Spa bathing at night has been thought to improve sleeping conditions and symptoms of dementia such as restlessness, wandering, and aggression in patients in our nursing home with special needs for the aged. The present study investigated patient activity using a lifestyle measurement device (Kenz Lifecorder) to examine the effects of night bathing on senile dementia by more objective methods. Nine patients with senile dementia of the Alzheimer type staying in health facility for the elderly were studied. These patients' symptoms of dementia were already incurable but daily living activities somewhat remained. The patients were divided into a night bathing group (n=5) and daytime bathing group (n=4) to study patient activity using a Kenz Lifecorder for 14 weeks, that is one week before the start of bathing, 12 weeks with bathing, and 1 week after bathing. The night bathing group had a higher rate of activity than the daytime bathing group. When comparing the daytime of night bathing patients with the daytime bathing individually, the former displayed increased activity in the daytime. As a group, the night bathing group was found to show a significant increase in the amount of daytime activity. However, the statistical significance was reached after Weeks 9-10, so 2-3 months were required to change lifestyle rhythms. The authors hope that night bathing or night bathing assistance will be received favorably by the long-term care and health care insurance systems.