Mounting Evidence on the Relationship between Sleep and Alzheimer's Disease

The relationship between sleep and Alzheimer’s disease (AD) has become increasingly apparent in recent years with the results of new scientific investigations and with AD being viewed as a multidimensional disease. One of the aims of researchers and clinicians is to identify AD biomarkers in the preclinical phase of the disease. The histopathological signs of AD during this phase (e.g., deposition of insoluble plaques of extracellular beta amyloid (A β ) in the brain, aggregation of tau protein into intracellular neurofibrillary tangles [1] precede the appearance of cognitive symptoms by many years. The multidimensionality of AD means that modifiable factors contribute to the development and progression of this disease. Sleep has long been part of this scenario, given the high incidence of sleep disorders in the AD population [2]. The views of the research community towards AD and the experimental procedures employed have changed profoundly over the past 15 years. With regard to prevention and the preclinical phase of the disease, healthy elderly populations and populations with mild cognitive impairment (MCI) have become crucial targets of AD research. Moreover, longitudinal studies follow the evolution of normal and pathological ageing over time.