were similar to those observed in rotating-shift workers, known to exhibit circadian disruption. Measures of activity consolidation (e.g., relative amplitude (RA)) calculated using the activity/rest and the light/dark patterns obtained with the Dimesimeter demonstrated that those diagnosed with AD were less consolidated than healthy older adults, exhibiting lower RA. Circadian disruption, as a result of reduced circadian light exposures during the daytime hours may be an underlying contribution to sleep problems commonly experienced by those with AD. The field-deployable devices and methods used in this study are useful tools to quantify circadian entrainment. The next step, which we are currently collecting data on, will be to determine if a lighting intervention tailored to increase circadian entrainment can increase sleep efficiency in persons with AD.