Older adults with Alzheimer disease and related dementias (ADRD) experience severe dysfunctions of their sleep–wake and rest–activity patterns that clinically present as sundowning, excessive daytime sleepiness, nocturnal wandering, agitation, irritability, day–night reversal, and decreased cognitive functioning. Recent research suggests a bidirectional relationship between sleep disruption and the deposition of Amyloid beta. Sleep problems are exacerbated in those with ADRD, whose rest–activity rhythms can become less consolidated, as manifested in nocturnal wandering. This population is also at higher risk for depression and agitation behavior. These disturbances can lead to the placement of patients with ADRD in controlled environments, where they experience even greater inactivity and reduced exposure to daytime circadian-effective light, exacerbating their symptoms even further.
Daytime light exposure is the major synchronizer of circadian rhythms to the solar day, and light therapy has shown promise as a nonpharmacological treatment to help regulate sleep and improve cognition in patients with ADRD. Studies have demonstrated that daytime light exposure can consolidate and increase nighttime sleep efficiency, increase daytime wakefulness, and reduce evening agitation. Although a recent Cochrane review casts doubt on the efficacy of light therapy for improving sleep and behavior in patients with ADRD, carefully specified and implemented light can be a powerful nonpharmacological intervention for improving sleep, mood, and behavior in persons living with ADRD, as shown in previous studies employing a tailored lighting intervention (TLI) designed to maximally affect the circadian system.
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