Alzheimer's disease (AD) is characterised by a progressive loss of memory and cognitive function. In the early stages of AD, there is a progressive accumulation of molecules: β-amyloid peptides (Aβ) in the brain. There is a link between the accumulation of Aβ peptides and the deterioration of sleep, but current knowledge does not confirmed this link. The objective of this study is to define whether there is a link between cognitive decline and sleep disorders. If a correlation is found, this could allow earlier treatment of sleep disorders in the longer term in order to slow the development of AD. Treatment protocols in the field of Alzheimer's disease (AD) are directed towards participants at risk of developing the disease, such as those who carry at least one ε4 allele on apolipoprotein E (APOE ε4). An individual with 2 ε4 copies has a 30-55% risk of developing AD with an age of onset around 68 years and a dose effect of the allele on risk and age of onset of symptoms.