The one of initial symptom of dementia is 'Decrease of Living Motivation'. The previous study has proved that a living motivation has a positive correlation with activities of daily living. In this study, the authors developed a system based on internet of things platform to monitor change in activities of daily living for elderly people who living alone and verified three hypotheses on a relationship between decrease of living motivation and change in activities of daily living. We made experiment with one subject who lives alone for 10 weeks to monitor activities of daily living every day and conducted a questionnaire to measure the subject's living motivation once a week. From the experiment, the results were supported two hypotheses. With this result, we consider that the decrease of living motivation can be detected by monitoring the change in going out time.