A dementia determination device in a dementia information output system includes an obtainer which obtains, on a per unit period basis, the result of measuring body motion of a user in a sleep time period； and an outputter which outputs dementia information indicating the likelihood that the user is developing a mild cognitive disorder based on the occurrence frequency of a unit period in which the magnitude of a difference between reference data on body motion of a healthy subject in a sleep time period and the result of measuring obtained by the obtainer exceeds a predetermined threshold value.
