Persons with Alzheimer’s disease and related dementias (ADRD) are often difficult to manage because of sleep problems, nocturnal wandering, and daytime irritability. Irregular activity-rest patterns, possibly due to disruption of circadian rhythms, are among the most common reasons for nursing home placement.
Circadian rhythms are governed by the master clock in the suprachiasmatic nuclei (SCN), which has an intrinsic period slightly longer than 24 hours. The light-dark pattern incident on the retina entrains the SCN to the 24-hour day, coordinating and enabling biological rhythms to occur at the correct time of day and night for species survival. Without exposure to a regular, daily pattern of light and dark, circadian rhythms become irregular, compromising health and well-being [1
Light treatment to promote circadian entrainment offers promise as a non-pharmacological method to regulate sleep and activity in persons with ADRD. Studies have shown that regular morning or evening light exposures, as well as all-day light exposures, can consolidate and improve nighttime sleep, increase daytime wakefulness, and reduce evening agitation [2
Research has shown that the human circadian system is maximally sensitive to 460 nm (blue) light [9
]. Few photometric instruments are calibrated in terms of “circadian light” and can record light over extended periods of time. Consequently, there have been few field studies quantifying light-dark exposure patterns as they might affect circadian disruption.
The present paper provides personal light-dark exposure patterns and activity-rest patterns exhibited by non-institutionalized persons with ADRD and by healthy older adults. From those data, levels of circadian disruption exhibited by healthy adults and by persons with ADRD are compared. Levels of circadian disruption exhibited by persons with ADRD during the winter and during the summer are also evaluated.