Association Between Cerebral Arterial Vascular Flow and Sleep Apnea in Neurodegenerative Alterations

Numerous studies pointed out the close relationship between sleep apnea and cognitive impairment. To the investigators' knowledge, no trials have assessed the existence of a relationship between the IAH index and the cerebral arterial blood flow rate (macrocirculation). Developments in magnetic resonance imaging (MRI) provide new insights into the quantitative study of blood flow through phase contrast MRI also called "flow MRI". The main hypothesis tested in this study is the existence of a relationship between OSAS and total cerebral arterial vascular inflow measured by PC-MRI (in mL/min) in the elderly population. * Primary outcome: The apnea/hypopnea index (measured by nocturnal respiratory polygraphy) and total arterial flow rate (measured by PC-MRI) * Secondary outcomes: 1. Measurement of arrhythmia 2. Measurement of arterial blood pressure