The impact of disturbed sleep on cognition and functional domains is vitally important to study in order to increase our understanding of Alzheimer's disease (AD) phenomenology. Research has shown that the severity of sleep disturbance and dementia advance in parallel and possibly in a manner amenable to therapeutic intervention. In AD, sleep disruption is characterized by changes in sleep architecture. It is our contention that neuropathology specific to AD alters the circadian system at the suprachiasmatic nucleus (SCN). Environmental light is the most powerful regulator of this circadian system,4,5 and is known to have a significant regulatory effect on pineal melatonin synthesis and secretion via the SCN and multisynaptic pathways downstream from the SCN. This study will explore further the efficacy of a particular type of therapeutic light intervention in regulating the circadian system in AD, using data analytic methods capable of detecting changes at multiple time scales. Our central hypothesis is that properly-timed light exposure in individuals with AD will synchronize disorganized circadian and sleep-wake rhythms and improve functional plasticity [approximate entropy (ApEn), fractal dimension (FD)], thereby resulting in increased sleep efficiency (SE), reductions in sleep fragmentation (SF), reduced excessive daytime sleepiness (EDS) and dementia-related behaviors, and improvements in cognition and other daytime behaviors. Women are nearly twice as likely as men to develop AD due to longer life expectance and emerging evidence. In light of this increased risk and also to enhance other aspects of biological uniformity in our study, this project will investigate women with AD.