“…In particular, the studies were selected according to the datasets used and to characterize the most widespread and valuable sleep indexes extracted in literature. It is worth noting from the table that the studies based on EEG, ECG and PPG signals [ 32 , 36 , 57 , 58 , 59 , 60 , 61 , 62 ] can be used to extract valuable information on sleep stages or sleep apnea; however, they need higher computational cost and specialized devices for signal acquisition. On the other hand, other works based on motion signal from accelerometer and PBS [ 7 , 10 , 24 , 63 , 64 ] underline the advantage of causing low or mild discomfort to generally detect sleep and wake phases.…”