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.