This cognitive function reduction determination system (120) is provided with: an acquisition unit which daily acquires a sleep-time movement amount, which is the amount of bodily movement of the user during a sleep time range, and a non-sleep-time movement amount, which is the amount of bodily movement of the user during the time range other than the sleep time range; and a determination unit (122) which determines that the cognitive function of the user has decreased during a multiple-day determination period relative to a multiple-day comparison period prior to the determination period if the frequency of days during the determination period in which the movement amount ratio, that is, the ratio of the non-sleep-time movement amount to the sleep-time movement amount, falls below a prescribed ratio is higher than the frequency of days during the comparative period in which the movement amount ratio falls below a prescribed ratio.
COGNITIVE FUNCTION REDUCTION DETERMINATION SYSTEM