This study's main hypothesis is that a delivering a tailored lighting intervention (TLI) will provide a successful means for promoting circadian entrainment and treating metabolic disease and inflammation in patients with mild cognitive impairment (MCI) and Alzheimer's disease (AD) and Alzheimer's disease and related dementias (ADRD). As such, the proposed studies have the potential to provide important insights into the link between AD/ADRD and type 2 diabetes (T2DM) by identifying the disruption of circadian rhythms as a key component in the metabolic impairment. Preliminary data from ongoing studies demonstrates a beneficial effect of light treatment on sleep and depression. If positive results are observed, the potential also exists to transform the manner in which homes, assisted living facilities, and nursing homes are lighted by delivering a simple, practical, non-pharmacological intervention to promote entrainment, improve sleep, and reduce metabolic disease in AD and mild AD MCI patients. This randomized, placebo-controlled, crossover study involving 60 AD/ADRD patients who live in controlled environments (i.e., assisted living facilities and nursing homes), will investigate whether 8 weeks of exposure to a TLI designed to increase circadian entrainment improves sleep, mood, inflammatory markers, and metabolic control, compared to a control, circadian-inactive light.

Alzheimer's disease (AD) and type 2 diabetes (T2DM) pose linked, major threats to aging societies worldwide, but the relationship between these two diseases remains poorly understood. Hence, insulin resistance may account for the close epidemiological association between AD and T2DM. A major gap in the understanding of this association, however, is how brain insulin resistance develops in the context of AD. Studies show that circadian disruption impairs metabolic control and increases the risk for diabetes and obesity. Vice versa, disrupted sleep and depression are closely linked to impaired metabolic control and increased diabetes risk in the general population. Notably, AD is associated with circadian disruption, which may be amplified by exposure to irregular light-dark patterns or constant dim light. To what extent circadian disruption contributes to increased diabetes risk in AD remains unclear. Here, the investigator aims to test whether a novel tailored lighting intervention (TLI) designed to promote circadian entrainment in AD patients can improve metabolic control. Preliminary data from ongoing studies demonstrates a beneficial effect of light treatment on sleep and depression. Given the close association of sleep on metabolic control, these data support the hypothesis that light therapy that promotes entrainment can restore metabolic control in AD patients. Specifically, the investigator will test the efficacy of a practical, scientifically sophisticated 24-hour lighting system for increasing circadian entrainment in older adults with AD and related dementias (ADRD). The major goal is to demonstrate that a practical, effective, tailored, nonpharmacological intervention that promotes circadian entrainment can be used to improve sleep, reduce inflammation, and ameliorate glucose intolerance and insulin resistance in AD/ADRD patients.

Aim 1: Test if a TLI that promotes entrainment can improve sleep, depression, inflammation, and glucose tolerance in patients with moderate to late stages ADRD. In a randomized, placebo-controlled, crossover study involving 60 ADRD patients who live in controlled environments, the investigators will investigate whether an 8-week exposure to a TLI designed to increase circadian entrainment (urinary melatonin and activity-rest patterns) will improve inflammation and glucose tolerance (oral glucose tolerance test), and reduce sleep disturbances (actigraphy, Pittsburgh Sleep Quality Index, PSQI) and depressive symptoms (Cornell Scale for Depression in Dementia, CSDD) compared to a control, circadian-inactive light.

Inclusion Criteria:

• Diagnosis of mild to moderate Alzheimer's disease or related dementia,
• sleep disturbance as determined by a score ≥ 5 on the PSQI

Exclusion Criteria:

• insulin-dependent diabetes,
• urinary incontinence
• obstructing cataracts
• macular degeneration
• blindness
• severe sleep apnea or
• restless leg syndrome (RLS)