Aging is one of the most significant factors associated with changes in sleep across the lifetime [1]. Sleep consists of two physiologically distinct states: rapid eye movement (REM) and non-rapid eye movements (NREM) sleep [1]. NREM sleep is associated with minimal mental activity and is divided into three stages, with increasing depth of sleep achieved from stages N1 through N3 (Figure 2.1). REM sleep consists of electroencephalography (EEG) activation, muscle atonia, and rapid eye movements. For most adult sleepers, sleep onset occurs through NREM sleep with REM sleep occurring at least 80 minutes afterwards and NREM and REM sleep typically alternating throughout the rest of the sleeping